firefox/dom/script/ScriptLoadContext.h

/* -*- 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 http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_ScriptLoadContext_h
#define mozilla_dom_ScriptLoadContext_h

#include "js/AllocPolicy.h"
#include "js/ColumnNumber.h"    // JS::ColumnNumberOneOrigin
#include "js/CompileOptions.h"  // JS::OwningCompileOptions
#include "js/experimental/JSStencil.h"  // JS::FrontendContext, JS::Stencil, JS::InstantiationStorage
#include "js/RootingAPI.h"
#include "js/SourceText.h"
#include "js/Transcoding.h"  // JS::TranscodeResult
#include "js/TypeDecls.h"
#include "js/loader/LoadContextBase.h"
#include "js/loader/ScriptKind.h"
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Atomics.h"
#include "mozilla/Assertions.h"
#include "mozilla/CORSMode.h"
#include "mozilla/dom/SRIMetadata.h"
#include "mozilla/LinkedList.h"
#include "mozilla/Maybe.h"
#include "mozilla/MaybeOneOf.h"
#include "mozilla/Mutex.h"
#include "mozilla/PreloaderBase.h"
#include "mozilla/RefPtr.h"
#include "mozilla/StaticPrefs_dom.h"
#include "mozilla/TaskController.h"  // mozilla::Task
#include "mozilla/Utf8.h"            // mozilla::Utf8Unit
#include "mozilla/Variant.h"
#include "mozilla/Vector.h"
#include "nsCOMPtr.h"
#include "nsCycleCollectionParticipant.h"
#include "nsIScriptElement.h"

class nsICacheInfoChannel;
struct JSContext;

namespace mozilla::dom {

class Element;

/*
 * DOM specific ScriptLoadContext.
 *
 * ScriptLoadContexts augment the loading of a ScriptLoadRequest. They
 * describe how a ScriptLoadRequests loading and evaluation needs to be
 * augmented, based on the information provided by the loading context. In
 * the case of the DOM, the ScriptLoadContext is used to identify how a script
 * should be loaded according to information found in the HTML document into
 * which it will be loaded. The following fields describe how the
 * ScriptLoadRequest will be loaded.
 *
 *    * mScriptMode
 *        stores the mode (Async, Sync, Deferred), and preload, which
 *        allows the ScriptLoader to decide if the script should be pushed
 *        offThread, or if the preloaded request should be used.
 *    * mScriptFromHead
 *        Set when the script tag is in the head, and should be treated as
 *        a blocking script
 *    * mIsInline
 *        Set for scripts whose bodies are inline in the html. In this case,
 *        the script does not need to be fetched first.
 *    * mIsXSLT
 *        Set if we are in an XSLT request.
 *    * mIsPreload
 *        Set for scripts that are preloaded in a
 *        <link rel="preload" as="script"> or <link rel="modulepreload">
 *        element.
 *
 * In addition to describing how the ScriptLoadRequest will be loaded by the
 * DOM ScriptLoader, the ScriptLoadContext contains fields that facilitate
 * those custom behaviors, including support for offthread parsing and preload
 * element specific controls.
 *
 */

// Base class for the off-thread compile or off-thread decode tasks.
class CompileOrDecodeTask : public mozilla::Task {
 protected:
  CompileOrDecodeTask();
  virtual ~CompileOrDecodeTask();

  nsresult InitFrontendContext();

  void DidRunTask(const MutexAutoLock& aProofOfLock,
                  RefPtr<JS::Stencil>&& aStencil);

  bool IsCancelled(const MutexAutoLock& aProofOfLock) const {
    return mIsCancelled;
  }

 public:
  // Returns the result of the compilation or decode if it was successful.
  // Returns nullptr otherwise, and sets pending exception on JSContext.
  //
  // aInstantiationStorage receives the storage allocated off main thread
  // on successful case.
  already_AddRefed<JS::Stencil> StealResult(
      JSContext* aCx, JS::InstantiationStorage* aInstantiationStorage);

  // Cancel the task.
  // If the task is already running, this waits for the task to finish.
  void Cancel();

 protected:
  // This mutex is locked during running the task or cancelling task.
  mozilla::Mutex mMutex;

  // The result of decode task, to distinguish throwing case and decode error.
  JS::TranscodeResult mResult = JS::TranscodeResult::Ok;

  // An option used to compile the code, or the equivalent for decode.
  // This holds the filename pointed by errors reported to JS::FrontendContext.
  JS::OwningCompileOptions mOptions;

  // Owning-pointer for the context associated with the script compilation.
  //
  // The context is allocated on main thread in InitFrontendContext method,
  // and is freed on any thread in the destructor.
  JS::FrontendContext* mFrontendContext = nullptr;

  bool mIsCancelled = false;

 private:
  // The result of the compilation or decode.
  RefPtr<JS::Stencil> mStencil;

  JS::InstantiationStorage mInstantiationStorage;
};

class ScriptLoadContext : public JS::loader::LoadContextBase,
                          public PreloaderBase {
 protected:
  virtual ~ScriptLoadContext();

 public:
  explicit ScriptLoadContext(nsIScriptElement* aScriptElement = nullptr);

  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(ScriptLoadContext,
                                           JS::loader::LoadContextBase)

  static void PrioritizeAsPreload(nsIChannel* aChannel);

  bool IsPreload() const override;

  bool CompileStarted() const;

  bool IsTracking() const { return mIsTracking; }
  void SetIsTracking() {
    MOZ_ASSERT(!mIsTracking);
    mIsTracking = true;
  }

  void BlockOnload(Document* aDocument);

  void MaybeUnblockOnload();

  enum class ScriptMode : uint8_t {
    eBlocking,
    eDeferred,
    eAsync,
    eLinkPreload  // this is a load initiated by <link rel="preload"
                  // as="script"> or <link rel="modulepreload"> tag
  };

  void SetScriptMode(bool aDeferAttr, bool aAsyncAttr, bool aLinkPreload);

  bool IsLinkPreloadScript() const {
    return mScriptMode == ScriptMode::eLinkPreload;
  }

  bool IsBlockingScript() const { return mScriptMode == ScriptMode::eBlocking; }

  bool IsDeferredScript() const { return mScriptMode == ScriptMode::eDeferred; }

  bool IsAsyncScript() const { return mScriptMode == ScriptMode::eAsync; }

  // Accessors for the script element, for each purpose.
  //
  // The script element reference is guaranteed to be available only for:
  //   * inline/external classic script
  //   * inline/external top-level module
  //
  // The reference is valid only for specific purpose explained below.

  // For aLoadingNode parameter of a new channel.
  // TODO: This is basically unnecessary and a document can be used instead.
  //       Remove this.
  inline nsIScriptElement* GetScriptElementForLoadingNode() const {
    MOZ_ASSERT(mScriptElement);
    return mScriptElement;
  }

  // For TRACE_FOR_TEST macros.
  // NOTE: This is called also for imported modules.
  //       The consumer allows nullptr.
  inline nsIScriptElement* GetScriptElementForTrace() const {
    return mScriptElement;
  }

  // Event target for beforescriptexecute/afterscriptexecute events.
  inline nsIScriptElement* GetScriptElementForExecuteEvents() const {
    MOZ_ASSERT(mScriptElement);
    return mScriptElement;
  }

  // For ScriptLoader::mCurrentParserInsertedScript.
  inline nsIScriptElement* GetScriptElementForCurrentParserInsertedScript()
      const {
    MOZ_ASSERT(mScriptElement);
    return mScriptElement;
  }

  // For nsIScriptLoaderObserver.
  inline nsIScriptElement* GetScriptElementForObserver() const {
    MOZ_ASSERT(mScriptElement);
    return mScriptElement;
  }

  // For URL classifier.
  inline nsIScriptElement* GetScriptElementForUrlClassifier() const {
    return mScriptElement;
  }

  // For AutoCurrentScriptUpdater.
  // This is valid only for classic script.
  inline nsIScriptElement* GetScriptElementForCurrentScript() const {
    MOZ_ASSERT(mScriptElement);
    return mScriptElement;
  }

  bool HasScriptElement() const;

  void GetInlineScriptText(nsAString& aText) const;

  void GetHintCharset(nsAString& aCharset) const;

  // TODO: Reimplement with mLineNo/mColumnNo.
  uint32_t GetScriptLineNumber() const;
  JS::ColumnNumberOneOrigin GetScriptColumnNumber() const;

  void BeginEvaluatingTopLevel() const;
  void EndEvaluatingTopLevel() const;

  void UnblockParser() const;
  void ContinueParserAsync() const;

  Document* GetScriptOwnerDocument() const;

  // Make this request a preload (speculative) request.
  void SetIsPreloadRequest() {
    MOZ_ASSERT(!HasScriptElement());
    MOZ_ASSERT(!IsPreload());
    mIsPreload = true;
  }

  // Make a preload request into an actual load request for the given element.
  void SetIsLoadRequest(nsIScriptElement* aElement);

  FromParser GetParserCreated() const {
    if (!mScriptElement) {
      return NOT_FROM_PARSER;
    }
    return mScriptElement->GetParserCreated();
  }

  // Used to output a string for the Gecko Profiler.
  void GetProfilerLabel(nsACString& aOutString) override;

  void MaybeCancelOffThreadScript();

  // Finish the off-main-thread compilation and return the result, or
  // convert the compilation error to runtime error.
  already_AddRefed<JS::Stencil> StealOffThreadResult(
      JSContext* aCx, JS::InstantiationStorage* aInstantiationStorage);

  ScriptMode mScriptMode;  // Whether this is a blocking, defer or async script.
  bool mScriptFromHead;    // Synchronous head script block loading of other non
                           // js/css content.
  bool mIsInline;          // Is the script inline or loaded?
  bool mInDeferList;       // True if we live in mDeferRequests.
  bool mInAsyncList;       // True if we live in mLoadingAsyncRequests or
                           // mLoadedAsyncRequests.
  bool mIsNonAsyncScriptInserted;  // True if we live in
                                   // mNonAsyncExternalScriptInsertedRequests
  bool mIsXSLT;                    // True if we live in mXSLTRequests.
  bool mInCompilingList;  // True if we are in mOffThreadCompilingRequests.
  bool mIsTracking;       // True if the script comes from a source on our
                          // tracking protection list.
  bool mWasCompiledOMT;   // True if the script has been compiled off main
                          // thread.

  // Task that performs off-thread compilation or off-thread decode.
  // This field is used to take the result of the task, or cancel the task.
  //
  // Set to non-null on the task creation, and set to null when taking the
  // result or cancelling the task.
  RefPtr<CompileOrDecodeTask> mCompileOrDecodeTask;

  uint32_t mLineNo;
  JS::ColumnNumberOneOrigin mColumnNo;

  // Set on scripts and top level modules.
  bool mIsPreload;

  // Non-null if there is a document that this request is blocking from loading.
  RefPtr<Document> mLoadBlockedDocument;

  // The script element which trigerred this script load.
  // This is valid only for classic script and top-level module script.
  nsCOMPtr<nsIScriptElement> mScriptElement;

  // For preload requests, we defer reporting errors to the console until the
  // request is used.
  nsresult mUnreportedPreloadError;
};

}  // namespace mozilla::dom

#endif  // mozilla_dom_ScriptLoadContext_h