Bug 1618011 part 9. Make error reporting for unions nicer. r=peterv

Instead of something like
"ByteStringSequenceSequenceOrByteStringByteStringRecord" we should have
"(sequence<sequence<ByteString>> or record<ByteString, Bytestring>)" in error
messages.

Please take a careful look at the resulting error messages (see attachment
in the bug) to see whether this makes sense.

Differential Revision: https://phabricator.services.mozilla.com/D64890

--HG--
extra : moz-landing-system : lando

dom/bindings/Codegen.py

@@ -5357,7 +5357,7 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             unionArgumentObj += ".SetValue()" if isOwningUnion else ".ref()"
 
         memberTypes = type.flatMemberTypes
-        names = []
+        prettyNames = []
 
         interfaceMemberTypes = filter(lambda t: t.isNonCallbackInterface(), memberTypes)
         if len(interfaceMemberTypes) > 0:
@@ -5367,7 +5367,7 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
                 interfaceObject.append(
                     CGGeneric("(failed = !%s.TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext" %
                               (unionArgumentObj, name)))
-                names.append(name)
+                prettyNames.append(memberType.prettyName())
             interfaceObject = CGWrapper(CGList(interfaceObject, " ||\n"),
                                         pre="done = ", post=";\n\n", reindent=True)
         else:
@@ -5376,11 +5376,12 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
         sequenceObjectMemberTypes = filter(lambda t: t.isSequence(), memberTypes)
         if len(sequenceObjectMemberTypes) > 0:
             assert len(sequenceObjectMemberTypes) == 1
-            name = getUnionMemberName(sequenceObjectMemberTypes[0])
+            memberType = sequenceObjectMemberTypes[0]
+            name = getUnionMemberName(memberType)
             sequenceObject = CGGeneric(
                 "done = (failed = !%s.TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n" %
                 (unionArgumentObj, name))
-            names.append(name)
+            prettyNames.append(memberType.prettyName())
         else:
             sequenceObject = None
 
@@ -5392,29 +5393,31 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             callbackObject = CGGeneric(
                 "done = (failed = !%s.TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n" %
                 (unionArgumentObj, name))
-            names.append(name)
+            prettyNames.append(memberType.prettyName())
         else:
             callbackObject = None
 
         dictionaryMemberTypes = filter(lambda t: t.isDictionary(), memberTypes)
         if len(dictionaryMemberTypes) > 0:
             assert len(dictionaryMemberTypes) == 1
-            name = getUnionMemberName(dictionaryMemberTypes[0])
+            memberType = dictionaryMemberTypes[0]
+            name = getUnionMemberName(memberType)
             setDictionary = CGGeneric(
                 "done = (failed = !%s.TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n" %
                 (unionArgumentObj, name))
-            names.append(name)
+            prettyNames.append(memberType.prettyName())
         else:
             setDictionary = None
 
         recordMemberTypes = filter(lambda t: t.isRecord(), memberTypes)
         if len(recordMemberTypes) > 0:
             assert len(recordMemberTypes) == 1
-            name = getUnionMemberName(recordMemberTypes[0])
+            memberType = recordMemberTypes[0]
+            name = getUnionMemberName(memberType)
             recordObject = CGGeneric(
                 "done = (failed = !%s.TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n" %
                 (unionArgumentObj, name))
-            names.append(name)
+            prettyNames.append(memberType.prettyName())
         else:
             recordObject = None
 
@@ -5428,7 +5431,7 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
                                "%s"
                                "}\n"
                                "done = true;\n" % (unionArgumentObj, indent(exceptionCode)))
-            names.append(objectMemberTypes[0].name)
+            prettyNames.append(objectMemberTypes[0].prettyName())
         else:
             object = None
 
@@ -5527,7 +5530,7 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             """,
             exceptionCode=exceptionCode,
             desc=firstCap(sourceDescription),
-            names=", ".join(names)))
+            names=", ".join(prettyNames)))
 
         templateBody = CGWrapper(CGIndenter(CGList([templateBody, throw])), pre="{\n", post="}\n")
 
@@ -5652,7 +5655,7 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
                 CGGeneric("return false;\n"),
                 ('!%s.RawSetAs%s(%s).Init(cx, JS::NullHandleValue, "Member of %s")'
                  % (declLoc, getUnionMemberName(defaultValue.type),
-                    ctorArgs, type)))
+                    ctorArgs, type.prettyName())))
             templateBody = CGIfElseWrapper("!(${haveValue})",
                                            initDictionaryWithNull,
                                            templateBody)
@@ -10566,7 +10569,8 @@ def getUnionTypeTemplateVars(unionType, type, descriptorProvider,
                    "tryNext = true;\n"
                    "return true;\n" % (prefix, name))
 
-    sourceDescription = "member of %s" % unionType
+    sourceDescription = ("%s branch of %s" %
+                         (type.prettyName(), unionType.prettyName()))
 
     conversionInfo = getJSToNativeConversionInfo(
         type, descriptorProvider, failureCode=tryNextCode,

dom/bindings/parser/WebIDL.py

@@ -2122,6 +2122,14 @@ class IDLType(IDLObject):
     def __str__(self):
         return str(self.name)
 
+    def prettyName(self):
+        """
+        A name that looks like what this type is named in the IDL spec.  By default
+        this is just our .name, but types that have more interesting spec
+        representations should override this.
+        """
+        return str(self.name)
+
     def isType(self):
         return True
 
@@ -2353,6 +2361,9 @@ class IDLNullableType(IDLParametrizedType):
     def __str__(self):
         return self.inner.__str__() + "OrNull"
 
+    def prettyName(self):
+        return self.inner.prettyName() + "?"
+
     def nullable(self):
         return True
 
@@ -2512,6 +2523,9 @@ class IDLSequenceType(IDLParametrizedType):
     def __str__(self):
         return self.inner.__str__() + "Sequence"
 
+    def prettyName(self):
+        return "sequence<%s>" % self.inner.prettyName()
+
     def nullable(self):
         return False
 
@@ -2593,6 +2607,9 @@ class IDLRecordType(IDLParametrizedType):
     def __str__(self):
         return self.keyType.__str__() + self.inner.__str__() + "Record"
 
+    def prettyName(self):
+        return "record<%s, %s>" % (self.keyType.prettyName(), self.inner.prettyName())
+
     def isRecord(self):
         return True
 
@@ -2642,6 +2659,9 @@ class IDLUnionType(IDLType):
         assert self.isComplete()
         return self.name.__hash__()
 
+    def prettyName(self):
+        return "(" + " or ".join(m.prettyName() for m in self.memberTypes) + ")"
+
     def isVoid(self):
         return False
 
@@ -3078,6 +3098,9 @@ class IDLPromiseType(IDLParametrizedType):
     def __str__(self):
         return self.inner.__str__() + "Promise"
 
+    def prettyName(self):
+        return "Promise<%s>" % self.inner.prettyName()
+
     def isPromise(self):
         return True
 
@@ -3185,6 +3208,42 @@ class IDLBuiltinType(IDLType):
         Types.ReadableStream: IDLType.Tags.interface,
     }
 
+    PrettyNames = {
+        Types.byte: "byte",
+        Types.octet: "octet",
+        Types.short: "short",
+        Types.unsigned_short: "unsigned short",
+        Types.long: "long",
+        Types.unsigned_long: "unsigned long",
+        Types.long_long: "long long",
+        Types.unsigned_long_long: "unsigned long long",
+        Types.boolean: "boolean",
+        Types.unrestricted_float: "unrestricted float",
+        Types.float: "float",
+        Types.unrestricted_double: "unrestricted double",
+        Types.double: "double",
+        Types.any: "any",
+        Types.domstring: "DOMString",
+        Types.bytestring: "ByteString",
+        Types.usvstring: "USVString",
+        Types.utf8string: "USVString", # That's what it is in spec terms
+        Types.jsstring: "USVString", # Again, that's what it is in spec terms
+        Types.object: "object",
+        Types.void: "void",
+        Types.ArrayBuffer: "ArrayBuffer",
+        Types.ArrayBufferView: "ArrayBufferView",
+        Types.Int8Array: "Int8Array",
+        Types.Uint8Array: "Uint8Array",
+        Types.Uint8ClampedArray: "Uint8ClampedArray",
+        Types.Int16Array: "Int16Array",
+        Types.Uint16Array: "Uint16Array",
+        Types.Int32Array: "Int32Array",
+        Types.Uint32Array: "Uint32Array",
+        Types.Float32Array: "Float32Array",
+        Types.Float64Array: "Float64Array",
+        Types.ReadableStream: "ReadableStream",
+    }
+
     def __init__(self, location, name, type, clamp=False, enforceRange=False, treatNullAsEmpty=False,
                  allowShared=False, attrLocation=[]):
         """
@@ -3232,6 +3291,9 @@ class IDLBuiltinType(IDLType):
             return "MaybeShared" + str(self.name)
         return str(self.name)
 
+    def prettyName(self):
+        return IDLBuiltinType.PrettyNames[self._typeTag]
+
     def clamped(self, attrLocation):
         if not self._clamped:
             self._clamped = IDLBuiltinType(self.location, self.name,