Bug 835417 part 2. Implement WebIDL parser and codegen support for marking things pure. r=peterv

dom/bindings/Codegen.py

@@ -4547,11 +4547,13 @@ class CGMemberJITInfo(CGThing):
         return ""
 
     def defineJitInfo(self, infoName, opName, opType, infallible, constant,
-                      returnTypes):
+                      pure, returnTypes):
+        assert(not constant or pure) # constants are always pure
         protoID = "prototypes::id::%s" % self.descriptor.name
         depth = "PrototypeTraits<%s>::Depth" % protoID
         failstr = toStringBool(infallible)
         conststr = toStringBool(constant)
+        purestr = toStringBool(pure)
         returnType = reduce(CGMemberJITInfo.getSingleReturnType, returnTypes,
                             "")
         return ("\n"
@@ -4562,26 +4564,30 @@ class CGMemberJITInfo(CGThing):
                 "  JSJitInfo::%s,\n"
                 "  %s,  /* isInfallible. False in setters. */\n"
                 "  %s,  /* isConstant. Only relevant for getters. */\n"
+                "  %s,  /* isPure.  Only relevant for getters. */\n"
                 "  %s   /* returnType.  Only relevant for getters/methods. */\n"
                 "};\n" % (infoName, opName, protoID, depth, opType, failstr,
-                          conststr, returnType))
+                          conststr, purestr, returnType))
 
     def define(self):
         if self.member.isAttr():
             getterinfo = ("%s_getterinfo" % self.member.identifier.name)
             getter = ("(JSJitPropertyOp)get_%s" % self.member.identifier.name)
             getterinfal = "infallible" in self.descriptor.getExtendedAttributes(self.member, getter=True)
-            getterinfal = getterinfal and infallibleForMember(self.member, self.member.type, self.descriptor)
             getterconst = self.member.getExtendedAttribute("Constant")
+            getterpure = getterconst or self.member.getExtendedAttribute("Pure")
+            assert (getterinfal or (not getterconst and not getterpure))
+
+            getterinfal = getterinfal and infallibleForMember(self.member, self.member.type, self.descriptor)
             result = self.defineJitInfo(getterinfo, getter, "Getter",
-                                        getterinfal, getterconst,
+                                        getterinfal, getterconst, getterpure,
                                         [self.member.type])
             if not self.member.readonly or self.member.getExtendedAttribute("PutForwards") is not None:
                 setterinfo = ("%s_setterinfo" % self.member.identifier.name)
                 setter = ("(JSJitPropertyOp)set_%s" % self.member.identifier.name)
                 # Setters are always fallible, since they have to do a typed unwrap.
                 result += self.defineJitInfo(setterinfo, setter, "Setter",
-                                             False, False,
+                                             False, False, False,
                                              [BuiltinTypes[IDLBuiltinType.Types.void]])
             return result
         if self.member.isMethod():
@@ -4593,18 +4599,22 @@ class CGMemberJITInfo(CGThing):
             # Methods are infallible if they are infallible, have no arguments
             # to unwrap, and have a return type that's infallible to wrap up for
             # return.
-            methodInfal = False
             sigs = self.member.signatures()
-            if len(sigs) == 1:
-                # Don't handle overloading. If there's more than one signature,
+            if len(sigs) != 1:
+                # Don't handle overloading.  If there's more than one signature,
                 # one of them must take arguments.
+                methodInfal = False
+            else:
                 sig = sigs[0]
-                if len(sig[1]) == 0 and infallibleForMember(self.member, sig[0], self.descriptor):
-                    # No arguments and infallible return boxing
-                    methodInfal = True
+                if (len(sig[1]) != 0 or
+                    not infallibleForMember(self.member, sig[0], self.descriptor)):
+                    # We have arguments or our return-value boxing can fail
+                    methodInfal = False
+                else:
+                    methodInfal = "infallible" in self.descriptor.getExtendedAttributes(self.member)
 
             result = self.defineJitInfo(methodinfo, method, "Method",
-                                        methodInfal, False,
+                                        methodInfal, False, False,
                                         [s[0] for s in sigs])
             return result
         raise TypeError("Illegal member type to CGPropertyJITInfo")

dom/bindings/parser/WebIDL.py

@@ -2194,6 +2194,14 @@ class IDLAttribute(IDLInterfaceMember):
             raise WebIDLError("Readonly attributes must not be flagged as "
                               "[SetterThrows]",
                               [self.location])
+        elif (((identifier == "Throws" or identifier == "GetterThrows") and
+               (self.getExtendedAttribute("Pure") or
+                self.getExtendedAttribute("Constant"))) or
+              ((identifier == "Pure" or identifier == "Constant") and
+               (self.getExtendedAttribute("Throws") or
+                self.getExtendedAttribute("GetterThrows")))):
+            raise WebIDLError("Throwing things can't be [Pure] or [Constant]",
+                              [attr.location])
         elif identifier == "LenientThis":
             if not attr.noArguments():
                 raise WebIDLError("[LenientThis] must take no arguments",
@@ -2736,8 +2744,11 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
                               "[Unforgeable]",
                               [attr.location, self.location])
         elif identifier == "Constant":
-            raise WebIDLError("Methods must not be flagged as "
-                              "[Constant]",
+            raise WebIDLError("Methods must not be flagged as [Constant]",
+                              [attr.location, self.location]);
+        elif identifier == "Pure":
+            raise WebIDLError("Methods must not be flagged as [Pure] and if "
+                              "that changes, don't forget to check for [Throws]",
                               [attr.location, self.location]);
         elif identifier == "PutForwards":
             raise WebIDLError("Only attributes support [PutForwards]",

dom/webidl/Document.webidl

@@ -31,7 +31,7 @@ enum VisibilityState { "hidden", "visible" };
 /* http://dom.spec.whatwg.org/#interface-document */
 [Constructor]
 interface Document : Node {
-  [Throws, Constant]
+  [Throws]
   readonly attribute DOMImplementation implementation;
   readonly attribute DOMString URL;
   readonly attribute DOMString documentURI;

js/src/jsfriendapi.h

@@ -1263,6 +1263,9 @@ struct JSJitInfo {
     OpType type;
     bool isInfallible;      /* Is op fallible? False in setters. */
     bool isConstant;        /* Getting a construction-time constant? */
+    bool isPure;            /* As long as no non-pure DOM things happen, will
+                               keep returning the same value for the given
+                               "this" object" */
     JSValueType returnType; /* The return type tag.  Might be JSVAL_TYPE_UNKNOWN */
 };