The Tor Browser: comparison js/src/doc/Debugger/Debugger.md

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+# The Debugger Object
+When called as a constructor, the `Debugger` object creates a new
+`Debugger` instance.
+<code>new Debugger([<i>global</i>, ...])</code>
+:   Create a debugger object, and apply its [`addDebuggee`][add] method to
+each of the given <i>global</i> objects to add them as the initial
+debuggees.
+## Accessor Properties of the Debugger Prototype Object
+A `Debugger` instance inherits the following accessor properties from
+its prototype:
+`enabled`
+:   A boolean value indicating whether this `Debugger` instance's handlers,
+breakpoints, watchpoints, and the like are currently enabled. It is an
+accessor property with a getter and setter: assigning to it enables or
+disables this `Debugger` instance; reading it produces true if the
+instance is enabled, or false otherwise. This property is initially
+`true` in a freshly created `Debugger` instance.
+This property gives debugger code a single point of control for
+disentangling itself from the debuggee, regardless of what sort of
+events or handlers or "points" we add to the interface.
+`uncaughtExceptionHook`
+:   Either `null` or a function that SpiderMonkey calls when a call to a
+debug event handler, breakpoint handler, watchpoint handler, or similar
+function throws some exception, which we refer to as
+<i>debugger-exception</i> here. Exceptions thrown in the debugger are
+not propagated to debuggee code; instead, SpiderMonkey calls this
+function, passing <i>debugger-exception</i> as its sole argument and
+the `Debugger` instance as the `this` value. This function should
+return a [resumption value][rv], which determines how the debuggee
+should continue.
+If the uncaught exception hook itself throws an exception,
+<i>uncaught-hook-exception</i>, SpiderMonkey throws a new error object,
+<i>confess-to-debuggee-exception</i>, to the debuggee whose message
+blames the debugger, and includes textual descriptions of
+<i>uncaught-hook-exception</i> and the original
+<i>debugger-exception</i>.
+If `uncaughtExceptionHook`'s value is `null`, SpiderMonkey throws an
+exception to the debuggee whose message blames the debugger, and
+includes a textual description of <i>debugger-exception</i>.
+Assigning anything other than a callable value or `null` to this
+property throws a `TypeError` exception.
+(This is not an ideal way to handle debugger bugs, but the hope here is
+that some sort of backstop, even if imperfect, will make life easier for
+debugger developers. For example, an uncaught exception hook may have
+access to browser-level features like the `alert` function, which this
+API's implementation does not, making it possible to present debugger
+errors to the developer in a way suited to the context.)
+## Debugger Handler Functions
+Each `Debugger` instance inherits accessor properties with which you can
+store handler functions for SpiderMonkey to call when given events occur
+in debuggee code.
+When one of the events described below occurs in debuggee code, the engine
+pauses the debuggee and calls the corresponding debugging handler on each
+`Debugger` instance that is observing the debuggee. The handler functions
+receive the `Debugger` instance as their `this` value. Most handler
+functions can return a [resumption value][rv] indicating how the debuggee's
+execution should proceed.
+On a new `Debugger` instance, each of these properties is initially
+`undefined`. Any value assigned to a debugging handler must be either a
+function or `undefined`; otherwise a `TypeError` is thrown.
+Handler functions run in the same thread in which the event occurred.
+They run in the compartment to which they belong, not in a debuggee
+compartment.
+<code>onNewScript(<i>script</i>, <i>global</i>)</code>
+:   New code, represented by the [`Debugger.Script`][script] instance
+<i>script</i>, has been loaded in the scope of the debuggee global
+object <i>global</i>. <i>global</i> is a [`Debugger.Object`][object]
+instance whose referent is the global object.
+This method's return value is ignored.
+<code>onDebuggerStatement(<i>frame</i>)</code>
+:   Debuggee code has executed a <i>debugger</i> statement in <i>frame</i>.
+This method should return a [resumption value][rv] specifying how the
+debuggee's execution should proceed.
+<code>onEnterFrame(<i>frame</i>)</code>
+:   The stack frame <i>frame</i> is about to begin executing code.
+(Naturally, <i>frame</i> is currently the youngest
+[visible frame][vf].) This method should return
+a [resumption value][rv] specifying how the debuggee's execution should
+proceed.
+SpiderMonkey only calls `onEnterFrame` to report
+[visible][vf], non-`"debugger"` frames.
+<code>onThrow(<i>frame</i>, <i>value</i>) <i>(future plan)</i></code>
+:   The exception <i>value</i> is being thrown by <i>frame</i>, which is
+running debuggee code. This method should return a
+[resumption value][rv] specifying how the debuggee's execution should
+proceed. If it returns `undefined`, the exception is thrown as normal.
+A call to the `onThrow` handler is typically followed by one or more
+calls to the `onExceptionUnwind` handler.
+*(pending discussion)* If the debuggee executes
+`try { throw 0; } finally { f(); }` and `f()` executes without error,
+the `onThrow` handler is called only once. The debugger is not notified
+when the exception is set aside in order to execute the `finally` block,
+nor when it is restored after the `finally` block completes normally.
+*(An alternative design here would be: onException(status, frame, value)
+where status is one of the strings "throw", "unwind", "catch",
+"finally", "rethrow". JS\_SaveExceptionState would trigger a "finally"
+event, JS\_RestoreExceptionState would trigger a "rethrow",
+JS\_ClearPendingException would trigger a "catch"; not sure what
+JS\_DropExceptionState or a return/throw from a finally block should
+do.)*
+<code>onExceptionUnwind(<i>frame</i>, <i>value</i>)</code>
+:   The exception <i>value</i> has been thrown, and has propagated to
+<i>frame</i>; <i>frame</i> is the youngest remaining stack frame, and is a
+debuggee frame. This method should return a [resumption value][rv]
+specifying how the debuggee's execution should proceed. If it returns
+`undefined`, the exception continues to propagate as normal: if control in
+`frame` is in a `try` block, control jumps to the corresponding `catch` or
+`finally` block; otherwise, <i>frame</i> is popped, and the exception
+propagates to <i>frame</i>'s caller.
+When an exception's propagation causes control to enter a `finally`
+block, the exception is temporarily set aside. If the `finally` block
+finishes normally, the exception resumes propagation, and the debugger's
+`onExceptionUnwind` handler is called again, in the same frame. (The
+other possibility is for the `finally` block to exit due to a `return`,
+`continue`, or `break` statement, or a new exception. In those cases the
+old exception does not continue to propagate; it is discarded.)
+<code>sourceHandler(<i>ASuffusionOfYellow</i>)</code>
+:   This method is never called. If it is ever called, a contradiction has
+been proven, and the debugger is free to assume that everything is true.
+<code>onError(<i>frame</i>, <i>report</i>)</code>
+:   SpiderMonkey is about to report an error in <i>frame</i>. <i>Report</i>
+is an object describing the error, with the following properties:
+`message`
+:   The fully formatted error message.
+`file`
+:   If present, the source file name, URL, etc. (If this property is
+present, the <i>line</i> property will be too, and vice versa.)
+`line`
+:   If present, the source line number at which the error occurred.
+`lineText`
+:   If present, this is the source code of the offending line.
+`offset`
+:   The index of the character within lineText at which the error occurred.
+`warning`
+:   Present and true if this is a warning; absent otherwise.
+`strict`
+:   Present and true if this error or warning is due to the strict option
+(not to be confused with ES strict mode)
+`exception`
+:   Present and true if an exception will be thrown; absent otherwise.
+`arguments`
+:   An array of strings, representing the arguments substituted into the
+error message.
+This method's return value is ignored.
+`onNewGlobalObject(global)`
+:   A new global object, <i>global</i>, has been created. The application
+embedding the JavaScript implementation may provide details about what
+kind of global it is via <code><i>global</i>.hostAnnotations</code>.
+This handler method should return a [resumption value][rv] specifying how
+the debuggee's execution should proceed. However, note that a <code>{ return:
+<i>value</i> }</code> resumption value is treated like `undefined` ("continue
+normally"); <i>value</i> is ignored. (Allowing the handler to substitute
+its own value for the new global object doesn't seem useful.)
+This handler method is only available to debuggers running in privileged
+code ("chrome", in Firefox). Most functions provided by this `Debugger`
+API observe activity in only those globals that are reachable by the
+API's user, thus imposing capability-based restrictions on a
+`Debugger`'s reach. However, the `onNewGlobalObject` method allows the
+API user to monitor all global object creation that occurs anywhere
+within the JavaScript system (the "JSRuntime", in SpiderMonkey terms),
+thereby escaping the capability-based limits. For this reason,
+`onNewGlobalObject` is only available to privileged code.
+## Function Properties of the Debugger Prototype Object
+The functions described below may only be called with a `this` value
+referring to a `Debugger` instance; they may not be used as methods of
+other kinds of objects.
+<code id="addDebuggee">addDebuggee(<i>global</i>)</code>
+:   Add the global object designated by <i>global</i> to the set of global
+objects this `Debugger` instance is debugging. If the designated global
+is already a debuggee, this has no effect. Return this `Debugger`'s
+[`Debugger.Object`][object] instance referring to the designated global.
+The value <i>global</i> may be any of the following:
+* A global object.
+* An HTML5 `WindowProxy` object (an "outer window", in Firefox
+terminology), which is treated as if the `Window` object of the
+browsing context's active document (the "inner window") were passed.
+* A cross-compartment wrapper of an object; we apply the prior rules to
+the wrapped object.
+* A [`Debugger.Object`][object] instance belonging to this `Debugger` instance;
+we apply the prior rules to the referent.
+* Any other sort of value is treated as a `TypeError`. (Note that each
+rule is only applied once in the process of resolving a given
+<i>global</i> argument. Thus, for example, a [`Debugger.Object`][object]
+referring to a second [`Debugger.Object`][object] which refers to a global does
+not designate that global for the purposes of this function.)
+The global designated by <i>global</i> must be in a different
+compartment than this `Debugger` instance itself. If adding the
+designated global's compartment would create a cycle of debugger and
+debuggee compartments, this method throws an error.
+This method returns the [`Debugger.Object`][object] instance whose referent is
+the designated global object.
+The `Debugger` instance does not hold a strong reference to its
+debuggee globals: if a debuggee global is not otherwise reachable, then
+it is dropped from the `Debugger`'s set of debuggees. (Naturally, the
+[`Debugger.Object`][object] instance this method returns does hold a strong
+reference to the added global.)
+<code>removeDebuggee(<i>global</i>)</code>
+:   Remove the global object designated by <i>global</i> from this
+`Debugger` instance's set of debuggees. Return `undefined`.
+This method interprets <i>global</i> using the same rules that
+[`addDebuggee`][add] does.
+<code>hasDebuggee(<i>global</i>)</code>
+:   Return `true` if the global object designated by <i>global</i> is a
+debuggee of this `Debugger` instance.
+This method interprets <i>global</i> using the same rules that
+[`addDebuggee`][add] does.
+`getDebuggees()`
+:   Return an array of distinct [`Debugger.Object`][object] instances whose referents
+are all the global objects this `Debugger` instance is debugging.
+Since `Debugger` instances don't hold strong references to their
+debuggee globals, if a debuggee global is otherwise unreachable, it may
+be dropped at any moment from the array this method returns.
+`getNewestFrame()`
+:   Return a [`Debugger.Frame`][frame] instance referring to the youngest
+[visible frame][vf] currently on the calling thread's stack, or `null`
+if there are no visible frames on the stack.
+<code>findSources([<i>query</i>]) <i>(not yet implemented)</i></code>
+:   Return an array of all [`Debugger.Source`][source] instances matching
+<i>query</i>. Each source appears only once in the array. <i>Query</i>
+is an object whose properties restrict which sources are returned; a
+source must meet all the criteria given by <i>query</i> to be returned.
+If <i>query</i> is omitted, we return all sources of all debuggee
+scripts.
+<i>Query</i> may have the following properties:
+`url`
+:   The source's `url` property must be equal to this value.
+`global`
+:   The source must have been evaluated in the scope of the given global
+object. If this property's value is a [`Debugger.Object`][object] instance
+belonging to this `Debugger` instance, then its referent is used. If the
+object is not a global object, then the global in whose scope it was
+allocated is used.
+Note that the result may include sources that can no longer ever be
+used by the debuggee: say, eval code that has finished running, or
+source for unreachable functions. Whether such sources appear can be
+affected by the garbage collector's behavior, so this function's result
+is not entirely deterministic.
+<code>findScripts([<i>query</i>])</code>
+:   Return an array of [`Debugger.Script`][script] instances for all debuggee scripts
+matching <i>query</i>. Each instance appears only once in the array.
+<i>Query</i> is an object whose properties restrict which scripts are
+returned; a script must meet all the criteria given by <i>query</i> to
+be returned. If <i>query</i> is omitted, we return the [`Debugger.Script`][script]
+instances for all debuggee scripts.
+<i>Query</i> may have the following properties:
+`url`
+:   The script's `url` property must be equal to this value.
+`source` <i>(not yet implemented)</i>
+:   The script's `source` property must be equal to this value.
+`line`
+:   The script must at least partially cover the given source line. If this
+property is present, the `url` property must be present as well.
+`column`
+:   The script must include given column on the line given by the `line`
+property. If this property is present, the `url` and `line` properties
+must both be present as well.
+`innermost`
+:   If this property is present and true, the script must be the innermost
+script covering the given source location; scripts of enclosing code are
+omitted.
+`global`
+:   The script must be in the scope of the given global object. If this
+property's value is a [`Debugger.Object`][object] instance belonging to this
+`Debugger` instance, then its referent is used. If the object is not a
+global object, then the global in whose scope it was allocated is used.
+All properties of <i>query</i> are optional. Passing an empty object
+returns all debuggee code scripts.
+Note that the result may include [`Debugger.Script`][script] instances for
+scripts that can no longer ever be used by the debuggee, say, those for
+eval code that has finished running, or unreachable functions. Whether
+such scripts appear can be affected by the garbage collector's
+behavior, so this function's behavior is not entirely deterministic.
+<code>clearBreakpoint(<i>handler</i>)</code>
+:   Remove all breakpoints set in this `Debugger` instance that use
+<i>handler</i> as their handler. Note that, if breakpoints using other
+handler objects are set at the same location(s) as <i>handler</i>, they
+remain in place.
+`clearAllBreakpoints()`
+:   Remove all breakpoints set using this `Debugger` instance.
+`clearAllWatchpoints()` <i>(future plan)</i>
+:   Clear all watchpoints owned by this `Debugger` instance.
+`findAllGlobals()`
+:   Return an array of [`Debugger.Object`][object] instances referring to all the
+global objects present in this JavaScript instance. The application may
+provide details about what kind of globals they are via the
+[`Debugger.Object`][object] instances' `hostAnnotations` accessors.
+The results of this call can be affected in non-deterministic ways by
+the details of the JavaScript implementation. The array may include
+[`Debugger.Object`][object] instances referring to global objects that are not
+actually reachable by the debuggee or any other code in the system.
+(Naturally, once the function has returned, the array's
+[`Debugger.Object`][object] instances strongly reference the globals they refer
+to.)
+This handler method is only available to debuggers running in privileged
+code ("chrome", in Firefox). Most functions provided by this `Debugger`
+API observe activity in only those globals that are reachable by the
+API's user, thus imposing capability-based restrictions on a
+`Debugger`'s reach. However, `findAllGlobals` allows the API user to
+find all global objects anywhere within the JavaScript system (the
+"JSRuntime", in SpiderMonkey terms), thereby escaping the
+capability-based limits. For this reason, `findAllGlobals` is only
+available to privileged code.
+<code>makeGlobalObjectReference(<i>global</i>)</code>
+:   Return the [`Debugger.Object`][object] whose referent is the global object
+designated by <i>global</i>, without adding the designated global as a
+debuggee. If <i>global</i> does not designate a global object, throw a
+`TypeError`. Determine which global is designated by <i>global</i>
+using the same rules as [`Debugger.prototype.addDebuggee`][add].

The Tor Browser / file comparison

comparison: js/src/doc/Debugger/Debugger.md

js/src/doc/Debugger/Debugger.md