From 16db1fc4c05d3f863abeb1bc54f94077576f41ed Mon Sep 17 00:00:00 2001
From: Boris Zbarsky <bzbarsky@mit.edu>
Date: Fri, 5 Sep 2014 14:28:43 -0400
Subject: [PATCH] Bug 1057541 part 2.  Add a way to ask an IDLArgument whether
 it guarantees that it will always have a value.  r=khuey

---
 dom/bindings/Codegen.py       | 26 +++++++++++++-------------
 dom/bindings/parser/WebIDL.py |  3 +++
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/dom/bindings/Codegen.py b/dom/bindings/Codegen.py
index 7bf5e5388ab8..f368b858e0a5 100644
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -5287,7 +5287,7 @@ class CGArgumentConverter(CGThing):
             "args.hasDefined(${index})").substitute(replacer)
         self.replacementVariables["haveValue"] = haveValueCheck
         self.descriptorProvider = descriptorProvider
-        if self.argument.optional and not self.argument.defaultValue:
+        if self.argument.canHaveMissingValue():
             self.argcAndIndex = replacer
         else:
             self.argcAndIndex = None
@@ -6130,10 +6130,9 @@ class CGCallGenerator(CGThing):
                     return True
                 if a.type.isString():
                     return True
-                if a.optional and not a.defaultValue:
-                    # If a.defaultValue, then it's not going to use an Optional,
-                    # so doesn't need to be const just due to being optional.
-                    # This also covers variadic arguments.
+                if a.canHaveMissingValue():
+                    # This will need an Optional or it's a variadic;
+                    # in both cases it should be const.
                     return True
                 if a.type.isUnion():
                     return True
@@ -6350,7 +6349,7 @@ def wrapArgIntoCurrentCompartment(arg, value, isMember=True):
     As wrapTypeIntoCurrentCompartment but handles things being optional
     """
     origValue = value
-    isOptional = arg.optional and not arg.defaultValue
+    isOptional = arg.canHaveMissingValue()
     if isOptional:
         value = value + ".Value()"
     wrap = wrapTypeIntoCurrentCompartment(arg.type, value, isMember)
@@ -6857,8 +6856,7 @@ class CGMethodCall(CGThing):
                 # enough that we can examine this argument.  But note that we
                 # still want to claim that optional arguments are optional, in
                 # case undefined was passed in.
-                argIsOptional = (distinguishingArgument(signature).optional and
-                                 not distinguishingArgument(signature).defaultValue)
+                argIsOptional = distinguishingArgument(signature).canHaveMissingValue()
                 testCode = instantiateJSToNativeConversion(
                     getJSToNativeConversionInfo(type, descriptor,
                                                 failureCode=failureCode,
@@ -7144,6 +7142,9 @@ class FakeArgument():
     def allowTreatNonCallableAsNull(self):
         return self._allowTreatNonCallableAsNull
 
+    def canHaveMissingValue(self):
+        return False
+
 
 class CGSetterCall(CGPerSignatureCall):
     """
@@ -12526,8 +12527,7 @@ class CGNativeMember(ClassMethod):
         """
         Get the full argument declaration for an argument
         """
-        decl, ref = self.getArgType(arg.type,
-                                    arg.optional and not arg.defaultValue,
+        decl, ref = self.getArgType(arg.type, arg.canHaveMissingValue(),
                                     "Variadic" if arg.variadic else False)
         if ref:
             decl = CGWrapper(decl, pre="const ", post="&")
@@ -13606,7 +13606,7 @@ class CallbackMember(CGNativeMember):
             jsvalIndex = "%d + idx" % i
         else:
             jsvalIndex = "%d" % i
-            if arg.optional and not arg.defaultValue:
+            if arg.canHaveMissingValue():
                 argval += ".Value()"
         if arg.type.isDOMString():
             # XPConnect string-to-JS conversion wants to mutate the string.  So
@@ -13649,7 +13649,7 @@ class CallbackMember(CGNativeMember):
                 """,
                 arg=arg.identifier.name,
                 conversion=conversion)
-        elif arg.optional and not arg.defaultValue:
+        elif arg.canHaveMissingValue():
             conversion = fill(
                 """
                 if (${argName}.WasPassed()) {
@@ -14383,7 +14383,7 @@ class CGEventMethod(CGNativeMember):
 
     def getArg(self, arg):
         decl, ref = self.getArgType(arg.type,
-                                    arg.optional and not arg.defaultValue,
+                                    arg.canHaveMissingValue(),
                                     "Variadic" if arg.variadic else False)
         if ref:
             decl = CGWrapper(decl, pre="const ", post="&")
diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index 77169683d249..4e16de86de0d 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -3474,6 +3474,9 @@ class IDLArgument(IDLObjectWithIdentifier):
             deps.add(self.defaultValue)
         return deps
 
+    def canHaveMissingValue(self):
+        return self.optional and not self.defaultValue
+
 class IDLCallbackType(IDLType, IDLObjectWithScope):
     def __init__(self, location, parentScope, identifier, returnType, arguments):
         assert isinstance(returnType, IDLType)