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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 */
#ifndef mozilla_dom_ScriptLoader_h
#define mozilla_dom_ScriptLoader_h
#include "js/TypeDecls.h"
#include "js/loader/LoadedScript.h"
#include "js/loader/ScriptKind.h"
#include "js/loader/ScriptLoadRequest.h"
#include "mozilla/dom/ScriptLoadContext.h"
#include "nsCOMPtr.h"
#include "nsRefPtrHashtable.h"
#include "nsIScriptElement.h"
#include "nsCOMArray.h"
#include "nsCycleCollectionParticipant.h"
#include "nsTArray.h"
#include "nsILoadInfo.h" // nsSecurityFlags
#include "nsINode.h"
#include "nsIObserver.h"
#include "nsIScriptLoaderObserver.h"
#include "nsURIHashKey.h"
#include "mozilla/CORSMode.h"
#include "mozilla/dom/JSExecutionContext.h" // JSExecutionContext
#include "ModuleLoader.h"
#include "mozilla/MaybeOneOf.h"
#include "mozilla/MozPromise.h"
class nsCycleCollectionTraversalCallback;
class nsIChannel;
class nsIConsoleReportCollector;
class nsIContent;
class nsIIncrementalStreamLoader;
class nsIPrincipal;
class nsIScriptGlobalObject;
class nsIURI;
namespace JS {
class CompileOptions;
template <typename UnitT>
class SourceText;
namespace loader {
class LoadedScript;
class ScriptLoaderInterface;
class ModuleLoadRequest;
class ModuleScript;
class ScriptLoadRequest;
class ScriptLoadRequestList;
} // namespace loader
} // namespace JS
namespace mozilla {
class LazyLogModule;
union Utf8Unit;
namespace dom {
class AutoJSAPI;
class DocGroup;
class Document;
class ModuleLoader;
class SRICheckDataVerifier;
class SRIMetadata;
class ScriptLoadHandler;
class ScriptLoadContext;
class ScriptLoader;
class ScriptRequestProcessor;
enum class ReferrerPolicy : uint8_t;
class AsyncCompileShutdownObserver final : public nsIObserver {
~AsyncCompileShutdownObserver() { Unregister(); }
explicit AsyncCompileShutdownObserver(ScriptLoader* aLoader)
: mScriptLoader(aLoader) {}
void OnShutdown();
void Unregister();
// Defined during registration in ScriptLoader constructor, and
// cleared during destructor, ScriptLoader::Destroy() or Shutdown.
ScriptLoader* mScriptLoader;
// Script loader implementation
class ScriptLoader final : public JS::loader::ScriptLoaderInterface {
class MOZ_STACK_CLASS AutoCurrentScriptUpdater {
AutoCurrentScriptUpdater(ScriptLoader* aScriptLoader,
nsIScriptElement* aCurrentScript)
: mOldScript(aScriptLoader->mCurrentScript),
mScriptLoader(aScriptLoader) {
nsCOMPtr<nsINode> node = do_QueryInterface(aCurrentScript);
mScriptLoader->mCurrentScript =
node && !node->IsInShadowTree() ? aCurrentScript : nullptr;
~AutoCurrentScriptUpdater() {
nsCOMPtr<nsIScriptElement> mOldScript;
ScriptLoader* mScriptLoader;
friend class JS::loader::ModuleLoadRequest;
friend class ScriptRequestProcessor;
friend class ModuleLoader;
friend class ScriptLoadHandler;
friend class AutoCurrentScriptUpdater;
explicit ScriptLoader(Document* aDocument);
* Called when the document that owns this script loader changes global. The
* argument is null when the document is detached from a window.
void SetGlobalObject(nsIGlobalObject* aGlobalObject);
* The loader maintains a weak reference to the document with
* which it is initialized. This call forces the reference to
* be dropped.
void DropDocumentReference() { mDocument = nullptr; }
* Add an observer for all scripts loaded through this loader.
* @param aObserver observer for all script processing.
nsresult AddObserver(nsIScriptLoaderObserver* aObserver) {
return mObservers.AppendObject(aObserver) ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
* Remove an observer.
* @param aObserver observer to be removed
void RemoveObserver(nsIScriptLoaderObserver* aObserver) {
* Process a script element. This will include both loading the
* source of the element if it is not inline and evaluating
* the script itself.
* If the script is an inline script that can be executed immediately
* (i.e. there are no other scripts pending) then ScriptAvailable
* and ScriptEvaluated will be called before the function returns.
* If true is returned the script could not be executed immediately.
* In this case ScriptAvailable is guaranteed to be called at a later
* point (as well as possibly ScriptEvaluated).
* @param aElement The element representing the script to be loaded and
* evaluated.
bool ProcessScriptElement(nsIScriptElement* aElement);
* Gets the currently executing script. This is useful if you want to
* generate a unique key based on the currently executing script.
nsIScriptElement* GetCurrentScript() { return mCurrentScript; }
nsIScriptElement* GetCurrentParserInsertedScript() {
return mCurrentParserInsertedScript;
* Whether the loader is enabled or not.
* When disabled, processing of new script elements is disabled.
* Any call to ProcessScriptElement() will return false. Note that
* this DOES NOT disable currently loading or executing scripts.
bool GetEnabled() { return mEnabled; }
void SetEnabled(bool aEnabled) {
if (!mEnabled && aEnabled) {
mEnabled = aEnabled;
ModuleLoader* GetModuleLoader() { return mModuleLoader; }
void RegisterContentScriptModuleLoader(ModuleLoader* aLoader);
void RegisterShadowRealmModuleLoader(ModuleLoader* aLoader);
* Check whether to speculatively OMT parse scripts as soon as
* they are fetched, even if not a parser blocking request.
* Controlled by
* dom.script_loader.external_scripts.speculative_omt_parse_enabled
bool SpeculativeOMTParsingEnabled() const {
return mSpeculativeOMTParsingEnabled;
* Add/remove a blocker for parser-blocking scripts (and XSLT
* scripts). Blockers will stop such scripts from executing, but not from
* loading.
void AddParserBlockingScriptExecutionBlocker() {
void RemoveParserBlockingScriptExecutionBlocker() {
if (!--mParserBlockingBlockerCount && ReadyToExecuteScripts()) {
* Add/remove a blocker for execution of all scripts. Blockers will stop
* scripts from executing, but not from loading.
void AddExecuteBlocker() { ++mBlockerCount; }
void RemoveExecuteBlocker() {
if (!--mBlockerCount) {
* Convert the given buffer to a UTF-16 string. If the buffer begins with a
* BOM, it is interpreted as that encoding; otherwise the first of |aChannel|,
* |aHintCharset|, or |aDocument| that provides a recognized encoding is used,
* or Windows-1252 if none of them do.
* Encoding errors in the buffer are converted to replacement characters, so
* allocation failure is the only way this function can fail.
* @param aChannel Channel corresponding to the data. May be null.
* @param aData The data to convert
* @param aLength Length of the data
* @param aHintCharset Character set hint (e.g., from a charset attribute).
* @param aDocument Document which the data is loaded for. May be null.
* @param aBufOut [out] fresh char16_t array containing data converted to
* Unicode. Caller must js_free() this data when finished
* with it.
* @param aLengthOut [out] Length of array returned in aBufOut in number
* of char16_t code units.
static nsresult ConvertToUTF16(nsIChannel* aChannel, const uint8_t* aData,
uint32_t aLength,
const nsAString& aHintCharset,
Document* aDocument, char16_t*& aBufOut,
size_t& aLengthOut);
static inline nsresult ConvertToUTF16(nsIChannel* aChannel,
const uint8_t* aData, uint32_t aLength,
const nsAString& aHintCharset,
Document* aDocument,
JS::UniqueTwoByteChars& aBufOut,
size_t& aLengthOut) {
char16_t* bufOut;
nsresult rv = ConvertToUTF16(aChannel, aData, aLength, aHintCharset,
aDocument, bufOut, aLengthOut);
if (NS_SUCCEEDED(rv)) {
return rv;
* Convert the given buffer to a UTF-8 string. If the buffer begins with a
* BOM, it is interpreted as that encoding; otherwise the first of |aChannel|,
* |aHintCharset|, or |aDocument| that provides a recognized encoding is used,
* or Windows-1252 if none of them do.
* Encoding errors in the buffer are converted to replacement characters, so
* allocation failure is the only way this function can fail.
* @param aChannel Channel corresponding to the data. May be null.
* @param aData The data to convert
* @param aLength Length of the data
* @param aHintCharset Character set hint (e.g., from a charset attribute).
* @param aDocument Document which the data is loaded for. May be null.
* @param aBufOut [out] fresh Utf8Unit array containing data converted to
* Unicode. Caller must js_free() this data when finished
* with it.
* @param aLengthOut [out] Length of array returned in aBufOut in UTF-8 code
* units (i.e. in bytes).
static nsresult ConvertToUTF8(nsIChannel* aChannel, const uint8_t* aData,
uint32_t aLength, const nsAString& aHintCharset,
Document* aDocument, Utf8Unit*& aBufOut,
size_t& aLengthOut);
* Handle the completion of a stream. This is called by the
* ScriptLoadHandler object which observes the IncrementalStreamLoader
* loading the script. The streamed content is expected to be stored on the
* aRequest argument.
nsresult OnStreamComplete(nsIIncrementalStreamLoader* aLoader,
ScriptLoadRequest* aRequest,
nsresult aChannelStatus, nsresult aSRIStatus,
SRICheckDataVerifier* aSRIDataVerifier);
* Returns wether any request is queued, and not executed yet.
bool HasPendingRequests() const;
* Returns wether there are any dynamic module import requests pending.
bool HasPendingDynamicImports() const;
* Processes any pending requests that are ready for processing.
void ProcessPendingRequests();
* Starts deferring deferred scripts and puts them in the mDeferredRequests
* queue instead.
void BeginDeferringScripts();
* Notifies the script loader that parsing is done. If aTerminated is true,
* this will drop any pending scripts that haven't run yet, otherwise it will
* do nothing.
void ParsingComplete(bool aTerminated);
* Notifies the script loader that the checkpoint to begin execution of defer
* scripts has been reached. This is either the end of of the document parse
* or the end of loading of parser-inserted stylesheets, whatever happens
* last.
* Otherwise, it will stop deferring scripts and immediately processes the
* mDeferredRequests queue.
* WARNING: This function will synchronously execute content scripts, so be
* prepared that the world might change around you.
void DeferCheckpointReached();
* Returns the number of pending scripts, deferred or not.
uint32_t HasPendingOrCurrentScripts() {
return mCurrentScript || mParserBlockingRequest;
* Adds aURI to the preload list and starts loading it.
* @param aURI The URI of the external script.
* @param aCharset The charset parameter for the script.
* @param aType The type parameter for the script.
* @param aCrossOrigin The crossorigin attribute for the script.
* Void if not present.
* @param aIntegrity The expect hash url, if avail, of the request
* @param aScriptFromHead Whether or not the script was a child of head
virtual void PreloadURI(nsIURI* aURI, const nsAString& aCharset,
const nsAString& aType, const nsAString& aCrossOrigin,
const nsAString& aIntegrity, bool aScriptFromHead,
bool aAsync, bool aDefer, bool aNoModule,
bool aLinkPreload,
const ReferrerPolicy aReferrerPolicy);
* Process a request that was deferred so that the script could be compiled
* off thread.
nsresult ProcessOffThreadRequest(ScriptLoadRequest* aRequest);
bool AddPendingChildLoader(ScriptLoader* aChild) {
// XXX(Bug 1631371) Check if this should use a fallible operation as it
// pretended earlier. Else, change the return type to void.
return true;
mozilla::dom::DocGroup* GetDocGroup() const;
* Register the fact that we saw the load event, and that we need to save the
* bytecode at the next loop cycle unless new scripts are waiting in the
* pipeline.
void LoadEventFired();
* Destroy and prevent the ScriptLoader or the ScriptLoadRequests from owning
* any references to the JSScript or to the Request which might be used for
* caching the encoded bytecode.
void Destroy();
* Get the currently active script. This is used as the initiating script when
* executing timeout handler scripts.
static JS::loader::LoadedScript* GetActiveScript(JSContext* aCx);
Document* GetDocument() const { return mDocument; }
nsIURI* GetBaseURI() const override;
already_AddRefed<ScriptLoadRequest> CreateLoadRequest(
ScriptKind aKind, nsIURI* aURI, nsIScriptElement* aElement,
nsIPrincipal* aTriggeringPrincipal, mozilla::CORSMode aCORSMode,
const SRIMetadata& aIntegrity, ReferrerPolicy aReferrerPolicy);
* Unblocks the creator parser of the parser-blocking scripts.
void UnblockParser(ScriptLoadRequest* aParserBlockingRequest);
* Asynchronously resumes the creator parser of the parser-blocking scripts.
void ContinueParserAsync(ScriptLoadRequest* aParserBlockingRequest);
bool ProcessExternalScript(nsIScriptElement* aElement, ScriptKind aScriptKind,
const nsAutoString& aTypeAttr,
nsIContent* aScriptContent);
bool ProcessInlineScript(nsIScriptElement* aElement, ScriptKind aScriptKind);
JS::loader::ScriptLoadRequest* LookupPreloadRequest(
nsIScriptElement* aElement, ScriptKind aScriptKind,
const SRIMetadata& aSRIMetadata);
void GetSRIMetadata(const nsAString& aIntegrityAttr,
SRIMetadata* aMetadataOut);
* Given a script element, get the referrer policy should be applied to load
* requests.
ReferrerPolicy GetReferrerPolicy(nsIScriptElement* aElement);
* Helper function to check the content policy for a given request.
static nsresult CheckContentPolicy(Document* aDocument, nsISupports* aContext,
const nsAString& aType,
ScriptLoadRequest* aRequest);
* Helper function to determine whether an about: page loads a chrome: URI.
* Please note that this function only returns true if:
* * the about: page uses a ContentPrincipal with scheme about:
* * the about: page is not linkable from content
* (e.g. the function will return false for about:blank or about:srcdoc)
static bool IsAboutPageLoadingChromeURI(ScriptLoadRequest* aRequest,
Document* aDocument);
* Start a load for aRequest's URI.
nsresult StartLoad(ScriptLoadRequest* aRequest);
* Start a load for a classic script URI.
* Sets up the necessary security flags before calling StartLoadInternal.
nsresult StartClassicLoad(ScriptLoadRequest* aRequest);
* Start a load for a module script URI.
nsresult StartLoadInternal(ScriptLoadRequest* aRequest,
nsSecurityFlags securityFlags);
* Abort the current stream, and re-start with a new load request from scratch
* without requesting any alternate data. Returns NS_BINDING_RETARGETED on
* success, as this error code is used to abort the input stream.
nsresult RestartLoad(ScriptLoadRequest* aRequest);
void HandleLoadError(ScriptLoadRequest* aRequest, nsresult aResult);
* Process any pending requests asynchronously (i.e. off an event) if there
* are any. Note that this is a no-op if there aren't any currently pending
* requests.
* This function is virtual to allow cross-library calls to SetEnabled()
virtual void ProcessPendingRequestsAsync();
* If true, the loader is ready to execute parser-blocking scripts, and so are
* all its ancestors. If the loader itself is ready but some ancestor is not,
* this function will add an execute blocker and ask the ancestor to remove it
* once it becomes ready.
bool ReadyToExecuteParserBlockingScripts();
* Return whether just this loader is ready to execute parser-blocking
* scripts.
bool SelfReadyToExecuteParserBlockingScripts() {
return ReadyToExecuteScripts() && !mParserBlockingBlockerCount;
* Return whether this loader is ready to execute scripts in general.
bool ReadyToExecuteScripts() { return mEnabled && !mBlockerCount; }
nsresult VerifySRI(ScriptLoadRequest* aRequest,
nsIIncrementalStreamLoader* aLoader, nsresult aSRIStatus,
SRICheckDataVerifier* aSRIDataVerifier) const;
nsresult SaveSRIHash(ScriptLoadRequest* aRequest,
SRICheckDataVerifier* aSRIDataVerifier,
uint32_t* sriLength) const;
void ReportErrorToConsole(ScriptLoadRequest* aRequest,
nsresult aResult) const override;
void ReportWarningToConsole(
ScriptLoadRequest* aRequest, const char* aMessageName,
const nsTArray<nsString>& aParams = nsTArray<nsString>()) const override;
void ReportPreloadErrorsToConsole(ScriptLoadRequest* aRequest);
nsresult AttemptAsyncScriptCompile(ScriptLoadRequest* aRequest,
bool* aCouldCompileOut);
nsresult ProcessRequest(ScriptLoadRequest* aRequest);
nsresult CompileOffThreadOrProcessRequest(ScriptLoadRequest* aRequest);
void FireScriptAvailable(nsresult aResult, ScriptLoadRequest* aRequest);
// TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
MOZ_CAN_RUN_SCRIPT_BOUNDARY void FireScriptEvaluated(
nsresult aResult, ScriptLoadRequest* aRequest);
nsresult EvaluateScriptElement(ScriptLoadRequest* aRequest);
// Handles both bytecode and text source scripts; populates exec with a
// compiled script
nsresult CompileOrDecodeClassicScript(JSContext* aCx,
JSExecutionContext& aExec,
ScriptLoadRequest* aRequest);
static nsCString& BytecodeMimeTypeFor(ScriptLoadRequest* aRequest);
// Decide whether to encode bytecode for given script load request,
// and store the script into the request if necessary.
// This method must be called before executing the script.
void MaybePrepareForBytecodeEncodingBeforeExecute(
ScriptLoadRequest* aRequest, JS::Handle<JSScript*> aScript);
// Queue the script load request for bytecode encoding if we decided to
// encode, or cleanup the script load request fields otherwise.
// This method must be called after executing the script.
nsresult MaybePrepareForBytecodeEncodingAfterExecute(
ScriptLoadRequest* aRequest, nsresult aRv);
// Returns true if MaybePrepareForBytecodeEncodingAfterExecute is called
// for given script load request.
bool IsAlreadyHandledForBytecodeEncodingPreparation(
ScriptLoadRequest* aRequest);
void MaybePrepareModuleForBytecodeEncodingBeforeExecute(
JSContext* aCx, ModuleLoadRequest* aRequest) override;
nsresult MaybePrepareModuleForBytecodeEncodingAfterExecute(
ModuleLoadRequest* aRequest, nsresult aRv) override;
nsresult EvaluateScript(nsIGlobalObject* aGlobalObject,
ScriptLoadRequest* aRequest);
* Queue the current script load request to be saved, when the page
* initialization ends. The page initialization end is defined as being the
* time when the load event got received, and when no more scripts are waiting
* to be executed.
void RegisterForBytecodeEncoding(ScriptLoadRequest* aRequest);
* Check if all conditions are met, i-e that the onLoad event fired and that
* no more script have to be processed. If all conditions are met, queue an
* event to encode all the bytecode and save them on the cache.
void MaybeTriggerBytecodeEncoding() override;
* Iterate over all script load request and save the bytecode of executed
* functions on the cache provided by the channel.
void EncodeBytecode();
void EncodeRequestBytecode(JSContext* aCx, ScriptLoadRequest* aRequest);
void GiveUpBytecodeEncoding();
already_AddRefed<nsIGlobalObject> GetGlobalForRequest(
ScriptLoadRequest* aRequest);
already_AddRefed<nsIScriptGlobalObject> GetScriptGlobalObject();
// Fill in CompileOptions, as well as produce the introducer script for
// subsequent calls to UpdateDebuggerMetadata
nsresult FillCompileOptionsForRequest(
JSContext* aCx, ScriptLoadRequest* aRequest, JS::CompileOptions* aOptions,
JS::MutableHandle<JSScript*> aIntroductionScript) override;
uint32_t NumberOfProcessors();
int32_t PhysicalSizeOfMemoryInGB();
nsresult PrepareLoadedRequest(ScriptLoadRequest* aRequest,
nsIIncrementalStreamLoader* aLoader,
nsresult aStatus);
void AddDeferRequest(ScriptLoadRequest* aRequest);
void AddAsyncRequest(ScriptLoadRequest* aRequest);
bool MaybeRemovedDeferRequests();
bool ShouldApplyDelazifyStrategy(ScriptLoadRequest* aRequest);
void ApplyDelazifyStrategy(JS::CompileOptions* aOptions);
bool ShouldCompileOffThread(ScriptLoadRequest* aRequest);
void MaybeMoveToLoadedList(ScriptLoadRequest* aRequest);
using MaybeSourceText =
mozilla::MaybeOneOf<JS::SourceText<char16_t>, JS::SourceText<Utf8Unit>>;
// Returns wether we should save the bytecode of this script after the
// execution of the script.
static bool ShouldCacheBytecode(ScriptLoadRequest* aRequest);
void RunScriptWhenSafe(ScriptLoadRequest* aRequest);
* Wait for any unused off thread compilations to finish and then
* cancel them.
void CancelScriptLoadRequests();
Document* mDocument; // [WEAK]
nsCOMArray<nsIScriptLoaderObserver> mObservers;
ScriptLoadRequestList mNonAsyncExternalScriptInsertedRequests;
// mLoadingAsyncRequests holds async requests while they're loading; when they
// have been loaded they are moved to mLoadedAsyncRequests.
ScriptLoadRequestList mLoadingAsyncRequests;
ScriptLoadRequestList mLoadedAsyncRequests;
ScriptLoadRequestList mDeferRequests;
ScriptLoadRequestList mXSLTRequests;
RefPtr<ScriptLoadRequest> mParserBlockingRequest;
ScriptLoadRequestList mOffThreadCompilingRequests;
// List of script load request that are holding a buffer which has to be saved
// on the cache.
ScriptLoadRequestList mBytecodeEncodingQueue;
// In mRequests, the additional information here is stored by the element.
struct PreloadInfo {
RefPtr<ScriptLoadRequest> mRequest;
nsString mCharset;
friend void ImplCycleCollectionUnlink(ScriptLoader::PreloadInfo& aField);
friend void ImplCycleCollectionTraverse(
nsCycleCollectionTraversalCallback& aCallback,
ScriptLoader::PreloadInfo& aField, const char* aName, uint32_t aFlags);
struct PreloadRequestComparator {
bool Equals(const PreloadInfo& aPi,
ScriptLoadRequest* const& aRequest) const {
return aRequest == aPi.mRequest;
struct PreloadURIComparator {
bool Equals(const PreloadInfo& aPi, nsIURI* const& aURI) const;
nsTArray<PreloadInfo> mPreloads;
nsCOMPtr<nsIScriptElement> mCurrentScript;
nsCOMPtr<nsIScriptElement> mCurrentParserInsertedScript;
nsTArray<RefPtr<ScriptLoader>> mPendingChildLoaders;
uint32_t mParserBlockingBlockerCount;
uint32_t mBlockerCount;
uint32_t mNumberOfProcessors;
uint32_t mTotalFullParseSize;
int32_t mPhysicalSizeOfMemory;
bool mEnabled;
bool mDeferEnabled;
bool mSpeculativeOMTParsingEnabled;
bool mDeferCheckpointReached;
bool mBlockingDOMContentLoaded;
bool mLoadEventFired;
bool mGiveUpEncoding;
TimeDuration mMainThreadParseTime;
nsCOMPtr<nsIConsoleReportCollector> mReporter;
// ShutdownObserver for off thread compilations
RefPtr<AsyncCompileShutdownObserver> mShutdownObserver;
RefPtr<ModuleLoader> mModuleLoader;
nsTArray<RefPtr<ModuleLoader>> mWebExtModuleLoaders;
nsTArray<RefPtr<ModuleLoader>> mShadowRealmModuleLoaders;
// Logging
static LazyLogModule gCspPRLog;
static LazyLogModule gScriptLoaderLog;
class nsAutoScriptLoaderDisabler {
explicit nsAutoScriptLoaderDisabler(Document* aDoc);
bool mWasEnabled;
RefPtr<ScriptLoader> mLoader;
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_ScriptLoader_h