proposal-error-stack-accessor/spec.emu at main · tc39/proposal-error-stack-accessor · GitHub

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<!doctype html>
<meta charset="utf8">
<link rel="stylesheet" href="./spec.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/8.4/styles/github.min.css">
<script src="./spec.js"></script>
<pre class="metadata">
title: Error Stack Accessor
stage: 2
contributors: Jordan Harband, Mark Miller
</pre>

<emu-clause id="sec-fundamental-objects" number="20">
  <h1>Fundamental Objects</h1>

  <emu-clause id="sec-error-objects" number="5">
    <h1>Error Objects</h1>

    <emu-clause id="sec-properties-of-the-error-prototype-object" number="3">
      <h1>Properties of the Error Prototype Object</h1>

      <emu-clause id="sec-get-error.prototype-stack">
        <h1>Error.prototype.stack</h1>
        <p>`Error.prototype.stack` is an accessor property with attributes { [[Enumerable]]: *false*, [[Configurable]]: *true* }. The [[Get]] and [[Set]] attributes are defined as follows:</p>

        <emu-clause id="sec-get-error.prototype.stack">
          <h1>get Error.prototype.stack</h1>
          <p>The value of the [[Get]] attribute is a built-in function that requires no arguments. It performs the following steps when called:</p>
          <emu-alg>
            1. Let _E_ be the *this* value.
            1. If _E_ is not an Object, throw a *TypeError* exception.
            1. If _E_ does not have an [[ErrorData]] internal slot, return *undefined*.
            1. Return an implementation-defined string that represents the stack trace of _E_.
          </emu-alg>
        </emu-clause>

        <emu-clause id="sec-set-error.prototype.stack">
          <h1>set Error.prototype.stack</h1>
          <p>The value of the [[Set]] attribute is a built-in function that takes an argument _v_. It performs the following steps when called:</p>
          <emu-alg>
            1. Let _E_ be the *this* value.
            1. If _E_ is not an Object, throw a *TypeError* exception.
            1. If _v_ is not a String, throw a *TypeError* exception.
            1. Perform ? SetterThatIgnoresPrototypeProperties(*this* value, %Error.prototype%, *"stack"*, _v_).
            1. Return *undefined*.
          </emu-alg>
        </emu-clause>
      </emu-clause>
    </emu-clause>

    <emu-clause id="sec-properties-of-error-instances" number="4">
      <h1>Properties of Error Instances</h1>
      <p>Error instances are ordinary objects that inherit properties from the Error prototype object and have an [[ErrorData]] internal slot whose value is *undefined*. <del>The only specified use of [[ErrorData]] is by `Object.prototype.toString` (<emu-xref href="#sec-object.prototype.tostring"></emu-xref>) and `Error.isError` (<emu-xref href="#sec-error.iserror"></emu-xref>) to identify Error, AggregateError, or _NativeError_ instances.</del><ins>Specified uses of [[ErrorData]] include to identify <emu-xref href="#sec-error-constructor">Error</emu-xref>, <emu-xref href="#sec-aggregate-error-constructor">AggregateError</emu-xref>, and _NativeError_ instances as Error objects within `Object.prototype.toString` and `Error.isError`; as well as for the <emu-xref href="#sec-get-error.prototype-stack">Error.prototype.stack accessor</emu-xref>.</ins></p>
    </emu-clause>

    <emu-clause id="sec-nativeerror-object-structure" number="6">
      <h1>_NativeError_ Object Structure</h1>

      <emu-clause id="sec-properties-of-nativeerror-instances" number="4">
          <h1>Properties of _NativeError_ Instances</h1>
          <p>_NativeError_ instances are ordinary objects that inherit properties from their _NativeError_ prototype object and have an [[ErrorData]] internal slot whose value is *undefined*. <del>The only specified use of [[ErrorData]] is by `Object.prototype.toString` (<emu-xref href="#sec-object.prototype.tostring"></emu-xref>) and `Error.isError` (<emu-xref href="#sec-error.iserror"></emu-xref>) to identify Error, AggregateError, or _NativeError_ instances.</del><ins>Specified uses of [[ErrorData]] include to identify <emu-xref href="#sec-error-constructor">Error</emu-xref>, <emu-xref href="#sec-aggregate-error-constructor">AggregateError</emu-xref>, and _NativeError_ instances as Error objects within `Object.prototype.toString` and `Error.isError`; as well as for the <emu-xref href="#sec-get-error.prototype-stack">Error.prototype.stack accessor</emu-xref>.</ins></p>
      </emu-clause>
    </emu-clause>

    <emu-clause id="sec-aggregate-error-objects" number="7">
      <h1>AggregateError Objects</h1>

      <emu-clause id="sec-properties-of-aggregate-error-instances" number="4">
        <h1>Properties of AggregateError Instances</h1>
        <p>AggregateError instances are ordinary objects that inherit properties from their AggregateError prototype object and have an [[ErrorData]] internal slot whose value is *undefined*. <del>The only specified use of [[ErrorData]] is by `Object.prototype.toString` (<emu-xref href="#sec-object.prototype.tostring"></emu-xref>) and `Error.isError` (<emu-xref href="#sec-error.iserror"></emu-xref>) to identify Error, AggregateError, or _NativeError_ instances.</del><ins>Specified uses of [[ErrorData]] include to identify <emu-xref href="#sec-error-constructor">Error</emu-xref>, <emu-xref href="#sec-aggregate-error-constructor">AggregateError</emu-xref>, and _NativeError_ instances as Error objects within `Object.prototype.toString` and `Error.isError`; as well as for the <emu-xref href="#sec-get-error.prototype-stack">Error.prototype.stack accessor</emu-xref>.</ins></p>
      </emu-clause>
    </emu-clause>
  </emu-clause>
</emu-clause>