Bug 1766045 - Adding mach command to generate UniFFI files r=glandium

Added `mach uniffi generate` which executes `uniffi-bindgen-gecko-js` to
generate UniFFI bindings. It's unfortunate that we need to check these
files in, but I couldn't figure out a way to auto-generate them as part
of the build process.

Adding `#include "nsIContent.h"` to dom/base/nsINodeList.h.  I think
that should have been present before, but things built okay because of
the way things got combined in the uniffied .cpp files. Adding these new
webIDL files bumped `NodeListBinding.cpp` to a new uniffied .cpp file
which caused the build to fail.

Differential Revision: https://phabricator.services.mozilla.com/D144468

build/mach_initialize.py

@@ -363,6 +363,9 @@ def initialize(topsrcdir):
         ),
         "esmify": MachCommandReference("tools/esmify/mach_commands.py"),
         "xpcshell": MachCommandReference("js/xpconnect/mach_commands.py"),
+        "uniffi": MachCommandReference(
+            "toolkit/components/uniffi-bindgen-gecko-js/mach_commands.py"
+        ),
     }
 
     # Set a reasonable limit to the number of open files.

dom/base/nsINodeList.h

@@ -9,6 +9,7 @@
 
 #include "nsWrapperCache.h"
 #include "nsISupports.h"
+#include "nsIContent.h"
 
 // IID for the nsINodeList interface
 #define NS_INODELIST_IID                             \

toolkit/components/moz.build

@@ -143,3 +143,6 @@ if CONFIG["COMPILE_ENVIRONMENT"]:
     EXPORTS.mozilla += [
         "!regex_ffi_generated.h",
     ]
+
+if CONFIG["MOZ_UNIFFI_FIXTURES"]:
+    DIRS += ["uniffi-bindgen-gecko-js/fixtures"]

toolkit/components/uniffi-bindgen-gecko-js/fixtures/README.md

@@ -0,0 +1,36 @@
+This directory contains generated code for the UniFFI examples/fixtures and JS
+unit tests for it.
+
+This is only built if the `--enable-uniffi-fixtures` flag is present in
+`mozconfig`.  There's no benefit to including this in a release build.
+
+To add additional examples/fixtures:
+  - For most of these steps, find the code for existing fixtures and use it as a template for the new code.
+  - Edit `toolkit/components/uniffi-bindgen-gecko-js/mach_commands.py`
+    - Add an entry to `FIXTURE_UDL_FILES`
+  - Edit `toolkit/library/rust/shared/Cargo.toml`
+    - Add an optional dependency for the fixture.
+    - Add the feature to the list of features enabled by `uniffi_fixtures`.
+  - Edit `toolkit/library/rust/shared/lib.rs`:
+     - Add an `extern crate [name]` to the `uniffi_fixtures` mod
+       - Note: [name] is the name from the `[lib]` section in the Cargo.toml
+         for the example/fixture crate.  This does not always match the package
+         name for the crate.
+     - Add `[name]::reexport_uniffi_scaffolding` to the `uniffi_fixtures` mod
+  - Edit `toolkit/components/uniffi-bindgen-gecko-js/fixtures/moz.build` and add the fixture name to the `components`
+    list.
+  - Add a test module to the `toolkit/components/uniffi-bindgen-gecko-js/fixtures/tests/` directory and an entry for it
+    in `toolkit/components/uniffi-bindgen-gecko-js/fixtures/tests/xpcshell.ini`
+  - Run `mach vendor rust` to vendor in the Rust code.
+  - Run `mach uniffi generate` to generate the scaffolding code.
+  - Check in any new files
+
+To run the tests:
+  - Make sure you have a `mozconfig` file containing the line `ac_add_options --enable-uniffi-fixtures`
+  - Run `mach uniffi generate` if:
+    - You've added or updated a fixture
+    - You've made changes to `uniffi-bindgen-gecko-js`
+  - Run `mach build`
+  - Run `mach xpcshell-test toolkit/components/uniffi-bindgen-gecko-js/fixtures/tests/`
+    - You can also use a path to specific test file
+    - For subsequent runs, if you only modify the test files, then you can re-run this step directly

toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/Arithmetic.jsm

@@ -0,0 +1,401 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+
+
+"use strict";
+
+var EXPORTED_SYMBOLS = [];
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    static checkType(name, value) {
+        if (value === undefined ) {
+            throw TypeError(`${name} is undefined`);
+        }
+        if (value === null ) {
+            throw TypeError(`${name} is null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+
+class FfiConverterU64 extends FfiConverter {
+    static checkType(name, value) {
+        super.checkType(name, value);
+        if (!Number.isSafeInteger(value)) {
+            throw TypeError(`${name} exceeds the safe integer bounds (${value})`);
+        }
+        if (value < 0) {
+            throw TypeError(`${name} exceeds the U64 bounds (${value})`);
+        }
+    }
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readUint64()
+    }
+}class FfiConverterBool extends FfiConverter {
+    static computeSize() {
+        return 1;
+    }
+    static lift(value) {
+        return value == 1;
+    }
+    static lower(value) {
+        if (value) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+    static write(dataStream, value) {
+        dataStream.writeUint8(this.lower(value))
+    }
+    static read(dataStream) {
+        return this.lift(dataStream.readUint8())
+    }
+}
+
+class FfiConverterString extends FfiConverter {
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+
+class ArithmeticError extends Error {}
+EXPORTED_SYMBOLS.push("ArithmeticError");
+
+
+class IntegerOverflow extends ArithmeticError {
+    
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+}
+EXPORTED_SYMBOLS.push("IntegerOverflow");
+
+class FfiConverterTypeArithmeticError extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return new IntegerOverflow(FfiConverterString.read(dataStream));
+            default:
+                return new Error("Unknown ArithmeticError variant");
+        }
+    }
+}
+
+
+
+
+function add(a,b) {
+    
+    const liftResult = (result) => FfiConverterU64.lift(result);
+    const liftError = (data) => FfiConverterTypeArithmeticError.lift(data);
+    const functionCall = () => {
+        FfiConverterU64.checkType("a", a);
+        FfiConverterU64.checkType("b", b);
+        return UniFFIScaffolding.callAsync(
+            2, // arithmetic:arithmetic_77d6_add
+            FfiConverterU64.lower(a),
+            FfiConverterU64.lower(b),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("add");
+function sub(a,b) {
+    
+    const liftResult = (result) => FfiConverterU64.lift(result);
+    const liftError = (data) => FfiConverterTypeArithmeticError.lift(data);
+    const functionCall = () => {
+        FfiConverterU64.checkType("a", a);
+        FfiConverterU64.checkType("b", b);
+        return UniFFIScaffolding.callAsync(
+            3, // arithmetic:arithmetic_77d6_sub
+            FfiConverterU64.lower(a),
+            FfiConverterU64.lower(b),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("sub");
+function div(dividend,divisor) {
+    
+    const liftResult = (result) => FfiConverterU64.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterU64.checkType("dividend", dividend);
+        FfiConverterU64.checkType("divisor", divisor);
+        return UniFFIScaffolding.callAsync(
+            4, // arithmetic:arithmetic_77d6_div
+            FfiConverterU64.lower(dividend),
+            FfiConverterU64.lower(divisor),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("div");
+function equal(a,b) {
+    
+    const liftResult = (result) => FfiConverterBool.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterU64.checkType("a", a);
+        FfiConverterU64.checkType("b", b);
+        return UniFFIScaffolding.callAsync(
+            5, // arithmetic:arithmetic_77d6_equal
+            FfiConverterU64.lower(a),
+            FfiConverterU64.lower(b),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("equal");

toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/Geometry.jsm

@@ -0,0 +1,427 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+
+
+"use strict";
+
+var EXPORTED_SYMBOLS = [];
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    static checkType(name, value) {
+        if (value === undefined ) {
+            throw TypeError(`${name} is undefined`);
+        }
+        if (value === null ) {
+            throw TypeError(`${name} is null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+
+class FfiConverterF64 extends FfiConverter {
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat64()
+    }
+}
+
+class FfiConverterString extends FfiConverter {
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+class Line {
+    constructor(start,end) {
+        FfiConverterTypePoint.checkType("start", start);
+        FfiConverterTypePoint.checkType("end", end);
+        this.start = start;
+        this.end = end;
+    }
+    equals(other) {
+        return (
+            this.start.equals(other.start) &&
+            this.end.equals(other.end)
+        )
+    }
+}
+
+class FfiConverterTypeLine extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+    static read(dataStream) {
+        return new Line(
+            FfiConverterTypePoint.read(dataStream), 
+            FfiConverterTypePoint.read(dataStream)
+        );
+    }
+    static write(dataStream, value) {
+        FfiConverterTypePoint.write(dataStream, value.start);
+        FfiConverterTypePoint.write(dataStream, value.end);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterTypePoint.computeSize(value.start);
+        totalSize += FfiConverterTypePoint.computeSize(value.end);
+        return totalSize
+    }
+}
+
+EXPORTED_SYMBOLS.push("Line");
+
+class Point {
+    constructor(coordX,coordY) {
+        FfiConverterF64.checkType("coordX", coordX);
+        FfiConverterF64.checkType("coordY", coordY);
+        this.coordX = coordX;
+        this.coordY = coordY;
+    }
+    equals(other) {
+        return (
+            this.coordX == other.coordX &&
+            this.coordY == other.coordY
+        )
+    }
+}
+
+class FfiConverterTypePoint extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+    static read(dataStream) {
+        return new Point(
+            FfiConverterF64.read(dataStream), 
+            FfiConverterF64.read(dataStream)
+        );
+    }
+    static write(dataStream, value) {
+        FfiConverterF64.write(dataStream, value.coordX);
+        FfiConverterF64.write(dataStream, value.coordY);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterF64.computeSize(value.coordX);
+        totalSize += FfiConverterF64.computeSize(value.coordY);
+        return totalSize
+    }
+}
+
+EXPORTED_SYMBOLS.push("Point");class FfiConverterOptionalTypePoint extends FfiConverterArrayBuffer {
+    static checkType(name, value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypePoint.checkType(name, value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypePoint.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypePoint.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypePoint.computeSize(value)
+    }
+}
+
+
+function gradient(ln) {
+    
+    const liftResult = (result) => FfiConverterF64.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypeLine.checkType("ln", ln);
+        return UniFFIScaffolding.callAsync(
+            0, // geometry:geometry_ba8c_gradient
+            FfiConverterTypeLine.lower(ln),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("gradient");
+function intersection(ln1,ln2) {
+    
+    const liftResult = (result) => FfiConverterOptionalTypePoint.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypeLine.checkType("ln1", ln1);
+        FfiConverterTypeLine.checkType("ln2", ln2);
+        return UniFFIScaffolding.callAsync(
+            1, // geometry:geometry_ba8c_intersection
+            FfiConverterTypeLine.lower(ln1),
+            FfiConverterTypeLine.lower(ln2),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("intersection");

toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/README.md

@@ -0,0 +1 @@
+This directory is where files generated by Uniffi will be created.

toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/Sprites.jsm

@@ -0,0 +1,561 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+
+
+"use strict";
+
+var EXPORTED_SYMBOLS = [];
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+
+    // Reads a Sprite pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerSprite() {
+        const pointerId = 3; // sprites:Sprite
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a Sprite pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerSprite(value) {
+        const pointerId = 3; // sprites:Sprite
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    static checkType(name, value) {
+        if (value === undefined ) {
+            throw TypeError(`${name} is undefined`);
+        }
+        if (value === null ) {
+            throw TypeError(`${name} is null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+
+class FfiConverterF64 extends FfiConverter {
+    static computeSize() {
+        return 8;
+    }
+    static lift(value) {
+        return value;
+    }
+    static lower(value) {
+        return value;
+    }
+    static write(dataStream, value) {
+        dataStream.writeFloat64(value)
+    }
+    static read(dataStream) {
+        return dataStream.readFloat64()
+    }
+}
+
+class FfiConverterString extends FfiConverter {
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+
+class Sprite {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for Sprite.
+     * 
+     * @returns {Promise<Sprite>}: A promise that resolves
+     *      to a newly constructed Sprite
+     */
+    static init(initialPosition) {
+    const liftResult = (result) => FfiConverterTypeSprite.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterOptionalTypePoint.checkType("initialPosition", initialPosition);
+        return UniFFIScaffolding.callAsync(
+            66, // sprites:sprites_f59e_Sprite_new
+            FfiConverterOptionalTypePoint.lower(initialPosition),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    /**
+     * An async constructor for Sprite.
+     * 
+     * @returns {Promise<Sprite>}: A promise that resolves
+     *      to a newly constructed Sprite
+     */
+    static newRelativeTo(reference,direction) {
+    const liftResult = (result) => FfiConverterTypeSprite.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypePoint.checkType("reference", reference);
+        FfiConverterTypeVector.checkType("direction", direction);
+        return UniFFIScaffolding.callAsync(
+            67, // sprites:sprites_f59e_Sprite_new_relative_to
+            FfiConverterTypePoint.lower(reference),
+            FfiConverterTypeVector.lower(direction),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    getPosition() {
+    const liftResult = (result) => FfiConverterTypePoint.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            68, // sprites:sprites_f59e_Sprite_get_position
+            FfiConverterTypeSprite.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    moveTo(position) {
+    const liftResult = (result) => undefined;
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypePoint.checkType("position", position);
+        return UniFFIScaffolding.callAsync(
+            69, // sprites:sprites_f59e_Sprite_move_to
+            FfiConverterTypeSprite.lower(this),
+            FfiConverterTypePoint.lower(position),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    moveBy(direction) {
+    const liftResult = (result) => undefined;
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypeVector.checkType("direction", direction);
+        return UniFFIScaffolding.callAsync(
+            70, // sprites:sprites_f59e_Sprite_move_by
+            FfiConverterTypeSprite.lower(this),
+            FfiConverterTypeVector.lower(direction),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+
+}
+
+class FfiConverterTypeSprite extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new Sprite(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerSprite());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerSprite(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+EXPORTED_SYMBOLS.push("Sprite");
+
+class Point {
+    constructor(x,y) {
+        FfiConverterF64.checkType("x", x);
+        FfiConverterF64.checkType("y", y);
+        this.x = x;
+        this.y = y;
+    }
+    equals(other) {
+        return (
+            this.x == other.x &&
+            this.y == other.y
+        )
+    }
+}
+
+class FfiConverterTypePoint extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+    static read(dataStream) {
+        return new Point(
+            FfiConverterF64.read(dataStream), 
+            FfiConverterF64.read(dataStream)
+        );
+    }
+    static write(dataStream, value) {
+        FfiConverterF64.write(dataStream, value.x);
+        FfiConverterF64.write(dataStream, value.y);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterF64.computeSize(value.x);
+        totalSize += FfiConverterF64.computeSize(value.y);
+        return totalSize
+    }
+}
+
+EXPORTED_SYMBOLS.push("Point");
+
+class Vector {
+    constructor(dx,dy) {
+        FfiConverterF64.checkType("dx", dx);
+        FfiConverterF64.checkType("dy", dy);
+        this.dx = dx;
+        this.dy = dy;
+    }
+    equals(other) {
+        return (
+            this.dx == other.dx &&
+            this.dy == other.dy
+        )
+    }
+}
+
+class FfiConverterTypeVector extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+    static read(dataStream) {
+        return new Vector(
+            FfiConverterF64.read(dataStream), 
+            FfiConverterF64.read(dataStream)
+        );
+    }
+    static write(dataStream, value) {
+        FfiConverterF64.write(dataStream, value.dx);
+        FfiConverterF64.write(dataStream, value.dy);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterF64.computeSize(value.dx);
+        totalSize += FfiConverterF64.computeSize(value.dy);
+        return totalSize
+    }
+}
+
+EXPORTED_SYMBOLS.push("Vector");class FfiConverterOptionalTypePoint extends FfiConverterArrayBuffer {
+    static checkType(name, value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypePoint.checkType(name, value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypePoint.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypePoint.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypePoint.computeSize(value)
+    }
+}
+
+
+function translate(position,direction) {
+    
+    const liftResult = (result) => FfiConverterTypePoint.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypePoint.checkType("position", position);
+        FfiConverterTypeVector.checkType("direction", direction);
+        return UniFFIScaffolding.callAsync(
+            71, // sprites:sprites_f59e_translate
+            FfiConverterTypePoint.lower(position),
+            FfiConverterTypeVector.lower(direction),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("translate");

toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated/Todolist.jsm

@@ -0,0 +1,737 @@
+// This file was autogenerated by the `uniffi-bindgen-gecko-js` crate.
+// Trust me, you don't want to mess with it!
+
+
+
+"use strict";
+
+var EXPORTED_SYMBOLS = [];
+
+// Write/Read data to/from an ArrayBuffer
+class ArrayBufferDataStream {
+    constructor(arrayBuffer) {
+        this.dataView = new DataView(arrayBuffer);
+        this.pos = 0;
+    }
+
+    readUint8() {
+        let rv = this.dataView.getUint8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeUint8(value) {
+        this.dataView.setUint8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readUint16() {
+        let rv = this.dataView.getUint16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeUint16(value) {
+        this.dataView.setUint16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readUint32() {
+        let rv = this.dataView.getUint32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeUint32(value) {
+        this.dataView.setUint32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readUint64() {
+        let rv = this.dataView.getBigUint64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeUint64(value) {
+        this.dataView.setBigUint64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readInt8() {
+        let rv = this.dataView.getInt8(this.pos);
+        this.pos += 1;
+        return rv;
+    }
+
+    writeInt8(value) {
+        this.dataView.setInt8(this.pos, value);
+        this.pos += 1;
+    }
+
+    readInt16() {
+        let rv = this.dataView.getInt16(this.pos);
+        this.pos += 2;
+        return rv;
+    }
+
+    writeInt16(value) {
+        this.dataView.setInt16(this.pos, value);
+        this.pos += 2;
+    }
+
+    readInt32() {
+        let rv = this.dataView.getInt32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeInt32(value) {
+        this.dataView.setInt32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readInt64() {
+        let rv = this.dataView.getBigInt64(this.pos);
+        this.pos += 8;
+        return Number(rv);
+    }
+
+    writeInt64(value) {
+        this.dataView.setBigInt64(this.pos, BigInt(value));
+        this.pos += 8;
+    }
+
+
+    readFloat32() {
+        let rv = this.dataView.getFloat32(this.pos);
+        this.pos += 4;
+        return rv;
+    }
+
+    writeFloat32(value) {
+        this.dataView.setFloat32(this.pos, value);
+        this.pos += 4;
+    }
+
+    readFloat64() {
+        let rv = this.dataView.getFloat64(this.pos);
+        this.pos += 8;
+        return rv;
+    }
+
+    writeFloat64(value) {
+        this.dataView.setFloat64(this.pos, value);
+        this.pos += 8;
+    }
+
+
+    writeString(value) {
+      const encoder = new TextEncoder();
+      // Note: in order to efficiently write this data, we first write the
+      // string data, reserving 4 bytes for the size.
+      const dest = new Uint8Array(this.dataView.buffer, this.pos + 4);
+      const encodeResult = encoder.encodeInto(value, dest);
+      if (encodeResult.read != value.length) {
+        throw new UniFFIError(
+            "writeString: out of space when writing to ArrayBuffer.  Did the computeSize() method returned the wrong result?"
+        );
+      }
+      const size = encodeResult.written;
+      // Next, go back and write the size before the string data
+      this.dataView.setUint32(this.pos, size);
+      // Finally, advance our position past both the size and string data
+      this.pos += size + 4;
+    }
+
+    readString() {
+      const decoder = new TextDecoder();
+      const size = this.readUint32();
+      const source = new Uint8Array(this.dataView.buffer, this.pos, size)
+      const value = decoder.decode(source);
+      this.pos += size;
+      return value;
+    }
+
+    // Reads a TodoList pointer from the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    readPointerTodoList() {
+        const pointerId = 4; // todolist:TodoList
+        const res = UniFFIScaffolding.readPointer(pointerId, this.dataView.buffer, this.pos);
+        this.pos += 8;
+        return res;
+    }
+
+    // Writes a TodoList pointer into the data stream
+    // UniFFI Pointers are **always** 8 bytes long. That is enforced
+    // by the C++ and Rust Scaffolding code.
+    writePointerTodoList(value) {
+        const pointerId = 4; // todolist:TodoList
+        UniFFIScaffolding.writePointer(pointerId, value, this.dataView.buffer, this.pos);
+        this.pos += 8;
+    }
+    
+}
+
+function handleRustResult(result, liftCallback, liftErrCallback) {
+    switch (result.code) {
+        case "success":
+            return liftCallback(result.data);
+
+        case "error":
+            throw liftErrCallback(result.data);
+
+        case "internal-error":
+            let message = result.internalErrorMessage;
+            if (message) {
+                throw new UniFFIInternalError(message);
+            } else {
+                throw new UniFFIInternalError("Unknown error");
+            }
+
+        default:
+            throw new UniFFIError(`Unexpected status code: ${result.code}`);
+    }
+}
+
+class UniFFIError {
+    constructor(message) {
+        this.message = message;
+    }
+}
+
+class UniFFIInternalError extends UniFFIError {}
+
+// Base class for FFI converters
+class FfiConverter {
+    static checkType(name, value) {
+        if (value === undefined ) {
+            throw TypeError(`${name} is undefined`);
+        }
+        if (value === null ) {
+            throw TypeError(`${name} is null`);
+        }
+    }
+}
+
+// Base class for FFI converters that lift/lower by reading/writing to an ArrayBuffer
+class FfiConverterArrayBuffer extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+}
+
+// Symbols that are used to ensure that Object constructors
+// can only be used with a proper UniFFI pointer
+const uniffiObjectPtr = Symbol("uniffiObjectPtr");
+const constructUniffiObject = Symbol("constructUniffiObject");
+
+
+
+class FfiConverterString extends FfiConverter {
+    static lift(buf) {
+        const decoder = new TextDecoder();
+        const utf8Arr = new Uint8Array(buf);
+        return decoder.decode(utf8Arr);
+    }
+    static lower(value) {
+        const encoder = new TextEncoder();
+        return encoder.encode(value).buffer;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeString(value);
+    }
+
+    static read(dataStream) {
+        return dataStream.readString();
+    }
+
+    static computeSize(value) {
+        const encoder = new TextEncoder();
+        return 4 + encoder.encode(value).length
+    }
+}
+
+
+class TodoList {
+    // Use `init` to instantiate this class.
+    // DO NOT USE THIS CONSTRUCTOR DIRECTLY
+    constructor(opts) {
+        if (!Object.prototype.hasOwnProperty.call(opts, constructUniffiObject)) {
+            throw new UniFFIError("Attempting to construct an object using the JavaScript constructor directly" +
+            "Please use a UDL defined constructor, or the init function for the primary constructor")
+        }
+        if (!opts[constructUniffiObject] instanceof UniFFIPointer) {
+            throw new UniFFIError("Attempting to create a UniFFI object with a pointer that is not an instance of UniFFIPointer")
+        }
+        this[uniffiObjectPtr] = opts[constructUniffiObject];
+    }
+    /**
+     * An async constructor for TodoList.
+     * 
+     * @returns {Promise<TodoList>}: A promise that resolves
+     *      to a newly constructed TodoList
+     */
+    static init() {
+    const liftResult = (result) => FfiConverterTypeTodoList.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            72, // todolist:todolist_9473_TodoList_new
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    addItem(todo) {
+    const liftResult = (result) => undefined;
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        FfiConverterString.checkType("todo", todo);
+        return UniFFIScaffolding.callAsync(
+            73, // todolist:todolist_9473_TodoList_add_item
+            FfiConverterTypeTodoList.lower(this),
+            FfiConverterString.lower(todo),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    addEntry(entry) {
+    const liftResult = (result) => undefined;
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        FfiConverterTypeTodoEntry.checkType("entry", entry);
+        return UniFFIScaffolding.callAsync(
+            74, // todolist:todolist_9473_TodoList_add_entry
+            FfiConverterTypeTodoList.lower(this),
+            FfiConverterTypeTodoEntry.lower(entry),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    getEntries() {
+    const liftResult = (result) => FfiConverterSequenceTypeTodoEntry.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            75, // todolist:todolist_9473_TodoList_get_entries
+            FfiConverterTypeTodoList.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    getItems() {
+    const liftResult = (result) => FfiConverterSequencestring.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            76, // todolist:todolist_9473_TodoList_get_items
+            FfiConverterTypeTodoList.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    addEntries(entries) {
+    const liftResult = (result) => undefined;
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterSequenceTypeTodoEntry.checkType("entries", entries);
+        return UniFFIScaffolding.callAsync(
+            77, // todolist:todolist_9473_TodoList_add_entries
+            FfiConverterTypeTodoList.lower(this),
+            FfiConverterSequenceTypeTodoEntry.lower(entries),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    addItems(items) {
+    const liftResult = (result) => undefined;
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterSequencestring.checkType("items", items);
+        return UniFFIScaffolding.callAsync(
+            78, // todolist:todolist_9473_TodoList_add_items
+            FfiConverterTypeTodoList.lower(this),
+            FfiConverterSequencestring.lower(items),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    getLastEntry() {
+    const liftResult = (result) => FfiConverterTypeTodoEntry.lift(result);
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            79, // todolist:todolist_9473_TodoList_get_last_entry
+            FfiConverterTypeTodoList.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    getLast() {
+    const liftResult = (result) => FfiConverterString.lift(result);
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            80, // todolist:todolist_9473_TodoList_get_last
+            FfiConverterTypeTodoList.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    getFirst() {
+    const liftResult = (result) => FfiConverterString.lift(result);
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            81, // todolist:todolist_9473_TodoList_get_first
+            FfiConverterTypeTodoList.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    clearItem(todo) {
+    const liftResult = (result) => undefined;
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        FfiConverterString.checkType("todo", todo);
+        return UniFFIScaffolding.callAsync(
+            82, // todolist:todolist_9473_TodoList_clear_item
+            FfiConverterTypeTodoList.lower(this),
+            FfiConverterString.lower(todo),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+    makeDefault() {
+    const liftResult = (result) => undefined;
+    const liftError = null;
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            83, // todolist:todolist_9473_TodoList_make_default
+            FfiConverterTypeTodoList.lower(this),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }}
+
+}
+
+class FfiConverterTypeTodoList extends FfiConverter {
+    static lift(value) {
+        const opts = {};
+        opts[constructUniffiObject] = value;
+        return new TodoList(opts);
+    }
+
+    static lower(value) {
+        return value[uniffiObjectPtr];
+    }
+
+    static read(dataStream) {
+        return this.lift(dataStream.readPointerTodoList());
+    }
+
+    static write(dataStream, value) {
+        dataStream.writePointerTodoList(value[uniffiObjectPtr]);
+    }
+
+    static computeSize(value) {
+        return 8;
+    }
+}
+
+EXPORTED_SYMBOLS.push("TodoList");
+
+class TodoEntry {
+    constructor(text) {
+        FfiConverterString.checkType("text", text);
+        this.text = text;
+    }
+    equals(other) {
+        return (
+            this.text == other.text
+        )
+    }
+}
+
+class FfiConverterTypeTodoEntry extends FfiConverter {
+    static lift(buf) {
+        return this.read(new ArrayBufferDataStream(buf));
+    }
+    static lower(value) {
+        const buf = new ArrayBuffer(this.computeSize(value));
+        const dataStream = new ArrayBufferDataStream(buf);
+        this.write(dataStream, value);
+        return buf;
+    }
+    static read(dataStream) {
+        return new TodoEntry(
+            FfiConverterString.read(dataStream)
+        );
+    }
+    static write(dataStream, value) {
+        FfiConverterString.write(dataStream, value.text);
+    }
+
+    static computeSize(value) {
+        let totalSize = 0;
+        totalSize += FfiConverterString.computeSize(value.text);
+        return totalSize
+    }
+}
+
+EXPORTED_SYMBOLS.push("TodoEntry");
+
+
+class TodoError extends Error {}
+EXPORTED_SYMBOLS.push("TodoError");
+
+
+class TodoDoesNotExist extends TodoError {
+    
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+}
+EXPORTED_SYMBOLS.push("TodoDoesNotExist");
+class EmptyTodoList extends TodoError {
+    
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+}
+EXPORTED_SYMBOLS.push("EmptyTodoList");
+class DuplicateTodo extends TodoError {
+    
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+}
+EXPORTED_SYMBOLS.push("DuplicateTodo");
+class EmptyString extends TodoError {
+    
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+}
+EXPORTED_SYMBOLS.push("EmptyString");
+class DeligatedError extends TodoError {
+    
+    constructor(message, ...params) {
+        super(...params);
+        this.message = message;
+    }
+}
+EXPORTED_SYMBOLS.push("DeligatedError");
+
+class FfiConverterTypeTodoError extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        switch (dataStream.readInt32()) {
+            case 1:
+                return new TodoDoesNotExist(FfiConverterString.read(dataStream));
+            case 2:
+                return new EmptyTodoList(FfiConverterString.read(dataStream));
+            case 3:
+                return new DuplicateTodo(FfiConverterString.read(dataStream));
+            case 4:
+                return new EmptyString(FfiConverterString.read(dataStream));
+            case 5:
+                return new DeligatedError(FfiConverterString.read(dataStream));
+            default:
+                return new Error("Unknown TodoError variant");
+        }
+    }
+}
+
+class FfiConverterOptionalTypeTodoList extends FfiConverterArrayBuffer {
+    static checkType(name, value) {
+        if (value !== undefined && value !== null) {
+            FfiConverterTypeTodoList.checkType(name, value)
+        }
+    }
+
+    static read(dataStream) {
+        const code = dataStream.readUint8(0);
+        switch (code) {
+            case 0:
+                return null
+            case 1:
+                return FfiConverterTypeTodoList.read(dataStream)
+            default:
+                throw UniFFIError(`Unexpected code: ${code}`);
+        }
+    }
+
+    static write(dataStream, value) {
+        if (value === null || value === undefined) {
+            dataStream.writeUint8(0);
+            return;
+        }
+        dataStream.writeUint8(1);
+        FfiConverterTypeTodoList.write(dataStream, value)
+    }
+
+    static computeSize(value) {
+        if (value === null || value === undefined) {
+            return 1;
+        }
+        return 1 + FfiConverterTypeTodoList.computeSize(value)
+    }
+}class FfiConverterSequencestring extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterString.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterString.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterString.computeSize(innerValue);
+        }
+        return size;
+    }
+}class FfiConverterSequenceTypeTodoEntry extends FfiConverterArrayBuffer {
+    static read(dataStream) {
+        const len = dataStream.readInt32();
+        const arr = [];
+        for (let i = 0; i < len; i++) {
+            arr.push(FfiConverterTypeTodoEntry.read(dataStream));
+        }
+        return arr;
+    }
+
+    static write(dataStream, value) {
+        dataStream.writeInt32(value.length);
+        value.forEach((innerValue) => {
+            FfiConverterTypeTodoEntry.write(dataStream, innerValue);
+        })
+    }
+
+    static computeSize(value) {
+        // The size of the length
+        let size = 4;
+        for (const innerValue of value) {
+            size += FfiConverterTypeTodoEntry.computeSize(innerValue);
+        }
+        return size;
+    }
+}
+
+
+function getDefaultList() {
+    
+    const liftResult = (result) => FfiConverterOptionalTypeTodoList.lift(result);
+    const liftError = null;
+    const functionCall = () => {
+        return UniFFIScaffolding.callAsync(
+            84, // todolist:todolist_9473_get_default_list
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("getDefaultList");
+function setDefaultList(list) {
+    
+    const liftResult = (result) => undefined;
+    const liftError = null;
+    const functionCall = () => {
+        FfiConverterTypeTodoList.checkType("list", list);
+        return UniFFIScaffolding.callAsync(
+            85, // todolist:todolist_9473_set_default_list
+            FfiConverterTypeTodoList.lower(list),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("setDefaultList");
+function createEntryWith(todo) {
+    
+    const liftResult = (result) => FfiConverterTypeTodoEntry.lift(result);
+    const liftError = (data) => FfiConverterTypeTodoError.lift(data);
+    const functionCall = () => {
+        FfiConverterString.checkType("todo", todo);
+        return UniFFIScaffolding.callAsync(
+            86, // todolist:todolist_9473_create_entry_with
+            FfiConverterString.lower(todo),
+        )
+    }
+    try {
+        return functionCall().then((result) => handleRustResult(result, liftResult, liftError));
+    }  catch (error) {
+        return Promise.reject(error)
+    }
+}
+
+EXPORTED_SYMBOLS.push("createEntryWith");

toolkit/components/uniffi-bindgen-gecko-js/fixtures/moz.build

@@ -0,0 +1,19 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+FINAL_LIBRARY = "xul"
+
+components = [
+    "Arithmetic",
+    "Geometry",
+    "Rondpoint",
+    "Sprites",
+    "Todolist",
+]
+
+EXTRA_JS_MODULES["components-utils"] = [
+    "generated/{}.jsm".format(component) for component in components
+]

toolkit/components/uniffi-bindgen-gecko-js/mach_commands.py

@@ -0,0 +1,90 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import subprocess
+from mach.decorators import (
+    Command,
+    SubCommand,
+)
+
+# IMPORTANT: Please Request review from a DOM peer before
+# committing to using UniFFI. There are other ways to consume Rust from
+# JavaScript that might fit your use case better.
+UDL_FILES = [
+    # TODO: Use UniFFI
+]
+FIXTURE_UDL_FILES = [
+    "third_party/rust/uniffi-example-geometry/src/geometry.udl",
+    "third_party/rust/uniffi-example-arithmetic/src/arithmetic.udl",
+    "third_party/rust/uniffi-example-rondpoint/src/rondpoint.udl",
+    "third_party/rust/uniffi-example-sprites/src/sprites.udl",
+    "third_party/rust/uniffi-example-todolist/src/todolist.udl",
+]
+CPP_PATH = "toolkit/components/uniffi-js/UniFFIGeneratedScaffolding.cpp"
+JS_DIR = "toolkit/components/uniffi-bindgen-gecko-js/components/generated"
+FIXTURE_CPP_PATH = "toolkit/components/uniffi-js/UniFFIFixtureScaffolding.cpp"
+FIXTURE_JS_DIR = "toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated"
+
+
+def build_uniffi_bindgen_gecko_js(command_context):
+    uniffi_root = crate_root(command_context)
+    print("Building uniffi-bindgen-gecko-js")
+    cmdline = [
+        "cargo",
+        "build",
+        "--release",
+        "--manifest-path",
+        os.path.join(command_context.topsrcdir, "Cargo.toml"),
+        "--package",
+        "uniffi-bindgen-gecko-js",
+    ]
+    subprocess.check_call(cmdline, cwd=uniffi_root)
+    print()
+    return os.path.join(
+        command_context.topsrcdir, "target", "release", "uniffi-bindgen-gecko-js"
+    )
+
+
+@Command(
+    "uniffi",
+    category="devenv",
+    description="Generate JS bindings using uniffi-bindgen-gecko-js",
+)
+def uniffi(command_context, *runargs, **lintargs):
+    """Run uniffi."""
+    command_context._sub_mach(["help", "uniffi"])
+    return 1
+
+
+@SubCommand(
+    "uniffi",
+    "generate",
+    description="Generate/regenerate bindings",
+)
+def generate_command(command_context):
+    binary_path = build_uniffi_bindgen_gecko_js(command_context)
+    cmdline = [
+        binary_path,
+        "--js-dir",
+        JS_DIR,
+        "--fixture-js-dir",
+        FIXTURE_JS_DIR,
+        "--cpp-path",
+        CPP_PATH,
+        "--fixture-cpp-path",
+        FIXTURE_CPP_PATH,
+    ]
+    if UDL_FILES:
+        cmdline += ["--udl-files"] + UDL_FILES
+    if FIXTURE_UDL_FILES:
+        cmdline += ["--fixture-udl-files"] + FIXTURE_UDL_FILES
+    subprocess.check_call(cmdline, cwd=command_context.topsrcdir)
+    return 0
+
+
+def crate_root(command_context):
+    return os.path.join(
+        command_context.topsrcdir, "toolkit", "components", "uniffi-bindgen-gecko-js"
+    )

toolkit/components/uniffi-js/moz.build

@@ -14,6 +14,7 @@ UNIFIED_SOURCES += [
 ]
 
 if CONFIG["MOZ_UNIFFI_FIXTURES"]:
+    DEFINES["MOZ_UNIFFI_FIXTURES"] = True
     UNIFIED_SOURCES += [
         "UniFFIFixtureScaffolding.cpp",
     ]

toolkit/moz.configure

@@ -3212,7 +3212,6 @@ option(
     help="Enable UniFFI Fixtures/Examples",
 )
 
-
 set_config("MOZ_UNIFFI_FIXTURES", True, when="--enable-uniffi-fixtures")
 
 # Checks for library functions

tools/rewriting/Generated.txt

@@ -11,3 +11,4 @@ intl/unicharutil/util/nsSpecialCasingData.cpp
 intl/unicharutil/util/nsUnicodePropertyData.cpp
 toolkit/components/uniffi-js/UniFFIGeneratedScaffolding.cpp
 toolkit/components/uniffi-js/UniFFIFixtureScaffolding.cpp
+toolkit/components/uniffi-bindgen-gecko-js/fixtures/generated