Auto merge of #12790 - malisas:malisa-bytestring-generator, r=Ms2ger

Update bindings generator to support default ByteString values in a dictionary

<!-- Please describe your changes on the following line: -->
Update bindings generator to support default ByteString values in a dictionary.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12737 (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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2 files changed, 27 insertions, 3 deletions

diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 2e0dc2415dd..8a288694431 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -866,11 +866,22 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             "    Err(_) => { %s },\n"
             "}" % exceptionCode)
 
-        declType = CGGeneric("ByteString")
+        if defaultValue is None:
+            default = None
+        elif isinstance(defaultValue, IDLNullValue):
+            assert type.nullable()
+            default = "None"
+        else:
+            assert defaultValue.type.tag() in (IDLType.Tags.domstring, IDLType.Tags.bytestring)
+            default = 'ByteString::new(b"%s".to_vec())' % defaultValue.value
+            if type.nullable():
+                default = "Some(%s)" % default
+
+        declType = "ByteString"
         if type.nullable():
-            declType = CGWrapper(declType, pre="Option<", post=">")
+            declType = "Option<%s>" % declType
 
-        return handleOptional(conversionCode, declType, handleDefaultNull("None"))
+        return handleOptional(conversionCode, CGGeneric(declType), default)
 
     if type.isEnum():
         assert not isEnforceRange and not isClamp
diff --git a/components/script/dom/bindings/codegen/parser/WebIDL.py b/components/script/dom/bindings/codegen/parser/WebIDL.py
index da32340dda6..54d510781a1 100644
--- a/components/script/dom/bindings/codegen/parser/WebIDL.py
+++ b/components/script/dom/bindings/codegen/parser/WebIDL.py
@@ -3391,6 +3391,11 @@ class IDLValue(IDLObject):
             # extra normalization step.
             assert self.type.isDOMString()
             return self
+        elif self.type.isString() and type.isByteString():
+            # Allow ByteStrings to use default value just like
+            # DOMString.  No coercion is required here.
+            assert self.type.isDOMString()
+            return self
         raise WebIDLError("Cannot coerce type %s to type %s." %
                           (self.type, type), [location])
 
@@ -5759,6 +5764,14 @@ class Parser(Tokenizer):
         booleanType = BuiltinTypes[IDLBuiltinType.Types.boolean]
         p[0] = IDLValue(location, booleanType, p[1])
 
+    def p_ConstValueByteString(self, p):
+        """
+            ConstValue : BYTESTRING
+        """
+        location = self.getLocation(p, 1)
+        bytestringType = BuiltinTypes[IDLBuiltinType.Types.bytestring]
+        p[0] = IDLValue(location, bytestringType, p[1])
+
     def p_ConstValueInteger(self, p):
         """
             ConstValue : INTEGER