path: root/dom/bindings/Configuration.py

# 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 IDLIncludesStatement
import io
import os
import six
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.

    Subclasses must also have a getConfig() method that returns a
    Configuration.
    """

    def __init__(self):
        pass


def isChildPath(path, basePath):
    path = os.path.normpath(path)
    return os.path.commonprefix((path, basePath)) == basePath


class Configuration(DescriptorProvider):
    """
    Represents global configuration state based on IDL parse data and
    the configuration file.
    """

    def __init__(self, filename, webRoots, parseData, generatedEvents=[]):
        DescriptorProvider.__init__(self)

        # Read the configuration file.
        glbl = {}
        exec(io.open(filename, encoding="utf-8").read(), glbl)
        config = glbl["DOMInterfaces"]

        webRoots = tuple(map(os.path.normpath, webRoots))

        def isInWebIDLRoot(path):
            return any(isChildPath(path, root) for root in webRoots)

        # 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.dictionariesByName = {}
        self.generatedEvents = generatedEvents
        self.maxProtoChainLength = 0
        for thing in parseData:
            if isinstance(thing, IDLIncludesStatement):
                # Our build system doesn't support dep build involving
                # addition/removal of "includes" 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!
                if thing.interface.filename() != thing.filename():
                    raise TypeError(
                        "The binding build system doesn't really support "
                        "'includes' statements which don't appear in the "
                        "file in which the left-hand side of the statement is "
                        "defined.\n"
                        "%s\n"
                        "%s" % (thing.location, thing.interface.location)
                    )

            assert not thing.isType()

            if (
                not thing.isInterface()
                and not thing.isNamespace()
                and not thing.isInterfaceMixin()
            ):
                continue
            # Our build system doesn't support dep builds involving
            # addition/removal of partial interfaces/namespaces/mixins that
            # appear in a different .webidl file than the
            # interface/namespace/mixin they are extending.  Make sure we don't
            # have any of those.  See similar block above for "includes"
            # statements!
            if not thing.isExternal():
                for partial in thing.getPartials():
                    if partial.filename() != thing.filename():
                        raise TypeError(
                            "The binding build system doesn't really support "
                            "partial interfaces/namespaces/mixins which don't "
                            "appear in the file in which the "
                            "interface/namespace/mixin they are extending is "
                            "defined.  Don't do this.\n"
                            "%s\n"
                            "%s" % (partial.location, thing.location)
                        )

            # The rest of the logic doesn't apply to mixins.
            if thing.isInterfaceMixin():
                continue

            iface = thing
            if not iface.isExternal():
                if not (
                    iface.getExtendedAttribute("ChromeOnly")
                    or iface.getExtendedAttribute("Func")
                    == ["nsContentUtils::IsCallerChromeOrFuzzingEnabled"]
                    or not iface.hasInterfaceObject()
                    or isInWebIDLRoot(iface.filename())
                ):
                    raise TypeError(
                        "Interfaces which are exposed to the web may only be "
                        "defined in a DOM WebIDL root %r. Consider marking "
                        "the interface [ChromeOnly] or "
                        "[Func='nsContentUtils::IsCallerChromeOrFuzzingEnabled'] "
                        "if you do not want it exposed to the web.\n"
                        "%s" % (webRoots, iface.location)
                    )

            self.interfaces[iface.identifier.name] = iface

            entry = config.get(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(key=lambda x: x.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.dictionariesByName = {d.identifier.name: d for d in self.dictionaries}

        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):
            t = findInnermostType(t)
            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 = [
                                    u
                                    for u in self.unionsPerFilename[f]
                                    if u.name != t.name
                                ]
                                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())

        for d in getDictionariesConvertedToJS(
            self.descriptors, self.dictionaries, self.callbacks
        ):
            d.needsConversionToJS = True

        for d in getDictionariesConvertedFromJS(
            self.descriptors, self.dictionaries, self.callbacks
        ):
            d.needsConversionFromJS = True

    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 = [(lambda x: x.interface.isExternal(), False)]
        for key, val in six.iteritems(filters):
            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: x.interface.hasInterfaceObject()
            elif key == "hasInterfacePrototypeObject":
                getter = lambda x: x.interface.hasInterfacePrototypeObject()
            elif key == "hasInterfaceOrInterfacePrototypeObject":
                getter = lambda x: x.hasInterfaceOrInterfacePrototypeObject()
            elif key == "isCallback":
                getter = lambda x: x.interface.isCallback()
            elif key == "isJSImplemented":
                getter = lambda x: x.interface.isJSImplemented()
            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 == "isExposedInWindow":
                getter = lambda x: x.interface.isExposedInWindow()
            elif key == "isSerializable":
                getter = lambda x: x.interface.isSerializable()
            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 = [x for x in curr if f[0](x) == f[1]]
        return curr

    def getEnums(self, webIDLFile):
        return [e for e in self.enums if e.filename() == webIDLFile]

    def getDictionaries(self, webIDLFile):
        return [d for d in self.dictionaries if d.filename() == webIDLFile]

    def getCallbacks(self, webIDLFile):
        return [c for c in self.callbacks if c.filename() == webIDLFile]

    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

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

    def getConfig(self):
        return self

    def getDictionariesConvertibleToJS(self):
        return [d for d in self.dictionaries if d.needsConversionToJS]

    def getDictionariesConvertibleFromJS(self):
        return [d for d in self.dictionaries if d.needsConversionFromJS]

    def getDictionaryIfExists(self, dictionaryName):
        return self.dictionariesByName.get(dictionaryName, None)


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


def methodReturnsJSObject(method):
    assert method.isMethod()

    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)

        # If we're concrete, we need to crawl our ancestor interfaces and mark
        # them as having a concrete descendant.
        concreteDefault = (
            not self.interface.isExternal()
            and not self.interface.isCallback()
            and not self.interface.isNamespace()
            and
            # We're going to assume that leaf interfaces are
            # concrete; otherwise what's the point?  Also
            # interfaces with constructors had better be
            # concrete; otherwise how can you construct them?
            (
                not self.interface.hasChildInterfaces()
                or self.interface.ctor() is not None
            )
        )

        self.concrete = desc.get("concrete", concreteDefault)
        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,
        }

        self.hasDefaultToJSON = False

        # Stringifiers 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.isDefaultToJSON():
                    self.hasDefaultToJSON = True

            # We keep track of instrumente props for all non-external interfaces.
            self.instrumentedProps = []
            instrumentedProps = self.interface.getExtendedAttribute("InstrumentedProps")
            if instrumentedProps:
                # It's actually a one-element list, with the list
                # we want as the only element.
                self.instrumentedProps = instrumentedProps[0]

                # Check that we don't have duplicated instrumented props.
                uniqueInstrumentedProps = set(self.instrumentedProps)
                if len(uniqueInstrumentedProps) != len(self.instrumentedProps):
                    duplicates = [
                        p
                        for p in uniqueInstrumentedProps
                        if self.instrumentedProps.count(p) > 1
                    ]
                    raise TypeError(
                        "Duplicated instrumented properties: %s.\n%s"
                        % (duplicates, self.interface.location)
                    )

        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.isMaybeCrossOriginObject()
            )

            if self.proxy:
                if self.isMaybeCrossOriginObject() and (
                    self.supportsIndexedProperties() or self.supportsNamedProperties()
                ):
                    raise TypeError(
                        "We don't support named or indexed "
                        "properties on maybe-cross-origin objects. "
                        "This lets us assume that their proxy "
                        "hooks are never called via Xrays.  "
                        "Fix %s.\n%s" % (self.interface, self.interface.location)
                    )

                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.implicitJSContext is a list of names of methods and attributes
        # that need a JSContext.
        if self.interface.isJSImplemented():
            self.implicitJSContext = ["constructor"]
        else:
            self.implicitJSContext = desc.get("implicitJSContext", [])
        assert isinstance(self.implicitJSContext, list)

        self._binaryNames = {}

        if not self.interface.isExternal():

            def maybeAddBinaryName(member):
                binaryName = member.getExtendedAttribute("BinaryName")
                if binaryName:
                    assert isinstance(binaryName, list)
                    assert len(binaryName) == 1
                    self._binaryNames.setdefault(member.identifier.name, binaryName[0])

            for member in self.interface.members:
                if not member.isAttr() and not member.isMethod():
                    continue
                maybeAddBinaryName(member)

            ctor = self.interface.ctor()
            if ctor:
                maybeAddBinaryName(ctor)

            # Some default binary names for cases when nothing else got set.
            self._binaryNames.setdefault("__legacycaller", "LegacyCall")
            self._binaryNames.setdefault("__stringifier", "Stringify")

            # Build the prototype chain.
            self.prototypeChain = []
            self.needsMissingPropUseCounters = False
            parent = interface
            while parent:
                self.needsMissingPropUseCounters = (
                    self.needsMissingPropUseCounters
                    or parent.getExtendedAttribute("InstrumentedProps")
                )
                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 [self.getDescriptor(p).name for p in self.prototypeChain]

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

    def hasInterfaceOrInterfacePrototypeObject(self):
        return (
            self.interface.hasInterfaceObject()
            or self.interface.hasInterfacePrototypeObject()
        )

    @property
    def hasNamedPropertiesObject(self):
        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 maybeAppendNeedsErrorResultToAttrs(attrs, throws):
            ensureValidThrowsExtendedAttribute(throws)
            if throws is not None:
                attrs.append("needsErrorResult")

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

        def maybeAppendNeedsSubjectPrincipalToAttrs(attrs, needsSubjectPrincipal):
            if (
                needsSubjectPrincipal is not None
                and needsSubjectPrincipal is not True
                and needsSubjectPrincipal != ["NonSystem"]
            ):
                raise TypeError(
                    "Unknown value for 'NeedsSubjectPrincipal': %s"
                    % needsSubjectPrincipal[0]
                )

            if needsSubjectPrincipal is not None:
                attrs.append("needsSubjectPrincipal")
                if needsSubjectPrincipal == ["NonSystem"]:
                    attrs.append("needsNonSystemSubjectPrincipal")

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

        assert member.isAttr()
        assert bool(getter) != bool(setter)
        if throws is None:
            throwsAttr = "GetterThrows" if getter else "SetterThrows"
            throws = member.getExtendedAttribute(throwsAttr)
        maybeAppendNeedsErrorResultToAttrs(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 isMaybeCrossOriginObject(self):
        # If we're isGlobal and have cross-origin members, we're a Window, and
        # that's not a cross-origin object.  The WindowProxy is.
        return (
            self.concrete
            and self.interface.hasCrossOriginMembers
            and not self.isGlobal()
        )

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

    @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 (
            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)

    def getConfig(self):
        return self.config


# Some utility methods
def getTypesFromDescriptor(descriptor, includeArgs=True, includeReturns=True):
    """
    Get argument and/or return types for all members of the descriptor.  By
    default returns all argument types (which includes types of writable
    attributes) and all return types (which includes types of all attributes).
    """
    assert includeArgs or includeReturns  # Must want _something_.
    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
        if includeReturns:
            types.append(returnType)
        if includeArgs:
            types.extend(a.type for a in arguments)

    types.extend(
        a.type
        for a in members
        if (a.isAttr() and (includeReturns or (includeArgs and not a.readonly)))
    )

    if descriptor.interface.maplikeOrSetlikeOrIterable:
        maplikeOrSetlikeOrIterable = descriptor.interface.maplikeOrSetlikeOrIterable
        if maplikeOrSetlikeOrIterable.isMaplike():
            # The things we expand into may or may not correctly indicate in
            # their formal IDL types what things we have as return values.  For
            # example, "keys" returns the moral equivalent of sequence<keyType>
            # but just claims to return "object".  Similarly, "values" returns
            # the moral equivalent of sequence<valueType> but claims to return
            # "object".  And due to bug 1155340, "get" claims to return "any"
            # instead of the right type.  So let's just manually work around
            # that lack of specificity.  For our arguments, we already enforce
            # the right types at the IDL level, so those will get picked up
            # correctly.
            assert maplikeOrSetlikeOrIterable.hasKeyType()
            assert maplikeOrSetlikeOrIterable.hasValueType()
            if includeReturns:
                types.append(maplikeOrSetlikeOrIterable.keyType)
                types.append(maplikeOrSetlikeOrIterable.valueType)
        elif maplikeOrSetlikeOrIterable.isSetlike():
            assert maplikeOrSetlikeOrIterable.hasKeyType()
            assert maplikeOrSetlikeOrIterable.hasValueType()
            assert (
                maplikeOrSetlikeOrIterable.keyType
                == maplikeOrSetlikeOrIterable.valueType
            )
            # As in the maplike case, we don't always declare our return values
            # quite correctly.
            if includeReturns:
                types.append(maplikeOrSetlikeOrIterable.keyType)
        else:
            assert maplikeOrSetlikeOrIterable.isIterable()
            # As in the maplike/setlike cases we don't do a good job of
            # declaring our actual return types, while our argument types, if
            # any, are declared fine.
            if includeReturns:
                if maplikeOrSetlikeOrIterable.hasKeyType():
                    types.append(maplikeOrSetlikeOrIterable.keyType)
                if maplikeOrSetlikeOrIterable.hasValueType():
                    types.append(maplikeOrSetlikeOrIterable.valueType)

    return types


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


def findInnermostType(t):
    """
    Find the innermost type of the given type, unwrapping Promise and Record
    types, as well as everything that unroll() unwraps.
    """
    while True:
        if t.isRecord():
            t = t.inner
        elif t.unroll() != t:
            t = t.unroll()
        elif t.isPromise():
            t = t.promiseInnerType()
        else:
            return t


def getDependentDictionariesFromDictionary(d):
    """
    Find all the dictionaries contained in the given dictionary, as ancestors or
    members.  This returns a generator.
    """
    while d:
        yield d
        for member in d.members:
            for next in getDictionariesFromType(member.type):
                yield next
        d = d.parent


def getDictionariesFromType(type):
    """
    Find all the dictionaries contained in type.  This can be used to find
    dictionaries that need conversion to JS (by looking at types that get
    converted to JS) or dictionaries that need conversion from JS (by looking at
    types that get converted from JS).

    This returns a generator.
    """
    type = findInnermostType(type)
    if type.isUnion():
        # Look for dictionaries in all the member types
        for t in type.flatMemberTypes:
            for next in getDictionariesFromType(t):
                yield next
    elif type.isDictionary():
        # Find the dictionaries that are itself, any of its ancestors, or
        # contained in any of its member types.
        for d in getDependentDictionariesFromDictionary(type.inner):
            yield d


def getDictionariesConvertedToJS(descriptors, dictionaries, callbacks):
    for desc in descriptors:
        if desc.interface.isExternal():
            continue

        if desc.interface.isJSImplemented():
            # For a JS-implemented interface, we need to-JS
            # conversions for all the types involved.
            for t in getTypesFromDescriptor(desc):
                for d in getDictionariesFromType(t):
                    yield d
        elif desc.interface.isCallback():
            # For callbacks we only want to include the arguments, since that's
            # where the to-JS conversion happens.
            for t in getTypesFromDescriptor(desc, includeReturns=False):
                for d in getDictionariesFromType(t):
                    yield d
        else:
            # For normal interfaces, we only want to include return values,
            # since that's where to-JS conversion happens.
            for t in getTypesFromDescriptor(desc, includeArgs=False):
                for d in getDictionariesFromType(t):
                    yield d

    for callback in callbacks:
        # We only want to look at the arguments
        sig = callback.signatures()[0]
        for arg in sig[1]:
            for d in getDictionariesFromType(arg.type):
                yield d

    for dictionary in dictionaries:
        if dictionary.needsConversionToJS:
            # It's explicitly flagged as needing to-JS conversion, and all its
            # dependent dictionaries will need to-JS conversion too.
            for d in getDependentDictionariesFromDictionary(dictionary):
                yield d


def getDictionariesConvertedFromJS(descriptors, dictionaries, callbacks):
    for desc in descriptors:
        if desc.interface.isExternal():
            continue

        if desc.interface.isJSImplemented():
            # For a JS-implemented interface, we need from-JS conversions for
            # all the types involved.
            for t in getTypesFromDescriptor(desc):
                for d in getDictionariesFromType(t):
                    yield d
        elif desc.interface.isCallback():
            # For callbacks we only want to include the return value, since
            # that's where teh from-JS conversion happens.
            for t in getTypesFromDescriptor(desc, includeArgs=False):
                for d in getDictionariesFromType(t):
                    yield d
        else:
            # For normal interfaces, we only want to include arguments values,
            # since that's where from-JS conversion happens.
            for t in getTypesFromDescriptor(desc, includeReturns=False):
                for d in getDictionariesFromType(t):
                    yield d

    for callback in callbacks:
        # We only want to look at the return value
        sig = callback.signatures()[0]
        for d in getDictionariesFromType(sig[0]):
            yield d

    for dictionary in dictionaries:
        if dictionary.needsConversionFromJS:
            # It's explicitly flagged as needing from-JS conversion, and all its
            # dependent dictionaries will need from-JS conversion too.
            for d in getDependentDictionariesFromDictionary(dictionary):
                yield d