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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, 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.
+
+`allowUnobservedAsmJS`
+:   A boolean value indicating whether asm.js code running inside this
+    `Debugger` instance's debuggee globals is invisible to Debugger API
+    handlers and breakpoints. Setting this to `false` inhibits the
+    ahead-of-time asm.js compiler and forces asm.js code to run as normal
+    JavaScript. This is an accessor property with a getter and setter. It is
+    initially `false` in a freshly created `Debugger` instance.
+
+    Setting this flag to `true` is intended for uses of subsystems of the
+    Debugger API (e.g, [`Debugger.Source`][source]) for purposes other than
+    step debugging a target JavaScript program.
+
+`collectCoverageInfo`
+:   A boolean value indicating whether code coverage should be enabled inside
+    each debuggee of this `Debugger` instance. Changing this flag value will
+    recompile all JIT code to add or remove code coverage
+    instrumentation. Changing this flag when any frame of the debuggee is
+    currently active on the stack will produce an exception.
+
+    Setting this to `true` enables code coverage instrumentation, which can be
+    accessed via the [`Debugger.Script`][script] `getOffsetsCoverage`
+    function. In some cases, the code coverage might expose information which
+    pre-date the modification of this flag. Code coverage reports are monotone,
+    thus one can take a snapshot when the Debugger is enabled, and output the
+    difference.
+
+    Setting this to `false` prevents this `Debugger` instance from requiring any
+    code coverage instrumentation, but it does not guarantee that the
+    instrumentation is not present.
+
+`uncaughtExceptionHook`
+:   Either `null` or a function that SpiderMonkey calls when a call to a
+    debug event handler, breakpoint 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 debuggees.
+
+    This method's return value is ignored.
+
+<code>onNewPromise(<i>promise</i>)</code>
+:   A new Promise object, referenced by the [`Debugger.Object`][object] instance
+    *promise*, has been allocated in the scope of the debuggees. The Promise's
+    allocation stack can be obtained using the *promiseAllocationStack*
+    accessor property of the [`Debugger.Object`][object] instance *promise*.
+
+    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.
+
+<code>onPromiseSettled(<i>promise</i>)</code>
+:   A Promise object, referenced by the [`Debugger.Object`][object] instance
+    *promise* that was allocated within a debuggee scope, has settled (either
+    fulfilled or rejected). The Promise's state, fulfillment or rejection
+    value, and the allocation and resolution stacks can be obtained using the
+    Promise-related accessor properties of the [`Debugger.Object`][object]
+    instance *promise*.
+
+    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.
+
+<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>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.)
+
+    This handler is not called when unwinding a frame due to an over-recursion
+    or out-of-memory exception.
+
+<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.
+
+    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.)
+
+    If this debugger is [tracking allocation sites][tracking-allocs] and cannot
+    track allocation sites for <i>global</i>, this method throws an `Error`.
+
+`addAllGlobalsAsDebuggees()`
+:   This method is like [`addDebuggee`][add], but adds all the global
+    objects from all compartments to this `Debugger` instance's set of
+    debuggees. Note that it skips this debugger's compartment.
+
+    If this debugger is [tracking allocation sites][tracking-allocs] and cannot
+    track allocation sites for some global, this method throws an `Error`.
+    Otherwise this method returns `undefined`.
+
+    This 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 `addAllGlobalsAsDebuggees` 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, `addAllGlobalsAsDebuggees` is only
+    available to privileged code.
+
+<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.
+
+    Removing a global as a debuggee from this `Debugger` clears all breakpoints
+    that belong to that `Debugger` in that global.
+
+`removeAllDebuggees()`
+:   Remove all the global objects from this `Debugger` instance's set
+    of debuggees.  Return `undefined`.
+
+<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`
+    :   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>findObjects([<i>query</i>])</code>
+:   Return an array of [`Debugger.Object`][object] instances referring to each
+    live object allocated in the scope of the debuggee globals that matches
+    *query*. Each instance appears only once in the array. *Query* is an object
+    whose properties restrict which objects are returned; an object must meet
+    all the criteria given by *query* to be returned. If *query* is omitted, we
+    return the [`Debugger.Object`][object] instances for all objects allocated
+    in the scope of debuggee globals.
+
+    The *query* object may have the following properties:
+
+    `class`
+    :   If present, only return objects whose internal `[[Class]]`'s name
+        matches the given string. Note that in some cases, the prototype object
+        for a given constructor has the same `[[Class]]` as the instances that
+        refer to it, but cannot itself be used as a valid instance of the
+        class. Code gathering objects by class name may need to examine them
+        further before trying to use them.
+
+    All properties of *query* are optional. Passing an empty object returns all
+    objects in debuggee globals.
+
+    Unlike `findScripts`, this function is deterministic and will never return
+    [`Debugger.Object`s][object] referring to previously unreachable objects
+    that had not been collected yet.
+
+<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.
+
+`findAllGlobals()`
+:   Return an array of [`Debugger.Object`][object] instances referring to all the
+    global objects present in this JavaScript instance.
+
+    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].
+
+<code>adoptDebuggeeValue(<i>value</i>)</code>
+:    Given a debuggee value `value` owned by an arbitrary `Debugger`, return an
+     equivalent debuggee value owned by this `Debugger`.
+
+     If `value` is a primitive value, return it unchanged. If `value` is a
+     `Debugger.Object` owned by an arbitrary `Debugger`, return an equivalent
+     `Debugger.Object` owned by this `Debugger`. Otherwise, if `value` is some
+     other kind of object, and hence not a proper debuggee value, throw a
+     TypeError instead.
+
+## Static methods of the Debugger Object
+
+The functions described below are not called with a `this` value.
+
+<code id="isCompilableUnit">isCompilableUnit(<i>source</i>)</code>
+:   Given a string of source code, designated by <i>source</i>, return false if
+    the string might become a valid JavaScript statement with the addition of
+    more lines. Otherwise return true. The intent is to support interactive
+    compilation - accumulate lines in a buffer until isCompilableUnit is true,
+    then pass it to the compiler.