Bug 1703089 - Implement WebAssembly.Exception constructor r=rhunt

Differential Revision: https://phabricator.services.mozilla.com/D110851

js/public/friend/ErrorNumbers.msg

@@ -465,6 +465,9 @@ MSG_DEF(JSMSG_WASM_BAD_EQREF_VALUE,  0, JSEXN_TYPEERR,     "can only pass a Type
 MSG_DEF(JSMSG_WASM_BAD_VAL_TYPE,       0, JSEXN_TYPEERR,     "cannot pass v128 to or from JS")
 MSG_DEF(JSMSG_WASM_BAD_STRING_VAL_TYPE,    0, JSEXN_TYPEERR,     "bad value type")
 MSG_DEF(JSMSG_WASM_BAD_STRING_IDX_TYPE,    0, JSEXN_TYPEERR,     "bad index type")
+MSG_DEF(JSMSG_WASM_BAD_EXN_ARG,        0, JSEXN_TYPEERR,     "first argument must be a WebAssembly.Tag")
+MSG_DEF(JSMSG_WASM_BAD_EXN_PAYLOAD,    0, JSEXN_TYPEERR,     "second argument must be an object")
+MSG_DEF(JSMSG_WASM_BAD_EXN_PAYLOAD_LEN, 2, JSEXN_TYPEERR,    "expected {0} values but got {1}")
 MSG_DEF(JSMSG_WASM_NO_TRANSFER,        0, JSEXN_TYPEERR,     "cannot transfer WebAssembly/asm.js ArrayBuffer")
 MSG_DEF(JSMSG_WASM_TEXT_FAIL,          1, JSEXN_SYNTAXERR,   "wasm text error: {0}")
 MSG_DEF(JSMSG_WASM_MISSING_MAXIMUM,    0, JSEXN_TYPEERR,     "'shared' is true but maximum is not specified")

js/src/jit-test/tests/wasm/exceptions/import-export.js

@@ -8,12 +8,6 @@ function testException() {
     WebAssembly.RuntimeError,
     /cannot call WebAssembly.Tag/
   );
-
-  assertErrorMessage(
-    () => new WebAssembly.Exception(),
-    WebAssembly.RuntimeError,
-    /cannot call WebAssembly.Exception/
-  );
 }
 
 function testImports() {

js/src/jit-test/tests/wasm/exceptions/js-api.js

@@ -0,0 +1,173 @@
+// Tests for wasm exception proposal JS API features.
+
+load(libdir + "eqArrayHelper.js");
+
+assertErrorMessage(
+  () => WebAssembly.Exception(),
+  TypeError,
+  /calling a builtin Exception constructor without new is forbidden/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(),
+  TypeError,
+  /At least 2 arguments required/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(3, []),
+  TypeError,
+  /first argument must be a WebAssembly.Tag/
+);
+
+const { tag1, tag2, tag3, tag4, tag5, tag6, tag7 } = wasmEvalText(
+  `(module
+     (event (export "tag1") (param))
+     (event (export "tag2") (param i32))
+     (event (export "tag3") (param i32 f32))
+     (event (export "tag4") (param i32 externref i32))
+     (event (export "tag5") (param i32 externref i32 externref))
+     (event (export "tag6") (param funcref))
+     (event (export "tag7") (param i64)))`
+).exports;
+
+new WebAssembly.Exception(tag1, []);
+new WebAssembly.Exception(tag2, [3]);
+new WebAssembly.Exception(tag3, [3, 5.5]);
+new WebAssembly.Exception(tag4, [3, "foo", 4]);
+new WebAssembly.Exception(tag5, [3, "foo", 4, "bar"]);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(tag2, []),
+  TypeError,
+  /expected 1 values but got 0/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(tag2, [3n]),
+  TypeError,
+  /can't convert BigInt to number/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(tag6, [undefined]),
+  TypeError,
+  /can only pass WebAssembly exported functions to funcref/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(tag7, [undefined]),
+  TypeError,
+  /can't convert undefined to BigInt/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(tag7, {}),
+  TypeError,
+  /\({}\) is not iterable/
+);
+
+assertErrorMessage(
+  () => new WebAssembly.Exception(tag7, 1),
+  TypeError,
+  /second argument must be an object/
+);
+
+// Test throwing a JS constructed exception to Wasm.
+assertEq(
+  wasmEvalText(
+    `(module
+       (import "m" "exn" (event $exn (param i32)))
+       (import "m" "f" (func $f))
+       (func (export "f") (result i32)
+         try (result i32)
+           call $f
+           (i32.const 0)
+         catch $exn
+         end))`,
+    {
+      m: {
+        exn: tag2,
+        f: () => {
+          throw new WebAssembly.Exception(tag2, [42]);
+        },
+      },
+    }
+  ).exports.f(),
+  42
+);
+
+assertEqArray(
+  wasmEvalText(
+    `(module
+       (import "m" "exn" (event $exn (param i32 f32)))
+       (import "m" "f" (func $f))
+       (func (export "f") (result i32 f32)
+         try (result i32 f32)
+           call $f
+           (i32.const 0)
+           (f32.const 0)
+         catch $exn
+         end))`,
+    {
+      m: {
+        exn: tag3,
+        f: () => {
+          throw new WebAssembly.Exception(tag3, [42, 5.5]);
+        },
+      },
+    }
+  ).exports.f(),
+  [42, 5.5]
+);
+
+assertEqArray(
+  wasmEvalText(
+    `(module
+       (import "m" "exn" (event $exn (param i32 externref i32)))
+       (import "m" "f" (func $f))
+       (func (export "f") (result i32 externref i32)
+         try (result i32 externref i32)
+           call $f
+           (i32.const 0)
+           (ref.null extern)
+           (i32.const 0)
+         catch $exn
+         end))`,
+    {
+      m: {
+        exn: tag4,
+        f: () => {
+          throw new WebAssembly.Exception(tag4, [42, "foo", 42]);
+        },
+      },
+    }
+  ).exports.f(),
+  [42, "foo", 42]
+);
+
+assertEq(
+  wasmEvalText(
+    `(module
+       (import "m" "exn" (event $exn))
+       (import "m" "f" (func $f))
+       (func (export "f") (result i32)
+         try (result i32)
+           call $f
+           (i32.const 0)
+         catch $exn
+           (i32.const 0)
+         catch_all
+           (i32.const 1)
+         end))`,
+    {
+      m: {
+        exn: tag1,
+        f: () => {
+          throw new WebAssembly.Exception(tag2, [42]);
+        },
+      },
+    }
+  ).exports.f(),
+  1
+);

js/src/wasm/WasmJS.cpp

@@ -3584,6 +3584,8 @@ void WasmTagObject::finalize(JSFreeOp* fop, JSObject* obj) {
   }
 }
 
+static bool IsTagObject(JSObject* obj) { return obj->is<WasmTagObject>(); }
+
 bool WasmTagObject::construct(JSContext* cx, unsigned argc, Value* vp) {
   CallArgs args = CallArgsFromVp(argc, vp);
 
@@ -3710,14 +3712,90 @@ bool WasmExceptionObject::construct(JSContext* cx, unsigned argc, Value* vp) {
     return false;
   }
 
-  // FIXME: When the JS API is finalized, it may be possible to construct
-  // WebAssembly.Exception instances from JS, but not for now.
-  JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
-                           JSMSG_WASM_EXN_CONSTRUCTOR, "WebAssembly.Exception");
-
+  if (!args.requireAtLeast(cx, "WebAssembly.Exception", 2)) {
     return false;
   }
 
+  if (!args[0].isObject() || !IsTagObject(&args[0].toObject())) {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                             JSMSG_WASM_BAD_EXN_ARG);
+    return false;
+  }
+
+  RootedWasmTagObject exnTag(cx, &args[0].toObject().as<WasmTagObject>());
+
+  if (!args.get(1).isObject()) {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                             JSMSG_WASM_BAD_EXN_PAYLOAD);
+    return false;
+  }
+
+  JS::ForOfIterator iterator(cx);
+  if (!iterator.init(args.get(1), JS::ForOfIterator::ThrowOnNonIterable)) {
+    return false;
+  }
+
+  wasm::ValTypeVector& params = exnTag->valueTypes();
+
+  // This is pre-sizing the data buffer for the exception object.
+  size_t nbytes = 0;
+  for (const ValType param : params) {
+    if (!param.isReference()) {
+      nbytes += SizeOf(param);
+    }
+  }
+
+  RootedArrayBufferObject buf(cx, ArrayBufferObject::createZeroed(cx, nbytes));
+  if (!buf) {
+    return false;
+  }
+
+  RootedArrayObject refs(cx, NewDenseEmptyArray(cx));
+  if (!refs) {
+    return false;
+  }
+
+  uint8_t* bufPtr = buf->dataPointer();
+  RootedValue nextArg(cx);
+  for (size_t i = 0; i < params.length(); i++) {
+    bool done;
+    if (!iterator.next(&nextArg, &done)) {
+      return false;
+    }
+    if (done) {
+      UniqueChars expected(JS_smprintf("%zu", params.length()));
+      UniqueChars got(JS_smprintf("%zu", i));
+
+      JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                               JSMSG_WASM_BAD_EXN_PAYLOAD_LEN, expected.get(),
+                               got.get());
+      return false;
+    }
+
+    if (params[i].isReference()) {
+      RootedObject objPtr(cx);
+      if (!ToWebAssemblyValue(cx, nextArg, params[i], objPtr.address(), true)) {
+        return false;
+      }
+      if (!NewbornArrayPush(cx, refs, ObjectValue(*objPtr))) {
+        return false;
+      }
+    } else {
+      if (!ToWebAssemblyValue(cx, nextArg, params[i], bufPtr, true)) {
+        return false;
+      }
+      bufPtr += SizeOf(params[i]);
+    }
+  }
+
+  RootedWasmExceptionObject exnObj(
+      cx, WasmExceptionObject::create(cx, SharedExceptionTag(&exnTag->tag()),
+                                      buf, refs));
+
+  args.rval().setObject(*exnObj);
+  return true;
+}
+
 /* static */
 WasmExceptionObject* WasmExceptionObject::create(JSContext* cx,
                                                  wasm::SharedExceptionTag tag,