# Debugger.Object A `Debugger.Object` instance represents an object in the debuggee, providing reflection-oriented methods to inspect and modify its referent. The referent's properties do not appear directly as properties of the `Debugger.Object` instance; the debugger can access them only through methods like `Debugger.Object.prototype.getOwnPropertyDescriptor` and `Debugger.Object.prototype.defineProperty`, ensuring that the debugger will not inadvertently invoke the referent's getters and setters. SpiderMonkey creates exactly one `Debugger.Object` instance for each debuggee object it presents to a given [`Debugger`][debugger-object] instance: if the debugger encounters the same object through two different routes (perhaps two functions are called on the same object), SpiderMonkey presents the same `Debugger.Object` instance to the debugger each time. This means that the debugger can use the `==` operator to recognize when two `Debugger.Object` instances refer to the same debuggee object, and place its own properties on a `Debugger.Object` instance to store metadata about particular debuggee objects. JavaScript code in different compartments can have different views of the same object. For example, in Firefox, code in privileged compartments sees content DOM element objects without redefinitions or extensions made to that object's properties by content code. (In Firefox terminology, privileged code sees the element through an "xray wrapper".) To ensure that debugger code sees each object just as the debuggee would, each `Debugger.Object` instance presents its referent as it would be seen from a particular compartment. This "viewing compartment" is chosen to match the way the debugger came across the referent. As a consequence, a single [`Debugger`][debugger-object] instance may actually have several `Debugger.Object` instances: one for each compartment from which the referent is viewed. If more than one [`Debugger`][debugger-object] instance is debugging the same code, each [`Debugger`][debugger-object] gets a separate `Debugger.Object` instance for a given object. This allows the code using each [`Debugger`][debugger-object] instance to place whatever properties it likes on its own `Debugger.Object` instances, without worrying about interfering with other debuggers. While most `Debugger.Object` instances are created by SpiderMonkey in the process of exposing debuggee's behavior and state to the debugger, the debugger can use `Debugger.Object.prototype.makeDebuggeeValue` to create `Debugger.Object` instances for given debuggee objects, or use `Debugger.Object.prototype.copy` and `Debugger.Object.prototype.create` to create new objects in debuggee compartments, allocated as if by particular debuggee globals. `Debugger.Object` instances protect their referents from the garbage collector; as long as the `Debugger.Object` instance is live, the referent remains live. This means that garbage collection has no visible effect on `Debugger.Object` instances. ## Accessor Properties of the Debugger.Object prototype A `Debugger.Object` instance inherits the following accessor properties from its prototype: ### `proto` The referent's prototype (as a new `Debugger.Object` instance), or `null` if it has no prototype. This accessor may throw if the referent is a scripted proxy or some other sort of exotic object (an opaque wrapper, for example). ### `class` A string naming the ECMAScript `[[Class]]` of the referent. ### `callable` `true` if the referent is a callable object (such as a function or a function proxy); false otherwise. ### `name` The name of the referent, if it is a named function. If the referent is an anonymous function, or not a function at all, this is `undefined`. This accessor returns whatever name appeared after the `function` keyword in the source code, regardless of whether the function is the result of instantiating a function declaration (which binds the function to its name in the enclosing scope) or evaluating a function expression (which binds the function to its name only within the function's body). ### `displayName` The referent's display name, if the referent is a function with a display name. If the referent is not a function, or if it has no display name, this is `undefined`. If a function has a given name, its display name is the same as its given name. In this case, the `displayName` and `name` properties are equal. If a function has no name, SpiderMonkey attempts to infer an appropriate name for it given its context. For example: ```js function f() {} // display name: f (the given name) var g = function () {}; // display name: g o.p = function () {}; // display name: o.p var q = { r: function () {} // display name: q.r }; ``` Note that the display name may not be a proper JavaScript identifier, or even a proper expression: we attempt to find helpful names even when the function is not immediately assigned as the value of some variable or property. Thus, we use a/b to refer to the b defined within a, and a< to refer to a function that occurs somewhere within an expression that is assigned to a. For example: ```js function h() { var i = function() {}; // display name: h/i f(function () {}); // display name: h/< } var s = f(function () {}); // display name: s< ``` ### `parameterNames` If the referent is a debuggee function, the names of its parameters, as an array of strings. If the referent is not a debuggee function, or not a function at all, this is `undefined`. If the referent is a host function for which parameter names are not available, return an array with one element per parameter, each of which is `undefined`. If the referent is a function proxy, return an empty array. If the function uses destructuring parameters, the corresponding array elements are `undefined`. For example, if the referent is a function declared in this way: ```js function f(a, [b, c], {d, e:f}) { ... } ``` then this `Debugger.Object` instance's `parameterNames` property would have the value: ```js ["a", undefined, undefined] ``` ### `script` If the referent is a function that is debuggee code, this is that function's script, as a [`Debugger.Script`][script] instance. If the referent is a function proxy or not debuggee code, this is `undefined`. ### `environment` If the referent is a function that is debuggee code, a [`Debugger.Environment`][environment] instance representing the lexical environment enclosing the function when it was created. If the referent is a function proxy or not debuggee code, this is `undefined`. ### `isError` `true` if the referent is any potentially wrapped Error; `false` otherwise. ### `errorMessageName` If the referent is an error created with an engine internal message template this is a string which is the name of the template; `undefined` otherwise. ### `errorLineNumber` If the referent is an Error object, this is the 1-origin line number at which the referent was created; `undefined` otherwise. ### `errorColumnNumber` If the referent is an Error object, this is the 1-origin column number in UTF-16 code units at which the referent was created; `undefined` otherwise. ### `isBoundFunction` If the referent is a debuggee function, returns `true` if the referent is a bound function; `false` otherwise. If the referent is not a debuggee function, or not a function at all, returns `undefined` instead. ### `isArrowFunction` If the referent is a debuggee function, returns `true` if the referent is an arrow function; `false` otherwise. If the referent is not a debuggee function, or not a function at all, returns `undefined` instead. ### `isGeneratorFunction` If the referent is a debuggee function, returns `true` if the referent was created with a `function*` expression or statement, or false if it is some other sort of function. If the referent is not a debuggee function, or not a function at all, this is `undefined`. (This is always equal to `obj.script.isGeneratorFunction`, assuming `obj.script` is a `Debugger.Script`.) ### `isAsyncFunction` If the referent is a debuggee function, returns `true` if the referent is an async function, defined with an `async function` expression or statement, or false if it is some other sort of function. If the referent is not a debuggee function, or not a function at all, this is `undefined`. (This is always equal to `obj.script.isAsyncFunction`, assuming `obj.script` is a `Debugger.Script`.) ### `isClassConstructor` If the referent is a debuggee function, returns `true` if the referent is a class, or false if it is some other sort of function. If the referent is not a debuggee function, or not a function at all, this is `undefined`. (This is always equal to `obj.script.isClassConstructor`, assuming `obj.script` is a `Debugger.Script`.) ### `isPromise` `true` if the referent is a Promise; `false` otherwise. ### `boundTargetFunction` If the referent is a bound debuggee function, this is its target function— the function that was bound to a particular `this` object. If the referent is either not a bound function, not a debuggee function, or not a function at all, this is `undefined`. ### `boundThis` If the referent is a bound debuggee function, this is the `this` value it was bound to. If the referent is either not a bound function, not a debuggee function, or not a function at all, this is `undefined`. ### `boundArguments` If the referent is a bound debuggee function, this is an array (in the Debugger object's compartment) that contains the debuggee values of the `arguments` object it was bound to. If the referent is either not a bound function, not a debuggee function, or not a function at all, this is `undefined`. ### `isProxy` If the referent is a (scripted) proxy, either revoked or not, return `true`. If the referent is not a (scripted) proxy, return `false`. ### `proxyTarget` If the referent is a non-revoked (scripted) proxy, return a `Debugger.Object` instance referring to the ECMAScript `[[ProxyTarget]]` of the referent. If the referent is a revoked (scripted) proxy, return `null`. If the referent is not a (scripted) proxy, return `undefined`. ### `proxyHandler` If the referent is a non-revoked (scripted) proxy, return a `Debugger.Object` instance referring to the ECMAScript `[[ProxyHandler]]` of the referent. If the referent is a revoked (scripted) proxy, return `null`. If the referent is not a (scripted) proxy, return `undefined`. ### `promiseState` If the referent is a [`Promise`][promise], return a string indicating whether the [`Promise`][promise] is pending, or has been fulfilled or rejected. This string takes one of the following values: * `"pending"`, if the [`Promise`][promise] is pending. * `"fulfilled"`, if the [`Promise`][promise] has been fulfilled. * `"rejected"`, if the [`Promise`][promise] has been rejected. If the referent is not a [`Promise`][promise], throw a `TypeError`. ### `promiseValue` Return a debuggee value representing the value the [`Promise`][promise] has been fulfilled with. If the referent is not a [`Promise`][promise], or the [`Promise`][promise] has not been fulfilled, throw a `TypeError`. ### `promiseReason` Return a debuggee value representing the value the [`Promise`][promise] has been rejected with. If the referent is not a [`Promise`][promise], or the [`Promise`][promise] has not been rejected, throw a `TypeError`. ### `promiseAllocationSite` If the referent is a [`Promise`][promise], this is the [JavaScript execution stack][saved-frame] captured at the time of the promise's allocation. This can return null if the promise was not created from script. If the referent is not a [`Promise`][promise], throw a `TypeError` exception. ### `promiseResolutionSite` If the referent is a [`Promise`][promise], this is the [JavaScript execution stack][saved-frame] captured at the time of the promise's resolution. This can return null if the promise was not resolved by calling its `resolve` or `reject` resolving functions from script. If the referent is not a [`Promise`][promise], throw a `TypeError` exception. ### `promiseID` If the referent is a [`Promise`][promise], this is a process-unique identifier for the [`Promise`][promise]. With e10s, the same id can potentially be assigned to multiple [`Promise`][promise] instances, if those instances were created in different processes. If the referent is not a [`Promise`][promise], throw a `TypeError` exception. ### `promiseDependentPromises` If the referent is a [`Promise`][promise], this is an `Array` of `Debugger.Objects` referring to the promises directly depending on the referent [`Promise`][promise]. These are: 1) Return values of `then()` calls on the promise. 2) Return values of `Promise.all()` if the referent [`Promise`][promise] was passed in as one of the arguments. 3) Return values of `Promise.race()` if the referent [`Promise`][promise] was passed in as one of the arguments. Once a [`Promise`][promise] is settled, it will generally notify its dependent promises and forget about them, so this is most useful on *pending* promises. Note that the `Array` only contains the promises that directly depend on the referent [`Promise`][promise]. It does not contain promises that depend on promises that depend on the referent [`Promise`][promise]. If the referent is not a [`Promise`][promise], throw a `TypeError` exception. ### `promiseLifetime` If the referent is a [`Promise`][promise], this is the number of milliseconds elapsed since the [`Promise`][promise] was created. If the referent is not a [`Promise`][promise], throw a `TypeError` exception. ### `promiseTimeToResolution` If the referent is a [`Promise`][promise], this is the number of milliseconds elapsed between when the [`Promise`][promise] was created and when it was resolved. If the referent hasn't been resolved or is not a [`Promise`][promise], throw a `TypeError` exception. ### `allocationSite` If [object allocation site tracking][tracking-allocs] was enabled when this `Debugger.Object`'s referent was allocated, return the [JavaScript execution stack][saved-frame] captured at the time of the allocation. Otherwise, return `null`. ## Function Properties of the Debugger.Object prototype The functions described below may only be called with a `this` value referring to a `Debugger.Object` instance; they may not be used as methods of other kinds of objects. The descriptions use "referent" to mean "the referent of this `Debugger.Object` instance". Unless otherwise specified, these methods are not [invocation functions][inv fr]; if a call would cause debuggee code to run (say, because it gets or sets an accessor property whose handler is debuggee code, or because the referent is a proxy whose traps are debuggee code), the call throws a [`Debugger.DebuggeeWouldRun`][wouldrun] exception. These methods may throw if the referent is not a native object. Even simple accessors like `isExtensible` may throw if the referent is a proxy or some sort of exotic object like an opaque wrapper. ### `getProperty(key, [receiver])` Return a [completion value][cv] with "return" being the value of the referent's property named key, or `undefined` if it has no such property. key must be a string or symbol; receiver must be a debuggee value. If the property is a getter, it will be evaluated with receiver as the receiver, defaulting to the `Debugger.Object` if omitted. All extant handler methods, breakpoints, and so on remain active during the call. ### `setProperty(key, value<, [receiver])` Store value as the value of the referent's property named key, creating the property if it does not exist. key must be a string or symbol; value and receiver must be debuggee values. If the property is a setter, it will be evaluated with receiver as the receiver, defaulting to the `Debugger.Object` if omitted. Return a [completion value][cv] with "return" being a success/failure boolean, or else "throw" being the exception thrown during property assignment. All extant handler methods, breakpoints, and so on remain active during the call. ### `getOwnPropertyDescriptor(key)` Return a property descriptor for the property named key of the referent. If the referent has no such property, return `undefined`. (This function behaves like the standard `Object.getOwnPropertyDescriptor` function, except that the object being inspected is implicit; the property descriptor returned is allocated as if by code scoped to the debugger's global object (and is thus in the debugger's compartment); and its `value`, `get`, and `set` properties, if present, are debuggee values.) ### `getOwnPropertyNames()` Return an array of strings naming all the referent's own properties, as if Object.getOwnPropertyNames(referent) had been called in the debuggee, and the result copied in the scope of the debugger's global object. ### `getOwnPropertyNamesLength()` Return the number of the referent's own properties. ### `getOwnPropertySymbols()` Return an array of strings naming all the referent's own symbols, as if Object.getOwnPropertySymbols(referent) had been called in the debuggee, and the result copied in the scope of the debugger's global object. ### `defineProperty(key, attributes)` Define a property on the referent named key, as described by the property descriptor descriptor. Any `value`, `get`, and `set` properties of attributes must be debuggee values. (This function behaves like `Object.defineProperty`, except that the target object is implicit, and in a different compartment from the function and descriptor.) ### `defineProperties(properties)` Add the properties given by properties to the referent. (This function behaves like `Object.defineProperties`, except that the target object is implicit, and in a different compartment from the properties argument.) ### `deleteProperty(key)` Remove the referent's property named key. Return true if the property was successfully removed, or if the referent has no such property. Return false if the property is non-configurable. ### `seal()` Prevent properties from being added to or deleted from the referent. Return this `Debugger.Object` instance. (This function behaves like the standard `Object.seal` function, except that the object to be sealed is implicit and in a different compartment from the caller.) ### `freeze()` Prevent properties from being added to or deleted from the referent, and mark each property as non-writable. Return this `Debugger.Object` instance. (This function behaves like the standard `Object.freeze` function, except that the object to be sealed is implicit and in a different compartment from the caller.) ### `preventExtensions()` Prevent properties from being added to the referent. (This function behaves like the standard `Object.preventExtensions` function, except that the object to operate on is implicit and in a different compartment from the caller.) ### `isSealed()` Return true if the referent is sealed—that is, if it is not extensible, and all its properties have been marked as non-configurable. (This function behaves like the standard `Object.isSealed` function, except that the object inspected is implicit and in a different compartment from the caller.) ### `isFrozen()` Return true if the referent is frozen—that is, if it is not extensible, and all its properties have been marked as non-configurable and read-only. (This function behaves like the standard `Object.isFrozen` function, except that the object inspected is implicit and in a different compartment from the caller.) ### `isExtensible()` Return true if the referent is extensible—that is, if it can have new properties defined on it. (This function behaves like the standard `Object.isExtensible` function, except that the object inspected is implicit and in a different compartment from the caller.) ### `makeDebuggeeValue(value)` Return the debuggee value that represents value in the debuggee. If value is a primitive, we return it unchanged; if value is an object, we return the `Debugger.Object` instance representing that object, wrapped appropriately for use in this `Debugger.Object`'s referent's compartment. Note that, if value is an object, it need not be one allocated in a debuggee global, nor even a debuggee compartment; it can be any object the debugger wishes to use as a debuggee value. As described above, each `Debugger.Object` instance presents its referent as viewed from a particular compartment. Given a `Debugger.Object` instance d and an object o, the call d.makeDebuggeeValue(o) returns a `Debugger.Object` instance that presents o as it would be seen by code in d's compartment. ### `isSameNative(value)` If value is a native function in the debugger's compartment, return whether the referent is a native function for the same C++ native. ### `isSameNativeWithJitInfo(value)` If value is a native function in the debugger's compartment, return whether the referent is a native function for the same C++ native with the same JSJitInfo pointer value. This can be used to distinguish functions with shared native function implementation with different JSJitInfo pointer to define the underlying functionality. ### `isNativeGetterWithJitInfo()` Return whether the referent is a native getter function with JSJitInfo. ### `decompile([pretty])` If the referent is a function that is debuggee code, return the JavaScript source code for a function definition equivalent to the referent function in its effect and result, as a string. If pretty is present and `true`, produce indented code with line breaks. If the referent is not a function that is debuggee code, return `undefined`. ### `call(this, argument, ...)` If the referent is callable, call it with the given this value and argument values, and return a [completion value][cv] describing how the call completed. This should be a debuggee value, or `{ asConstructor: true }` to invoke the referent as a constructor, in which case SpiderMonkey provides an appropriate `this` value itself. Each argument must be a debuggee value. All extant handler methods, breakpoints, and so on remain active during the call. If the referent is not callable, throw a `TypeError`. This function follows the [invocation function conventions][inv fr]. Note: If this method is called on an object whose owner [Debugger object][debugger-object] has an onNativeCall handler, only hooks on objects associated with that debugger will be called during the evaluation. ### `apply(this, arguments)` If the referent is callable, call it with the given this value and the argument values in arguments, and return a [completion value][cv] describing how the call completed. This should be a debuggee value, or `{ asConstructor: true }` to invoke function as a constructor, in which case SpiderMonkey provides an appropriate `this` value itself. Arguments must either be an array (in the debugger) of debuggee values, or `null` or `undefined`, which are treated as an empty array. All extant handler methods, breakpoints, and so on remain active during the call. If the referent is not callable, throw a `TypeError`. This function follows the [invocation function conventions][inv fr]. Note: If this method is called on an object whose owner [Debugger object][debugger-object] has an onNativeCall handler, only hooks on objects associated with that debugger will be called during the evaluation. ### `executeInGlobal(code, [options])` If the referent is a global object, evaluate code in that global environment, and return a [completion value][cv] describing how it completed. Code is a string. All extant handler methods, breakpoints, and so on remain active during the call (pending note below). This function follows the [invocation function conventions][inv fr]. If the referent is not a global object, throw a `TypeError` exception. Code is interpreted as strict mode code when it contains a Use Strict Directive. This evaluation is semantically equivalent to executing statements at the global level, not an indirect eval. Regardless of code being strict mode code, variable declarations in code affect the referent global object. The options argument is as for [`Debugger.Frame.prototype.eval`][fr eval]. Note: If this method is called on an object whose owner [Debugger object][debugger-object] has an onNativeCall handler, only hooks on objects associated with that debugger will be called during the evaluation. ### `executeInGlobalWithBindings(code, bindings, [options])` Like `executeInGlobal`, but evaluate code using the referent as the variable object, but with a lexical environment extended with bindings from the object bindings. An extra environment is created with bindings specified by bindings. The environment contains bindings corresponding to each own enumerable property of bindings, where the property name name as binding name, and the property value value as binding's initial value. If `options.useInnerBindings` is not specified or is specified as `false`, it emulates where the bindings environment is placed outside of global, which means, if the binding conflicts with any global variable declared in the code, or any existing global variable, the binding is ignored. If `options.useInnerBindings` is speified as `true`, it directly performs as the bindings environment is placed inside the global, and the provided bindings shadow the global variables. Each value must be a debuggee value. This is not like a `with` statement: code may access, assign to, and delete the introduced bindings without having any effect on the passed bindings object, because the properties are copied to a new object for each invocation. This method allows debugger code to introduce temporary bindings that are visible to the given debuggee code and which refer to debugger-held debuggee values, and do so without mutating any existing debuggee environment. Note that, like `executeInGlobal`, any declarations it contains affect the referent global object, even as code is evaluated in an environment extended according to bindings. (In the terms used by the ECMAScript specification, the `VariableEnvironment` of the execution context for code is the referent, and the bindings appear in a new declarative environment, which is the eval code's `LexicalEnvironment`.) The options argument is as for [`Debugger.Frame.prototype.eval`][fr eval]. Note: If this method is called on an object whose owner [Debugger object][debugger-object] has an onNativeCall handler, only hooks on objects associated with that debugger will be called during the evaluation. ### `createSource(options)` If the referent is a global object, return a new JavaScript source in the global's realm which has its properties filled in according to the `options` object. If the referent is not a global object, throw a `TypeError` exception. The `options` object can have the following properties: * `text`: String contents of the JavaScript in the source. * `url`: URL the resulting source should be associated with. * `startLine`: Starting line of the source. * `startColumn`: Starting column of the source. * `sourceMapURL`: Optional URL specifying the source's source map URL. If not specified, the source map URL can be filled in if specified by the source's text. * `isScriptElement`: Optional boolean which will set the source's `introductionType` to `"inlineScript"` if specified. Otherwise, the source's `introductionType` will be `undefined`. ### `asEnvironment()` If the referent is a global object, return the [`Debugger.Environment`][environment] instance representing the referent's global lexical scope. The global lexical scope's enclosing scope is the global object. If the referent is not a global object, throw a `TypeError`. ### `unwrap()` If the referent is a wrapper that this `Debugger.Object`'s compartment is permitted to unwrap, return a `Debugger.Object` instance referring to the wrapped object. If we are not permitted to unwrap the referent, return `null`. If the referent is not a wrapper, return this `Debugger.Object` instance unchanged. ### `unsafeDereference()` Return the referent of this `Debugger.Object` instance. If the referent is an inner object (say, an HTML5 `Window` object), return the corresponding outer object (say, the HTML5 `WindowProxy` object). This makes `unsafeDereference` more useful in producing values appropriate for direct use by debuggee code, without using [invocation functions][inv fr]. This method pierces the membrane of `Debugger.Object` instances meant to protect debugger code from debuggee code, and allows debugger code to access debuggee objects through the standard cross-compartment wrappers, rather than via `Debugger.Object`'s reflection-oriented interfaces. This method makes it easier to gradually adapt large code bases to this Debugger API: adapted portions of the code can use `Debugger.Object` instances, but use this method to pass direct object references to code that has not yet been updated. ### `forceLexicalInitializationByName(binding)` If binding is in an uninitialized state initialize it to undefined and return true, otherwise do nothing and return false. ### `getPromiseReactions` If the referent is a [`Promise`][promise] or a cross-compartment wrapper of one, this returns an array of objects describing the reaction records added to the promise. There are several different sorts of reaction records: - The array entry for a reaction record added with `then` or `catch` has the form `{ resolve: F, reject: F, result: P }`, where each `F` is a `Debugger.Object` referring to a function object, and `P` is the promise that will be resolved with the result of calling them. The `resolve` and `reject` properties may be absent in some cases. A call to `then` can omit the rejection handler, and a call to `catch` omits the resolution handler. Furthermore, various promise facilities create records like this as internal implementation details, creating handlers that are not representable as JavaScript functions. - When a promise `P1` is resolved to another promise `P2` (such that resolving `P2` resolves `P1` in the same way) that adds a reaction record to `P2`. The array entry for that reaction record is simply the `Debugger.Object` representing `P1`. Note that, if `P1` and `P2` are in different compartments, resolving `P1` to `P2` creates the same sort of reaction record as a call to `then` or `catch`, with `P1` stored only in a private slot of the `resolve` and `reject` functions, and not directly available from the reaction record. - An `await` expression calls `PromiseResolve` on its operand to obtain a promise `P`, and then adds a reaction record to `P` that resumes the suspended call appropriately. The array entry for that reaction record is a `Debugger.Frame` representing the suspended call. If the `await`'s operand `A` is a native promise with the standard constructor, then `PromiseResolve` simply returns `A` unchanged, and the reaction record for resuming the suspended call is added to `A`'s list. But if `A` is some other sort of 'thenable', then `PromiseResolve` creates a new promise and enqueues a job to call `A`'s `then` method; this may produce more indirect chains from awaitees to awaiters. - `JS::AddPromiseReactions` and `JS::AddPromiseReactionsIgnoringUnhandledRejection` create a reaction record whose promise field is `null`. [debugger-object]: Debugger.md [script]: Debugger.Script.md [environment]: Debugger.Environment.md [promise]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise [saved-frame]: ../SavedFrame/index [tracking-allocs]: Debugger.Memory.md#trackingallocationsites [inv fr]: Debugger.Frame.md#invocation-functions-and-debugger-frames [wouldrun]: Conventions.md#the-debugger-debuggeewouldrun-exception [cv]: Conventions.md#completion-values [fr eval]: Debugger.Frame.md#eval-code-options