dom/bindings/Configuration.py
author Edgar Chen <echen@mozilla.com>
Mon, 27 Nov 2017 16:10:27 +0800
changeset 450522 57a108d1c90a9979e2b79dbf138e055ee07ed97b
parent 449479 03636aaf6cd729bc13d2ed6877e597ef7d226dcf
child 451371 da3dec2fce062bc6c7756d9df6e893f827356b14
permissions -rw-r--r--
Bug 1422197 - Add fast path to get DocGroup in binding code for [CEReactions]; r=smaug MozReview-Commit-ID: HgbFo9ddr0o

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.

from WebIDL import IDLImplementsStatement
import os
from collections import defaultdict

autogenerated_comment = "/* THIS FILE IS AUTOGENERATED - DO NOT EDIT */\n"


class DescriptorProvider:
    """
    A way of getting descriptors for interface names.  Subclasses must
    have a getDescriptor method callable with the interface name only.
    """
    def __init__(self):
        pass


class Configuration(DescriptorProvider):
    """
    Represents global configuration state based on IDL parse data and
    the configuration file.
    """
    def __init__(self, filename, parseData, generatedEvents=[]):
        DescriptorProvider.__init__(self)

        # Read the configuration file.
        glbl = {}
        execfile(filename, glbl)
        config = glbl['DOMInterfaces']

        # Build descriptors for all the interfaces we have in the parse data.
        # This allows callers to specify a subset of interfaces by filtering
        # |parseData|.
        self.descriptors = []
        self.interfaces = {}
        self.descriptorsByName = {}
        self.optimizedOutDescriptorNames = set()
        self.generatedEvents = generatedEvents
        self.maxProtoChainLength = 0
        for thing in parseData:
            if isinstance(thing, IDLImplementsStatement):
                # Our build system doesn't support dep build involving
                # addition/removal of "implements" statements that appear in a
                # different .webidl file than their LHS interface.  Make sure we
                # don't have any of those.  See similar block below for partial
                # interfaces!
                #
                # But whitelist a RHS that is LegacyQueryInterface,
                # since people shouldn't be adding any of those.
                if (thing.implementor.filename() != thing.filename() and
                    thing.implementee.identifier.name != "LegacyQueryInterface"):
                    raise TypeError(
                        "The binding build system doesn't really support "
                        "'implements' statements which don't appear in the "
                        "file in which the left-hand side of the statement is "
                        "defined.  Don't do this unless your right-hand side "
                        "is LegacyQueryInterface.\n"
                        "%s\n"
                        "%s" %
                        (thing.location, thing.implementor.location))

            assert not thing.isType()

            if not thing.isInterface() and not thing.isNamespace():
                continue
            iface = thing
            # Our build system doesn't support dep builds involving
            # addition/removal of partial interfaces that appear in a different
            # .webidl file than the interface they are extending.  Make sure we
            # don't have any of those.  See similar block above for "implements"
            # statements!
            if not iface.isExternal():
                for partialIface in iface.getPartialInterfaces():
                    if (partialIface.filename() != iface.filename() and
                        # Unfortunately, NavigatorProperty does exactly the
                        # thing we're trying to prevent here.  I'm not sure how
                        # to deal with that, short of effectively requiring a
                        # clobber when NavigatorProperty is added/removed and
                        # whitelisting the things it outputs here as
                        # restrictively as I can.
                        (partialIface.identifier.name != "Navigator" or
                         len(partialIface.members) != 1 or
                         partialIface.members[0].location != partialIface.location or
                         partialIface.members[0].identifier.location.filename() !=
                           "<builtin>")):
                        raise TypeError(
                            "The binding build system doesn't really support "
                            "partial interfaces which don't appear in the "
                            "file in which the interface they are extending is "
                            "defined.  Don't do this.\n"
                            "%s\n"
                            "%s" %
                            (partialIface.location, iface.location))
            self.interfaces[iface.identifier.name] = iface
            if iface.identifier.name not in config:
                # Completely skip consequential interfaces with no descriptor
                # if they have no interface object because chances are we
                # don't need to do anything interesting with them.
                if iface.isConsequential() and not iface.hasInterfaceObject():
                    self.optimizedOutDescriptorNames.add(iface.identifier.name)
                    continue
                entry = {}
            else:
                entry = config[iface.identifier.name]
            assert not isinstance(entry, list)
            desc = Descriptor(self, iface, entry)
            self.descriptors.append(desc)
            # Setting up descriptorsByName while iterating through interfaces
            # means we can get the nativeType of iterable interfaces without
            # having to do multiple loops.
            assert desc.interface.identifier.name not in self.descriptorsByName
            self.descriptorsByName[desc.interface.identifier.name] = desc

        # Keep the descriptor list sorted for determinism.
        self.descriptors.sort(lambda x, y: cmp(x.name, y.name))


        self.descriptorsByFile = {}
        for d in self.descriptors:
            self.descriptorsByFile.setdefault(d.interface.filename(),
                                              []).append(d)

        self.enums = [e for e in parseData if e.isEnum()]

        self.dictionaries = [d for d in parseData if d.isDictionary()]
        self.callbacks = [c for c in parseData if
                          c.isCallback() and not c.isInterface()]

        # Dictionary mapping from a union type name to a set of filenames where
        # union types with that name are used.
        self.filenamesPerUnion = defaultdict(set)

        # Dictionary mapping from a filename to a list of types for
        # the union types used in that file. If a union type is used
        # in multiple files then it will be added to the list for the
        # None key. Note that the list contains a type for every use
        # of a union type, so there can be multiple entries with union
        # types that have the same name.
        self.unionsPerFilename = defaultdict(list)

        for (t, _) in getAllTypes(self.descriptors, self.dictionaries, self.callbacks):
            while True:
                if t.isRecord():
                    t = t.inner
                elif t.unroll() != t:
                    t = t.unroll()
                elif t.isPromise():
                    t = t.promiseInnerType()
                else:
                    break
            if t.isUnion():
                filenamesForUnion = self.filenamesPerUnion[t.name]
                if t.filename() not in filenamesForUnion:
                    # We have a to be a bit careful: some of our built-in
                    # typedefs are for unions, and those unions end up with
                    # "<unknown>" as the filename.  If that happens, we don't
                    # want to try associating this union with one particular
                    # filename, since there isn't one to associate it with,
                    # really.
                    if t.filename() == "<unknown>":
                        uniqueFilenameForUnion = None
                    elif len(filenamesForUnion) == 0:
                        # This is the first file that we found a union with this
                        # name in, record the union as part of the file.
                        uniqueFilenameForUnion = t.filename()
                    else:
                        # We already found a file that contains a union with
                        # this name.
                        if len(filenamesForUnion) == 1:
                            # This is the first time we found a union with this
                            # name in another file.
                            for f in filenamesForUnion:
                                # Filter out unions with this name from the
                                # unions for the file where we previously found
                                # them.
                                unionsForFilename = self.unionsPerFilename[f]
                                unionsForFilename = filter(lambda u: u.name != t.name,
                                                           unionsForFilename)
                                if len(unionsForFilename) == 0:
                                    del self.unionsPerFilename[f]
                                else:
                                    self.unionsPerFilename[f] = unionsForFilename
                        # Unions with this name appear in multiple files, record
                        # the filename as None, so that we can detect that.
                        uniqueFilenameForUnion = None
                    self.unionsPerFilename[uniqueFilenameForUnion].append(t)
                    filenamesForUnion.add(t.filename())

    def getInterface(self, ifname):
        return self.interfaces[ifname]

    def getDescriptors(self, **filters):
        """Gets the descriptors that match the given filters."""
        curr = self.descriptors
        # Collect up our filters, because we may have a webIDLFile filter that
        # we always want to apply first.
        tofilter = []
        for key, val in filters.iteritems():
            if key == 'webIDLFile':
                # Special-case this part to make it fast, since most of our
                # getDescriptors calls are conditioned on a webIDLFile.  We may
                # not have this key, in which case we have no descriptors
                # either.
                curr = self.descriptorsByFile.get(val, [])
                continue
            elif key == 'hasInterfaceObject':
                getter = lambda x: (not x.interface.isExternal() and
                                    x.interface.hasInterfaceObject())
            elif key == 'hasInterfacePrototypeObject':
                getter = lambda x: (not x.interface.isExternal() and
                                    x.interface.hasInterfacePrototypeObject())
            elif key == 'hasInterfaceOrInterfacePrototypeObject':
                getter = lambda x: x.hasInterfaceOrInterfacePrototypeObject()
            elif key == 'isCallback':
                getter = lambda x: x.interface.isCallback()
            elif key == 'isExternal':
                getter = lambda x: x.interface.isExternal()
            elif key == 'isJSImplemented':
                getter = lambda x: x.interface.isJSImplemented()
            elif key == 'isNavigatorProperty':
                getter = lambda x: x.interface.isNavigatorProperty()
            elif key == 'isExposedInAnyWorker':
                getter = lambda x: x.interface.isExposedInAnyWorker()
            elif key == 'isExposedInWorkerDebugger':
                getter = lambda x: x.interface.isExposedInWorkerDebugger()
            elif key == 'isExposedInAnyWorklet':
                getter = lambda x: x.interface.isExposedInAnyWorklet()
            elif key == 'isExposedInSystemGlobals':
                getter = lambda x: x.interface.isExposedInSystemGlobals()
            elif key == 'isExposedInWindow':
                getter = lambda x: x.interface.isExposedInWindow()
            else:
                # Have to watch out: just closing over "key" is not enough,
                # since we're about to mutate its value
                getter = (lambda attrName: lambda x: getattr(x, attrName))(key)
            tofilter.append((getter, val))
        for f in tofilter:
            curr = filter(lambda x: f[0](x) == f[1], curr)
        return curr

    def getEnums(self, webIDLFile):
        return filter(lambda e: e.filename() == webIDLFile, self.enums)

    def getDictionaries(self, webIDLFile):
        return filter(lambda d: d.filename() == webIDLFile, self.dictionaries)

    def getCallbacks(self, webIDLFile):
        return filter(lambda c: c.filename() == webIDLFile, self.callbacks)

    def getDescriptor(self, interfaceName):
        """
        Gets the appropriate descriptor for the given interface name.
        """
        # We may have optimized out this descriptor, but the chances of anyone
        # asking about it are then slim.  Put the check for that _after_ we've
        # done our normal lookup.  But that means we have to do our normal
        # lookup in a way that will not throw if it fails.
        d = self.descriptorsByName.get(interfaceName, None)
        if d:
            return d

        if interfaceName in self.optimizedOutDescriptorNames:
            raise NoSuchDescriptorError(
                "No descriptor for '%s', which is a mixin ([NoInterfaceObject] "
                "and a consequential interface) without an explicit "
                "Bindings.conf annotation." % interfaceName)

        raise NoSuchDescriptorError("For " + interfaceName + " found no matches")


class NoSuchDescriptorError(TypeError):
    def __init__(self, str):
        TypeError.__init__(self, str)


def methodReturnsJSObject(method):
    assert method.isMethod()
    if method.returnsPromise():
        return True

    for signature in method.signatures():
        returnType = signature[0]
        if returnType.isObject() or returnType.isSpiderMonkeyInterface():
            return True

    return False


def MemberIsUnforgeable(member, descriptor):
    # Note: "or" and "and" return either their LHS or RHS, not
    # necessarily booleans.  Make sure to return a boolean from this
    # method, because callers will compare its return value to
    # booleans.
    return bool((member.isAttr() or member.isMethod()) and
                not member.isStatic() and
                (member.isUnforgeable() or
                 descriptor.interface.getExtendedAttribute("Unforgeable")))


class Descriptor(DescriptorProvider):
    """
    Represents a single descriptor for an interface. See Bindings.conf.
    """
    def __init__(self, config, interface, desc):
        DescriptorProvider.__init__(self)
        self.config = config
        self.interface = interface

        self.wantsXrays = (not interface.isExternal() and
                           interface.isExposedInWindow())

        if self.wantsXrays:
            # We could try to restrict self.wantsXrayExpandoClass further.  For
            # example, we could set it to false if all of our slots store
            # Gecko-interface-typed things, because we don't use Xray expando
            # slots for those.  But note that we would need to check the types
            # of not only the members of "interface" but also of all its
            # ancestors, because those can have members living in our slots too.
            # For now, do the simple thing.
            self.wantsXrayExpandoClass = (interface.totalMembersInSlots != 0)

        # Read the desc, and fill in the relevant defaults.
        ifaceName = self.interface.identifier.name
        # For generated iterator interfaces for other iterable interfaces, we
        # just use IterableIterator as the native type, templated on the
        # nativeType of the iterable interface. That way we can have a
        # templated implementation for all the duplicated iterator
        # functionality.
        if self.interface.isIteratorInterface():
            itrName = self.interface.iterableInterface.identifier.name
            itrDesc = self.getDescriptor(itrName)
            nativeTypeDefault = iteratorNativeType(itrDesc)

        elif self.interface.isExternal():
            nativeTypeDefault = "nsIDOM" + ifaceName
        else:
            nativeTypeDefault = "mozilla::dom::" + ifaceName

        self.nativeType = desc.get('nativeType', nativeTypeDefault)
        # Now create a version of nativeType that doesn't have extra
        # mozilla::dom:: at the beginning.
        prettyNativeType = self.nativeType.split("::")
        if prettyNativeType[0] == "mozilla":
            prettyNativeType.pop(0)
            if prettyNativeType[0] == "dom":
                prettyNativeType.pop(0)
        self.prettyNativeType = "::".join(prettyNativeType)

        self.jsImplParent = desc.get('jsImplParent', self.nativeType)

        # Do something sane for JSObject
        if self.nativeType == "JSObject":
            headerDefault = "js/TypeDecls.h"
        elif self.interface.isCallback() or self.interface.isJSImplemented():
            # A copy of CGHeaders.getDeclarationFilename; we can't
            # import it here, sadly.
            # Use our local version of the header, not the exported one, so that
            # test bindings, which don't export, will work correctly.
            basename = os.path.basename(self.interface.filename())
            headerDefault = basename.replace('.webidl', 'Binding.h')
        else:
            if not self.interface.isExternal() and self.interface.getExtendedAttribute("HeaderFile"):
                headerDefault = self.interface.getExtendedAttribute("HeaderFile")[0]
            elif self.interface.isIteratorInterface():
                headerDefault = "mozilla/dom/IterableIterator.h"
            else:
                headerDefault = self.nativeType
                headerDefault = headerDefault.replace("::", "/") + ".h"
        self.headerFile = desc.get('headerFile', headerDefault)
        self.headerIsDefault = self.headerFile == headerDefault
        if self.jsImplParent == self.nativeType:
            self.jsImplParentHeader = self.headerFile
        else:
            self.jsImplParentHeader = self.jsImplParent.replace("::", "/") + ".h"

        self.notflattened = desc.get('notflattened', False)
        self.register = desc.get('register', True)

        self.hasXPConnectImpls = desc.get('hasXPConnectImpls', False)

        # If we're concrete, we need to crawl our ancestor interfaces and mark
        # them as having a concrete descendant.
        self.concrete = (not self.interface.isExternal() and
                         not self.interface.isCallback() and
                         not self.interface.isNamespace() and
                         desc.get('concrete', True))
        self.hasUnforgeableMembers = (self.concrete and
                                      any(MemberIsUnforgeable(m, self) for m in
                                          self.interface.members))
        self.operations = {
            'IndexedGetter': None,
            'IndexedSetter': None,
            'IndexedDeleter': None,
            'NamedGetter': None,
            'NamedSetter': None,
            'NamedDeleter': None,
            'Stringifier': None,
            'LegacyCaller': None,
            'Jsonifier': None
            }

        # Stringifiers and jsonifiers need to be set up whether an interface is
        # concrete or not, because they're actually prototype methods and hence
        # can apply to instances of descendant interfaces.  Legacy callers and
        # named/indexed operations only need to be set up on concrete
        # interfaces, since they affect the JSClass we end up using, not the
        # prototype object.
        def addOperation(operation, m):
            if not self.operations[operation]:
                self.operations[operation] = m

        # Since stringifiers go on the prototype, we only need to worry
        # about our own stringifier, not those of our ancestor interfaces.
        if not self.interface.isExternal():
            for m in self.interface.members:
                if m.isMethod() and m.isStringifier():
                    addOperation('Stringifier', m)
                if m.isMethod() and m.isJsonifier():
                    addOperation('Jsonifier', m)

        if self.concrete:
            self.proxy = False
            iface = self.interface
            for m in iface.members:
                # Don't worry about inheriting legacycallers either: in
                # practice these are on most-derived prototypes.
                if m.isMethod() and m.isLegacycaller():
                    if not m.isIdentifierLess():
                        raise TypeError("We don't support legacycaller with "
                                        "identifier.\n%s" % m.location)
                    if len(m.signatures()) != 1:
                        raise TypeError("We don't support overloaded "
                                        "legacycaller.\n%s" % m.location)
                    addOperation('LegacyCaller', m)
            while iface:
                for m in iface.members:
                    if not m.isMethod():
                        continue

                    def addIndexedOrNamedOperation(operation, m):
                        if m.isIndexed():
                            operation = 'Indexed' + operation
                        else:
                            assert m.isNamed()
                            operation = 'Named' + operation
                        addOperation(operation, m)

                    if m.isGetter():
                        addIndexedOrNamedOperation('Getter', m)
                    if m.isSetter():
                        addIndexedOrNamedOperation('Setter', m)
                    if m.isDeleter():
                        addIndexedOrNamedOperation('Deleter', m)
                    if m.isLegacycaller() and iface != self.interface:
                        raise TypeError("We don't support legacycaller on "
                                        "non-leaf interface %s.\n%s" %
                                        (iface, iface.location))

                iface.setUserData('hasConcreteDescendant', True)
                iface = iface.parent

            self.proxy = (self.supportsIndexedProperties() or
                          (self.supportsNamedProperties() and
                           not self.hasNamedPropertiesObject) or
                          self.hasNonOrdinaryGetPrototypeOf())

            if self.proxy:
                if (not self.operations['IndexedGetter'] and
                    (self.operations['IndexedSetter'] or
                     self.operations['IndexedDeleter'])):
                    raise SyntaxError("%s supports indexed properties but does "
                                      "not have an indexed getter.\n%s" %
                                      (self.interface, self.interface.location))
                if (not self.operations['NamedGetter'] and
                    (self.operations['NamedSetter'] or
                     self.operations['NamedDeleter'])):
                    raise SyntaxError("%s supports named properties but does "
                                      "not have a named getter.\n%s" %
                                      (self.interface, self.interface.location))
                iface = self.interface
                while iface:
                    iface.setUserData('hasProxyDescendant', True)
                    iface = iface.parent

        if desc.get('wantsQI', None) is not None:
            self._wantsQI = desc.get('wantsQI', None)
        self.wrapperCache = (not self.interface.isCallback() and
                             not self.interface.isIteratorInterface() and
                             desc.get('wrapperCache', True))

        self.name = interface.identifier.name

        # self.extendedAttributes is a dict of dicts, keyed on
        # all/getterOnly/setterOnly and then on member name. Values are an
        # array of extended attributes.
        self.extendedAttributes = {'all': {}, 'getterOnly': {}, 'setterOnly': {}}

        def addExtendedAttribute(attribute, config):
            def add(key, members, attribute):
                for member in members:
                    self.extendedAttributes[key].setdefault(member, []).append(attribute)

            if isinstance(config, dict):
                for key in ['all', 'getterOnly', 'setterOnly']:
                    add(key, config.get(key, []), attribute)
            elif isinstance(config, list):
                add('all', config, attribute)
            else:
                assert isinstance(config, str)
                if config == '*':
                    iface = self.interface
                    while iface:
                        add('all', map(lambda m: m.name, iface.members), attribute)
                        iface = iface.parent
                else:
                    add('all', [config], attribute)

        if self.interface.isJSImplemented():
            addExtendedAttribute('implicitJSContext', ['constructor'])
        else:
            for attribute in ['implicitJSContext']:
                addExtendedAttribute(attribute, desc.get(attribute, {}))

        if self.interface.identifier.name == 'Navigator':
            for m in self.interface.members:
                if m.isAttr() and m.navigatorObjectGetter:
                    # These getters call ConstructNavigatorObject to construct
                    # the value, and ConstructNavigatorObject needs a JSContext.
                    self.extendedAttributes['all'].setdefault(m.identifier.name, []).append('implicitJSContext')

        self._binaryNames = desc.get('binaryNames', {})
        self._binaryNames.setdefault('__legacycaller', 'LegacyCall')
        self._binaryNames.setdefault('__stringifier', 'Stringify')

        if not self.interface.isExternal():
            def isTestInterface(iface):
                return (iface.identifier.name in ["TestInterface",
                                                  "TestJSImplInterface",
                                                  "TestRenamedInterface"])

            for member in self.interface.members:
                if not member.isAttr() and not member.isMethod():
                    continue
                binaryName = member.getExtendedAttribute("BinaryName")
                if binaryName:
                    assert isinstance(binaryName, list)
                    assert len(binaryName) == 1
                    self._binaryNames.setdefault(member.identifier.name,
                                                 binaryName[0])

        # Build the prototype chain.
        self.prototypeChain = []
        parent = interface
        while parent:
            self.prototypeChain.insert(0, parent.identifier.name)
            parent = parent.parent
        config.maxProtoChainLength = max(config.maxProtoChainLength,
                                         len(self.prototypeChain))

    def binaryNameFor(self, name):
        return self._binaryNames.get(name, name)

    @property
    def prototypeNameChain(self):
        return map(lambda p: self.getDescriptor(p).name, self.prototypeChain)

    @property
    def parentPrototypeName(self):
        if len(self.prototypeChain) == 1:
            return None
        return self.getDescriptor(self.prototypeChain[-2]).name

    def hasInterfaceOrInterfacePrototypeObject(self):

        # Forward-declared interfaces don't need either interface object or
        # interface prototype object as they're going to use QI.
        if self.interface.isExternal():
            return False

        return self.interface.hasInterfaceObject() or self.interface.hasInterfacePrototypeObject()

    @property
    def hasNamedPropertiesObject(self):
        if self.interface.isExternal():
            return False

        return self.isGlobal() and self.supportsNamedProperties()

    def getExtendedAttributes(self, member, getter=False, setter=False):
        def ensureValidBoolExtendedAttribute(attr, name):
            if (attr is not None and attr is not True):
                raise TypeError("Unknown value for '%s': %s" % (name, attr[0]))

        def ensureValidThrowsExtendedAttribute(attr):
            ensureValidBoolExtendedAttribute(attr, "Throws")

        def ensureValidCanOOMExtendedAttribute(attr):
            ensureValidBoolExtendedAttribute(attr, "CanOOM")

        def ensureValidNeedsSubjectPrincipalExtendedAttribute(attr):
            ensureValidBoolExtendedAttribute(attr, "NeedsSubjectPrincipal")

        def maybeAppendInfallibleToAttrs(attrs, throws):
            ensureValidThrowsExtendedAttribute(throws)
            if throws is None:
                attrs.append("infallible")

        def maybeAppendCanOOMToAttrs(attrs, canOOM):
            ensureValidCanOOMExtendedAttribute(canOOM)
            if canOOM is not None:
                attrs.append("canOOM")

        def maybeAppendNeedsSubjectPrincipalToAttrs(attrs, needsSubjectPrincipal):
            ensureValidNeedsSubjectPrincipalExtendedAttribute(needsSubjectPrincipal)
            if needsSubjectPrincipal is not None:
                attrs.append("needsSubjectPrincipal")

        name = member.identifier.name
        throws = self.interface.isJSImplemented() or member.getExtendedAttribute("Throws")
        canOOM = member.getExtendedAttribute("CanOOM")
        needsSubjectPrincipal = member.getExtendedAttribute("NeedsSubjectPrincipal")
        if member.isMethod():
            # JSObject-returning [NewObject] methods must be fallible,
            # since they have to (fallibly) allocate the new JSObject.
            if (member.getExtendedAttribute("NewObject") and
                methodReturnsJSObject(member)):
                throws = True
            attrs = self.extendedAttributes['all'].get(name, [])
            maybeAppendInfallibleToAttrs(attrs, throws)
            maybeAppendCanOOMToAttrs(attrs, canOOM)
            maybeAppendNeedsSubjectPrincipalToAttrs(attrs,
                                                    needsSubjectPrincipal)
            return attrs

        assert member.isAttr()
        assert bool(getter) != bool(setter)
        key = 'getterOnly' if getter else 'setterOnly'
        attrs = self.extendedAttributes['all'].get(name, []) + self.extendedAttributes[key].get(name, [])
        if throws is None:
            throwsAttr = "GetterThrows" if getter else "SetterThrows"
            throws = member.getExtendedAttribute(throwsAttr)
        maybeAppendInfallibleToAttrs(attrs, throws)
        if canOOM is None:
            canOOMAttr = "GetterCanOOM" if getter else "SetterCanOOM"
            canOOM = member.getExtendedAttribute(canOOMAttr)
        maybeAppendCanOOMToAttrs(attrs, canOOM)
        if needsSubjectPrincipal is None:
            needsSubjectPrincipalAttr = (
                "GetterNeedsSubjectPrincipal" if getter else "SetterNeedsSubjectPrincipal")
            needsSubjectPrincipal = member.getExtendedAttribute(
                needsSubjectPrincipalAttr)
        maybeAppendNeedsSubjectPrincipalToAttrs(attrs, needsSubjectPrincipal)
        return attrs

    def supportsIndexedProperties(self):
        return self.operations['IndexedGetter'] is not None

    def lengthNeedsCallerType(self):
        """
        Determine whether our length getter needs a caller type; this is needed
        in some indexed-getter proxy algorithms.  The idea is that if our
        indexed getter needs a caller type, our automatically-generated Length()
        calls need one too.
        """
        assert self.supportsIndexedProperties()
        indexedGetter = self.operations['IndexedGetter']
        return indexedGetter.getExtendedAttribute("NeedsCallerType")

    def supportsNamedProperties(self):
        return self.operations['NamedGetter'] is not None

    def supportedNamesNeedCallerType(self):
        """
        Determine whether our GetSupportedNames call needs a caller type.  The
        idea is that if your named getter needs a caller type, then so does
        GetSupportedNames.
        """
        assert self.supportsNamedProperties()
        namedGetter = self.operations['NamedGetter']
        return namedGetter.getExtendedAttribute("NeedsCallerType")

    def hasNonOrdinaryGetPrototypeOf(self):
        return self.interface.getExtendedAttribute("NonOrdinaryGetPrototypeOf")

    def needsHeaderInclude(self):
        """
        An interface doesn't need a header file if it is not concrete, not
        pref-controlled, has no prototype object, has no static methods or
        attributes and has no parent.  The parent matters because we assert
        things about refcounting that depend on the actual underlying type if we
        have a parent.

        """
        return (self.interface.isExternal() or self.concrete or
                self.interface.hasInterfacePrototypeObject() or
                any((m.isAttr() or m.isMethod()) and m.isStatic() for m in self.interface.members) or
                self.interface.parent)

    def hasThreadChecks(self):
        # isExposedConditionally does not necessarily imply thread checks
        # (since at least [SecureContext] is independent of them), but we're
        # only used to decide whether to include nsThreadUtils.h, so we don't
        # worry about that.
        return ((self.isExposedConditionally() and
                 not self.interface.isExposedInWindow()) or
                self.interface.isExposedInSomeButNotAllWorkers())

    def hasCEReactions(self):
        return any(m.getExtendedAttribute("CEReactions") for m in self.interface.members)

    def isExposedConditionally(self):
        return (self.interface.isExposedConditionally() or
                self.interface.isExposedInSomeButNotAllWorkers())

    def needsXrayResolveHooks(self):
        """
        Generally, any interface with NeedResolve needs Xray
        resolveOwnProperty and enumerateOwnProperties hooks.  But for
        the special case of plugin-loading elements, we do NOT want
        those, because we don't want to instantiate plug-ins simply
        due to chrome touching them and that's all those hooks do on
        those elements.  So we special-case those here.
        """
        return (self.interface.getExtendedAttribute("NeedResolve") and
                self.interface.identifier.name not in ["HTMLObjectElement",
                                                       "HTMLEmbedElement"])
    def needsXrayNamedDeleterHook(self):
        return self.operations["NamedDeleter"] is not None

    def needsSpecialGenericOps(self):
        """
        Returns true if this descriptor requires generic ops other than
        GenericBindingMethod/GenericBindingGetter/GenericBindingSetter.

        In practice we need to do this if our this value might be an XPConnect
        object or if we need to coerce null/undefined to the global.
        """
        return self.hasXPConnectImpls or self.interface.isOnGlobalProtoChain()

    def isGlobal(self):
        """
        Returns true if this is the primary interface for a global object
        of some sort.
        """
        return (self.interface.getExtendedAttribute("Global") or
                self.interface.getExtendedAttribute("PrimaryGlobal"))

    @property
    def namedPropertiesEnumerable(self):
        """
        Returns whether this interface should have enumerable named properties
        """
        assert self.proxy
        assert self.supportsNamedProperties()
        iface = self.interface
        while iface:
            if iface.getExtendedAttribute("LegacyUnenumerableNamedProperties"):
                return False
            iface = iface.parent
        return True

    @property
    def registersGlobalNamesOnWindow(self):
        return (not self.interface.isExternal() and
                self.interface.hasInterfaceObject() and
                self.interface.isExposedInWindow() and
                self.register)

    def getDescriptor(self, interfaceName):
        """
        Gets the appropriate descriptor for the given interface name.
        """
        return self.config.getDescriptor(interfaceName)


# Some utility methods
def getTypesFromDescriptor(descriptor):
    """
    Get all argument and return types for all members of the descriptor
    """
    members = [m for m in descriptor.interface.members]
    if descriptor.interface.ctor():
        members.append(descriptor.interface.ctor())
    members.extend(descriptor.interface.namedConstructors)
    signatures = [s for m in members if m.isMethod() for s in m.signatures()]
    types = []
    for s in signatures:
        assert len(s) == 2
        (returnType, arguments) = s
        types.append(returnType)
        types.extend(a.type for a in arguments)

    types.extend(a.type for a in members if a.isAttr())

    if descriptor.interface.maplikeOrSetlikeOrIterable:
        maplikeOrSetlikeOrIterable = descriptor.interface.maplikeOrSetlikeOrIterable
        if maplikeOrSetlikeOrIterable.hasKeyType():
            types.append(maplikeOrSetlikeOrIterable.keyType)
        if maplikeOrSetlikeOrIterable.hasValueType():
            types.append(maplikeOrSetlikeOrIterable.valueType)
    return types


def getFlatTypes(types):
    retval = set()
    for type in types:
        type = type.unroll()
        if type.isUnion():
            retval |= set(type.flatMemberTypes)
        else:
            retval.add(type)
    return retval


def getTypesFromDictionary(dictionary):
    """
    Get all member types for this dictionary
    """
    types = []
    curDict = dictionary
    while curDict:
        types.extend([m.type for m in curDict.members])
        curDict = curDict.parent
    return types


def getTypesFromCallback(callback):
    """
    Get the types this callback depends on: its return type and the
    types of its arguments.
    """
    sig = callback.signatures()[0]
    types = [sig[0]]  # Return type
    types.extend(arg.type for arg in sig[1])  # Arguments
    return types


def getAllTypes(descriptors, dictionaries, callbacks):
    """
    Generate all the types we're dealing with.  For each type, a tuple
    containing type, dictionary is yielded.  The dictionary can be None if the
    type does not come from a dictionary.
    """
    for d in descriptors:
        if d.interface.isExternal():
            continue
        for t in getTypesFromDescriptor(d):
            yield (t, None)
    for dictionary in dictionaries:
        for t in getTypesFromDictionary(dictionary):
            yield (t, dictionary)
    for callback in callbacks:
        for t in getTypesFromCallback(callback):
            yield (t, None)

def iteratorNativeType(descriptor):
    assert descriptor.interface.isIterable()
    iterableDecl = descriptor.interface.maplikeOrSetlikeOrIterable
    assert iterableDecl.isPairIterator()
    return "mozilla::dom::IterableIterator<%s>" % descriptor.nativeType