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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: Intl.MessageFormat
stage: 1
contributors: Eemeli Aro
</pre>
<emu-clause id="messageformat-objects">
<h1>MessageFormat Objects</h1>
<emu-clause id="sec-intl-messageformat-constructor">
<h1>The Intl.MessageFormat Constructor</h1>
<p>
The MessageFormat constructor is the <dfn>%MessageFormat%</dfn> intrinsic object
and a standard built-in property of the Intl object.
Behaviour common to all service constructor properties of the Intl object
is specified in <a href="https://tc39.es/ecma402/#sec-internal-slots">9.1</a>.
</p>
<emu-clause id="sec-intl.messageformat">
<h1>Intl.MessageFormat ( _source_, [ _locales_ [ , _options_ ] ] )</h1>
<p>
When the `Intl.MessageFormat` function is called with arguments
_source_, _locales_, and _options_, the following steps are taken:
</p>
<emu-alg>
1. If NewTarget is *undefined*, throw a *TypeError* exception.
1. Let _messageFormat_ be ? OrdinaryCreateFromConstructor(NewTarget, %MessageFormat.prototype%,
« [[InitializedMessageFormat]], [[LocaleMatcher]], [[MessageData]], [[RequestedLocales]], [[Runtime]] »).
1. Return ? InitializeMessageFormat(_messageFormat_, _source_, _locales_, _options_).
</emu-alg>
</emu-clause>
<emu-clause id="sec-initializemessageformat" aoid="InitializeMessageFormat">
<h1>InitializeMessageFormat ( _messageFormat_, _source_, _locales_, _options_ )</h1>
<p>
The abstract operation InitializeMessageFormat accepts the arguments
_messageFormat_ (which must be an object), _source_, _locales_, and _options_.
It initializes _messageFormat_ as a MessageFormat object.
The following steps are taken:
</p>
<emu-alg>
1. If _source_ is *undefined*, throw a *TypeError* exception.
1. Let _msgData_ be ? GetMessageData(_source_).
1. Let _requestedLocales_ be ? CanonicalizeLocaleList(_locales_).
1. Set _options_ to ? GetOptionsObject(_options_).
1. Let _matcher_ be ? GetOption(_options_, *"localeMatcher"*, ~string~,
« *"lookup"*, *"best fit"* », *"best fit"*).
1. Let _userFunctions_ be ? Get(_options_, *"functions"*).
1. Let _functions_ be ? GetMessageFunctions(_userFunctions_).
1. Set _messageFormat_.[[MessageData]] to _msgData_.
1. Set _messageFormat_.[[RequestedLocales]] to _requestedLocales_.
1. Set _messageFormat_.[[LocaleMatcher]] to _matcher_.
1. Set _messageFormat_.[[Functions]] to _functions_.
1. Return _messageFormat_.
</emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="sec-properties-of-intl-messageformat-constructor">
<h1>Properties of the Intl.MessageFormat Constructor</h1>
<p>
The Intl.MessageFormat constructor has the following properties:
</p>
<emu-clause id="sec-intl.messageformat.prototype">
<h1>Intl.MessageFormat.prototype</h1>
<p>
The value of `Intl.MessageFormat.prototype` is %MessageFormat.prototype%.
</p>
<p>
This property has the attributes
{ [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *false* }.
</p>
</emu-clause>
<emu-clause id="sec-intl.messageformat-internal-slots">
<h1>Internal slots</h1>
<emu-note>
Unlike other Intl formatters,
MessageFormat does not have a single list of locales that it supports,
as it calls other formatters as necessary.
</emu-note>
</emu-clause>
</emu-clause>
<emu-clause id="sec-properties-of-intl-messageformat-prototype-object">
<h1>Properties of the Intl.MessageFormat Prototype Object</h1>
<p>
The Intl.MessageFormat prototype object is itself an ordinary object.
<dfn>%MessageFormat.prototype%</dfn> is not an Intl.MessageFormat instance
and does not have an [[InitializedMessageFormat]] internal slot
or any of the other internal slots of Intl.MessageFormat instance objects.
</p>
<emu-clause id="sec-intl.messageformat.prototype.constructor">
<h1>Intl.MessageFormat.prototype.constructor</h1>
<p>
The initial value of `Intl.MessageFormat.prototype.constructor` is %MessageFormat%.
</p>
</emu-clause>
<emu-clause id="sec-intl.messageformat.prototype-tostringtag">
<h1>Intl.MessageFormat.prototype [ @@toStringTag ]</h1>
<p>
The initial value of the @@toStringTag property is the String value *"Intl.MessageFormat"*.
</p>
<p>
This property has the attributes
{ [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.
</p>
</emu-clause>
<emu-clause id="sec-intl.messageformat.prototype.format">
<h1>Intl.MessageFormat.prototype.format ( [ _values_ [ , _onError_ ] ] )</h1>
<p>
When the `format` method is called with the optional arguments
_values_ and _onError_, the following steps are taken:
</p>
<emu-alg>
1. Let _mf_ be the *this* value.
1. Perform ? RequireInternalSlot(_mf_, [[InitializedMessageFormat]]).
1. Let _ctx_ be ? CreateMessageFormatContext(_mf_, _values_, _onError_).
1. Let _msg_ be ? ResolveMessage(_ctx_).
1. Let _result_ be an empty String.
1. For each element _el_ of _msg_, do
1. If Type(_el_) is String, then
1. Let _stringValue_ be _el_.
1. Else if Type(_el_) is Object and _el_ has a [[MessageValue]] internal slot, then
1. Let _mv_ be _el_.[[MessageValue]].
1. Assert: Type(_mv_) is Object.
1. Let _toString_ be ? Get(_mv_, *"toString"*).
1. Let _toStringResult_ be Completion(Call(_toString_, _mv_)).
1. If _toStringResult_ is a normal completion, then
1. Let _stringValue_ be _toStringResult_.[[Value]].
1. Else,
1. Perform ? HandleMessageFormatError(_ctx_, _stringResult_).
1. Let _source_ be MessageValueSource(_mv_).
1. Let _stringValue_ be MessageFallbackString(_source_).
1. Set _result_ to the string-concatenation of _result_ and _stringValue_.
1. Return _result_.
</emu-alg>
</emu-clause>
<emu-clause id="sec-intl.messageformat.prototype.formatToParts">
<h1>Intl.MessageFormat.prototype.formatToParts ( [ _values_ [ , _onError_ ] ] )</h1>
<p>
When the `formatToParts` method is called with the optional arguments
_values_ and _onError_, the following steps are taken:
</p>
<emu-alg>
1. Let _mf_ be the *this* value.
1. Perform ? RequireInternalSlot(_mf_, [[InitializedMessageFormat]]).
1. Let _ctx_ be ? CreateMessageFormatContext(_mf_, _values_, _onError_).
1. Let _msg_ be ? ResolveMessage(_ctx_).
1. Let _result_ be a new empty List.
1. For each element _mv_ of _msg_, do
1. If Type(_mv_) is String, then
1. Let _textPart_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_textPart_, *"type"*, *"text"*).
1. Perform ! CreateDataPropertyOrThrow(_textPart_, *"value"*, _el_).
1. Append _textPart_ to _result_.
1. Else if Type(_el_) is Object and _el_ has a [[MessageMarkup]] internal slot, then
1. Let _markup_ be ? FormatMarkupPart(_ctx_, _el_.[[MessageMarkup]]).
1. Append _markup_ to _result_
1. Else,
1. Assert: _el_ has a [[MessageValue]] internal slot.
1. Let _mv_ be _el_.[[MessageValue]].
1. Assert: Type(_mv_) is Object.
1. Let _toParts_ be ? Get(_mv_, *"toParts"*).
1. Let _partResult_ be Completion(Call(_toParts_, _mv_)).
1. If _partResult_ is a normal completion, then
1. Let _parts_ be _partResult_.[[Value]].
1. For each element _part_ of _parts_, append _part_ to _result_.
1. Else,
1. Perform ? HandleMessageFormatError(_ctx_, _partResult_).
1. Let _source_ be MessageValueSource(_mv_).
1. Let _fallbackPart_ be MessageFallbackPart(_source_).
1. Append _fallbackPart_ to _result_.
1. Return CreateArrayFromList(_result_).
</emu-alg>
</emu-clause>
<emu-clause id="sec-intl.messageformat.prototype.resolvedoptions">
<h1>Intl.MessageFormat.prototype.resolvedOptions ( )</h1>
<p>
This function provides access to the locale and options
computed during initialization of the object.
</p>
<emu-alg>
1. Let _mf_ be the *this* value.
1. Perform ? RequireInternalSlot(_mf_, [[InitializedMessageFormat]]).
1. Let _options_ be OrdinaryObjectCreate(%Object.prototype%).
1. For each row of <emu-xref href="#table-messageformat-resolvedoptions-properties"></emu-xref>,
except the header row, in table order, do
1. Let _p_ be the Property value of the current row.
1. Let _v_ be the value of _mf_'s internal slot
whose name is the Internal Slot value of the current row.
1. If _v_ is not *undefined*, then
1. Perform ! CreateDataPropertyOrThrow(_options_, _p_, _v_).
1. Return _options_.
</emu-alg>
<emu-table id="table-messageformat-resolvedoptions-properties">
<emu-caption>Resolved Options of MessageFormat Instances</emu-caption>
<table class="real-table">
<thead>
<tr>
<th>Internal Slot</th>
<th>Property</th>
</tr>
</thead>
<tr>
<td>[[Functions]]</td>
<td>*"functions"*</td>
</tr>
<tr>
<td>[[LocaleMatcher]]</td>
<td>*"localeMatcher"*</td>
</tr>
<tr>
<td>[[RequestedLocales]]</td>
<td>*"locales"*</td>
</tr>
<tr>
<td>[[MessageData]]</td>
<td>*"message"*</td>
</tr>
</table>
</emu-table>
</emu-clause>
</emu-clause>
<emu-clause id="sec-properties-of-intl-messageformat-instances">
<h1>Properties of Intl.MessageFormat Instances</h1>
<p>
Intl.MessageFormat instances are ordinary objects that inherit properties from %MessageFormat.prototype%.
</p>
<p>
Intl.MessageFormat instances have an [[InitializedMessageFormat]] internal slot.
</p>
<p>
Intl.MessageFormat instances also have several internal slots that are computed by the constructor:
</p>
<ul>
<li>
[[LocaleMatcher]] is one of the String values *"lookup"* or *"best fit"*,
identifying the locale matcher used.
</li>
<li>
[[MessageData]] is an Object conforming to the
<a href="https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model/message.json">JSON Schema definition</a>
of the Unicode MessageFormat 2.0 specification.
</li>
<li>
[[RequestedLocales]] is a List of String values
with the canonicalized language tags of the requested locales
to use for message formatting.
</li>
<li>[[Functions]] is an Object with function object values.</li>
</ul>
</emu-clause>
<emu-clause id="sec-intl-messageformat-abstracts">
<h1>Abstract Operations for MessageFormat Objects</h1>
<emu-clause id="sec-getmessagedata" type="implementation-defined abstract operation">
<h1>
GetMessageData (
_source_: a String or an Object,
): an Object conforming to the <a href="https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model/message.json">JSON Schema definition</a> of a message according to the Unicode MessageFormat 2.0 specification
</h1>
<dl class="header">
<dt>description</dt>
<dd>
<p>
If _source_ is a String, it returns the message data representation corresponding to the input _source_ according to the
<a href="https://github.com/unicode-org/message-format-wg/blob/main/spec/syntax.md">Unicode MessageFormat 2.0 syntax</a>.
If _source_ is an Object, it checks that _source_ holds a valid message data representation,
and returns an equivalent Object that is not affected by any further changes to _source_.
</p>
<p>If _source_ contains a syntax or data model error, this operation throws a *SyntaxError*.</p>
</dd>
</dl>
</emu-clause>
<emu-clause id="sec-getmessagefunctions" type="abstract operation">
<h1>
GetMessageFunctions (
_userFunctions_: an Object or undefined,
): an Object
</h1>
<dl class="header">
<dt>description</dt>
<dd>It determines the functions available during message formatting.</dd>
</dl>
<emu-alg>
1. Let _numberSteps_ be the algorithm steps defined in <emu-xref href="#sec-messageformat-numberfunctions"></emu-xref>.
1. Let _number_ be CreateBuiltinFunction(_numberSteps_, *3*, *"number"*, « »).
1. Let _stringSteps_ be the algorithm steps defined in <emu-xref href="#sec-messageformat-stringfunctions"></emu-xref>.
1. Let _string_ be CreateBuiltinFunction(_stringSteps_, *3*, *"string"*, « »).
1. Let _dateTimeSteps_ be the algorithm steps defined in <emu-xref href="#sec-messageformat-stringfunctions"></emu-xref>.
1. Let _dateTime_ be CreateBuiltinFunction(_dateTimeSteps_, *3*, *"string"*, « »).
1. Let _functions_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_functions_, *"number"*, _number_).
1. Perform ! CreateDataPropertyOrThrow(_functions_, *"string"*, _string_).
1. Perform ! CreateDataPropertyOrThrow(_functions_, *"datetime"*, _dateTime_).
1. For each String _name_ of ? EnumerableOwnProperties(_userFunctions_, ~key~),
1. Let _func_ be ? Get(_userFunctions_, _name_).
1. If IsCallable(_func_) is *true*, then
1. Perform ! CreateDataPropertyOrThrow(_functions_, _name_, _func_).
1. Else,
1. Throw a *TypeError* exception.
1. Return _functions_.
</emu-alg>
<emu-clause id="sec-messageformat-numberfunctions">
<h1>MessageFormat Number Functions</h1>
<p>
A MessageFormat number function is an anonymous built-in function.
</p>
<p>
When a MessageFormat number function is called with arguments _funcCtx_ (an Object), _options_ (an Object), and _input_ (an ECMAScript language value), the following steps are taken:
</p>
<emu-alg>
1. Let _locale_ be ! Get(_funcCtx_, *"locale"*).
1. Let _localeMatcher_ be ! Get(_funcCtx_, *"localeMatcher"*).
1. Let _source_ be ! Get(_funcCtx_, *"source"*).
1. Let _opts_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_opt_, *"localeMatcher"*, _localeMatcher_).
1. If Type(_input_) is String, then
1. Set _input_ to ? Call(JSON.parse, %JSON%, « _input_ »).
1. Else if Type(_input_) is Object, then
1. Let _valueOf_ be ? Get(_input_, *"valueOf"*).
1. If IsCallable(_valueOf_) is *true*, then
1. Let _inputOptions_ be ? Get(_input_, *"options"*).
1. Perform ? Call(Object.assign, *undefined*, « _opts_, _inputOptions_ »).
1. Set _input_ to ? Call(_valueOf_, _input_).
1. If Type(_input_) is not Number or BigInt, throw a *TypeError* exception.
1. Let _numberOptions_ be « *"minimumIntegerDigits"*, *"minimumFractionDigits"*, *"maximumFractionDigits"*, *"minimumSignificantDigits"*, *"maximumSignificantDigits"*, *"roundingIncrement"* ».
1. Let _booleanOptions_ be « *"useGrouping"* ».
1. Let _select_ be *"cardinal"*.
1. For each String _optName_ of ? EnumerableOwnProperties(_options_, ~key~),
1. If _optName_ is not *"localeMatcher"* and _optName_ is not *"type"*, then <!-- TODO: Fix bad indent -->
1. Let _optValue_ be ? Get(_options_, _optName_).
1. If Type(_optValue_) is Object, then
1. Let _optValueOf_ be ? Get(_optValue_, *"valueOf"*).
1. If IsCallable(_optValueOf_) is *true*, then
1. Set _optValue_ to ? Call(_optValueOf_, _optValue_).
1. If _optName_ is *"select"*, then
1. If _optValue_ is *"ordinal"* or _optValue_ is *"exact"*, then
1. Set _select_ to _optValue_
1. Else if _optValue_ is not *"plural"*, then
1. Throw a *RangeError* exception.
1. Else,
1. If Type(_optValue_) is String, then
1. If _numberOptions_ contains _optName_, then
1. Set _optValue_ to ToNumber(_optValue_).
1. Else if _booleanOptions_ contains _optName_, then
1. If _optValue_ is *"true"*, then
1. Set _optValue_ to *true*.
1. Else if _optValue_ is *"false"*, then
1. Set _optValue_ to *false*.
1. Perform ? Set(_opts_, _optName_, _optValue_, *true*).
1. Let _numberFormat_ be ? Construct(%Intl.NumberFormat%, « _locale_, _opts_ »).
1. If _select_ is *"exact"*, then
1. Perform ? _opts_.[[Delete]](*"type"*).
1. Let _pluralRules_ be *undefined*.
1. Else,
1. Perform ? Set(_opts_, *"type"*, _select_, *true*).
1. Let _pluralRules_ be ? Construct(%Intl.PluralRules%, « _locale_, _opts_ »).
1. Let _selectKeyClosure_ be a new Abstract Closure with parameters (_keys_) that captures _input_ and _pluralRules_ and performs the following steps when called:
1. Let _keyList_ be ? CreateListFromArrayLike(_keys_, « String »).
1. Let _str_ be ? ToString(_input_).
1. If _keyList_ contains _str_, return _str_.
1. If _pluralRules_ is not *undefined*, then
1. Let _category_ be ? Call(Intl.PluralRules.prototype.select, _pluralRules_, « _input_ »).
1. If _keyList_ contains _category_, return _category_.
1. Return *null*.
1. Let _selectKey_ be CreateBuiltinFunction(_selectKeyClosure_, *1*, *"selectKey"*, « »).
1. Let _toPartsClosure_ be a new Abstract Closure with no parameters that captures _input_, _source_, and _numberFormat_ and performs the following steps when called:
1. Let _parts_ be ? Call(Intl.NumberFormat.prototype.formatToParts, _numberFormat_, « _input_ »).
1. Let _result_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"type"*, *"number"*).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"locale"*, _numberFormat_.[[Locale]]).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"parts"*, _parts_).
1. Return CreateArrayFromList(« _result_ »).
1. Let _toParts_ be CreateBuiltinFunction(_toPartsClosure_, *0*, *"toParts"*, « »).
1. Let _toStringClosure_ be a new Abstract Closure with no parameters that captures _input_ and _numberFormat_ and performs the following steps when called:
1. Return ? Call(Intl.NumberFormat.prototype.format, _numberFormat_, « _input_ »).
1. Let _toString_ be CreateBuiltinFunction(_toStringClosure_, *0*, *"toString"*, « »).
1. Let _valueOfClosure_ be a new Abstract Closure with no parameters that captures _input_ and performs the following steps when called:
1. Return _input_.
1. Let _valueOf_ be CreateBuiltinFunction(_valueOfClosure_, *0*, *"valueOf"*, « »).
1. Let _mv_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"type"*, *"number"*).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"locale"*, _numberFormat_.[[Locale]]).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"options"*, _opts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"selectKey"*, _selectKey_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toParts"*, _toParts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toString"*, _toString_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"valueOf"*, _valueOf_).
1. Return _mv_.
</emu-alg>
<p>
The *"length"* property of a MessageFormat number function is *3*.
</p>
</emu-clause>
<emu-clause id="sec-messageformat-stringfunctions">
<h1>MessageFormat String Functions</h1>
<p>
A MessageFormat string function is an anonymous built-in function.
</p>
<p>
When a MessageFormat string function is called with arguments _funcCtx_ (an Object), _options_ (an Object), and _input_ (an ECMAScript language value), the following steps are taken:
</p>
<emu-alg>
1. Let _str_ be ? ToString(_input_).
1. Let _selectKeyClosure_ be a new Abstract Closure with parameters (_keys_) that captures _str_ and performs the following steps when called:
1. Let _keyList_ be ? CreateListFromArrayLike(_keys_, « String »).
1. If _keyList_ contains _str_, return _str_.
1. Else, return *null*.
1. Let _selectKey_ be CreateBuiltinFunction(_selectKeyClosure_, *1*, *"selectKey"*, « »).
1. Let _toPartsClosure_ be a new Abstract Closure with no parameters that captures _funcCtx_ and _str_ and performs the following steps when called:
1. Let _source_ be ! Get(_funcCtx_, *"source"*).
1. Let _locale_ be ! Get(_funcCtx_, *"locale"*).
1. Let _locale0_ be ! Get(_locale_, *"0"*).
1. Let _result_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"type"*, *"string"*).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"locale"*, _locale0_).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"value"*, _str_).
1. Return CreateArrayFromList(« _result_ »).
1. Let _toParts_ be CreateBuiltinFunction(_toPartsClosure_, *0*, *"toParts"*, « »).
1. Let _toStringClosure_ be a new Abstract Closure with no parameters that captures _str_ and performs the following steps when called:
1. Return _str_.
1. Let _toString_ be CreateBuiltinFunction(_toStringClosure_, *0*, *"toString"*, « »).
1. Let _valueOf_ be CreateBuiltinFunction(_toStringClosure_, *0*, *"valueOf"*, « »).
1. Let _mv_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"type"*, *"number"*).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"locale"*, _numberFormat_.[[Locale]]).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"options"*, _opts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"selectKey"*, _selectKey_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toParts"*, _toParts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toString"*, _toString_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"valueOf"*, _valueOf_).
1. Return _mv_.
</emu-alg>
<p>
The *"length"* property of a MessageFormat string function is *3*.
</p>
</emu-clause>
<emu-clause id="sec-messageformat-datetimefunctions">
<h1>MessageFormat DateTime Functions</h1>
<p>
A MessageFormat dateTime function is an anonymous built-in function.
</p>
<p>
When a MessageFormat dateTime function is called with arguments _funcCtx_ (an Object), _options_ (an Object), and _input_ (an ECMAScript language value), the following steps are taken:
</p>
<emu-alg>
1. Let _locale_ be ! Get(_funcCtx_, *"locale"*).
1. Let _localeMatcher_ be ! Get(_funcCtx_, *"localeMatcher"*).
1. Let _source_ be ! Get(_funcCtx_, *"source"*).
1. Let _opts_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_opt_, *"localeMatcher"*, _localeMatcher_).
1. If Type(_input_) is Object, then
1. If HasProperty(_input_, *"options"*) is *true*, then
1. Let _inputOptions_ be ? Get(_input_, *"options"*).
1. Perform ? Call(Object.assign, *undefined*, « _opts_, _inputOptions_ »).
1. Let _valueOf_ be ? Get(_input_, *"valueOf"*).
1. If InstanceOfOperator(_input_, %Date%) is *false* and IsCallable(_valueOf_) is *true*, set _input_ to Call(_valueOf_, _input_).
1. If Type(_input_) is Number or String, let _value_ be ? Construct(%Date%, « _input_ »).
1. Else if Type(_input_) is Object, let _value_ be _input_.
1. If InstanceOfOperator(_value_, %Date%) is *false*, throw a *TypeError* exception.
1. For each String _optName_ of ? EnumerableOwnProperties(_options_, ~key~),
1. If _optName_ is not *"locale"*, then
1. Let _optValue_ be ? Get(_options_, _optName_).
1. If Type(_optValue_) is Object, then
1. Let _optValueOf_ be ? Get(_optValue_, *"valueOf"*).
1. If IsCallable(_optValueOf_) is *true*, then
1. Set _optValue__ to ? Call(_optValueOf_, _optValue_).
1. If _optName_ is *"fractionalSecondDigits"*, set _optValue_ to ToNumber(_optValue_).
1. Else if _optName_ is *"hour12"*, then
1. If _optValue_ is *"true"*, then
1. Set _optValue_ to *true*.
1. Else if _optValue_ is *"false"*, then
1. Set _optValue_ to *false*.
1. Else, set _optValue_ to ToString(_optValue_).
1. Perform ? Set(_opts_, _optName_, _optValue_, *"true"*).
1. Let _dateTimeFormat_ be ? Construct(%Intl.DateTimeFormat%, « _locale_, _opts_ »).
1. Let _toPartsClosure_ be a new Abstract Closure with no parameters that captures _value_, _source_, and _dateTimeFormat_ and performs the following steps when called:
1. Let _parts_ be ? Call(Intl.DateTimeFormat.prototype.formatToParts, _dateTimeFormat_, « _value_ »).
1. Let _result_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"type"*, *"datetime"*).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"locale"*, _dateTimeFormat_.[[Locale]]).
1. Perform ! CreateDataPropertyOrThrow(_result_, *"parts"*, _parts_).
1. Return CreateArrayFromList(« _result_ »).
1. Let _toParts_ be CreateBuiltinFunction(_toPartsClosure_, *0*, *"toParts"*, « »).
1. Let _toStringClosure_ be a new Abstract Closure with no parameters that captures _value_ and _dateTimeFormat_ and performs the following steps when called:
1. Return ? Call(Intl.DateTimeFormat.prototype.format, _dateTimeFormat_, « _value_ »).
1. Let _toString_ be CreateBuiltinFunction(_toStringClosure_, *0*, *"toString"*, « »).
1. Let _valueOfClosure_ be a new Abstract Closure with no parameters that captures _value_ and performs the following steps when called:
1. Return _value_.
1. Let _valueOf_ be CreateBuiltinFunction(_valueOfClosure_, *0*, *"valueOf"*, « »).
1. Let _mv_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"type"*, *"datetime"*).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"locale"*, _dateTimeFormat_.[[Locale]]).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"options"*, _opts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toParts"*, _toParts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toString"*, _toString_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"valueOf"*, _valueOf_).
1. Return _mv_.
</emu-alg>
<p>
The *"length"* property of a MessageFormat number function is *3*.
</p>
</emu-clause>
</emu-clause>
<emu-clause id="sec-createmessageformatcontext" type="abstract operation">
<h1>
CreateMessageFormatContext (
_mf_: an Object,
_values_: an Object or undefined,
_onError_: a Function or undefined
): a MessageFormatContext Record
</h1>
<dl class="header">
<dt>description</dt>
<dd>It initializes the MessageFormatContext Record used for pattern selection and formatting.</dd>
</dl>
<emu-alg>
1. Let _localVars_ be OrdinaryObjectCreate(*null*).
1. Let _msgData_ be _mf_.[[MessageData]].
1. Let _declArray_ be ? Get(_msgData_, *"declarations"*).
1. Let _declList_ be ? CreateListFromArrayLike(_declArray_).
1. For each element _decl_ of _declList_,
1. Let _declName_ be ? Get(_decl_, *"name"*).
1. Let _declValue_ be OrdinaryObjectCreate(*null*, « [[UnresolvedDeclaration]] »).
1. Set _declValue_.[[UnresolvedDeclaration]] to _decl_.
1. Perform ? Set(_localVars_, _declName_, _declValue_, *true*).
1. Let _ctx_ be a new Record.
1. Set _ctx_.[[LocalVariables]] to _localVars_.
1. Set _ctx_.[[MessageFormat]] to _mf_.
1. Set _ctx_.[[OnError]] to _onError_.
1. Set _ctx_.[[Values]] to ? GetOptionsObject(_values_).
1. Return _ctx_.
</emu-alg>
<emu-clause id="sec-messagecontextrecord">
<h1>MessageFormatContext Records</h1>
<p>
A <dfn id="messageformatcontext-record">MessageFormatContext Record</dfn> is used to hold the data required during the formatting of a message.
It has the fields defined in <emu-xref href="#table-messageformatcontext-record"></emu-xref>.
</p>
<emu-table id="table-messageformatcontext-record">
<emu-caption>Record returned by CreateMessageContext</emu-caption>
<table class="real-table">
<thead>
<tr>
<th>Field Name</th>
<th>Value Type</th>
<th>Description</th>
</tr>
</thead>
<tr>
<td>[[LocalVariables]]</td>
<td>Object</td>
<td>
Cache for local variables, which may be resolved during the formatting.
The values in the cache are Objects, each of which will have either [[MessageValue]], [[ResolvedValue]], or [[UnresolvedDeclaration]] internal slots.
</td>
</tr>
<tr>
<td>[[MessageFormat]]</td>
<td>Intl.MessageFormat</td>
<td>The MessageFormat instance on which the formatting is taking place.</td>
</tr>
<tr>
<td>[[OnError]]</td>
<td>Function object or *undefined*.</td>
<td>The _onError_ argument of the formatter call.</td>
</tr>
<tr>
<td>[[Values]]</td>
<td>Object</td>
<td>The _values_ argument of the formatter call.</td>
</tr>
</table>
</emu-table>
</emu-clause>
</emu-clause>
<emu-clause id="sec-resolvemessage" type="abstract operation">
<h1>
ResolveMessage (
_ctx_: a MessageFormatContext Record
): a List of Strings and Objects
</h1>
<dl class="header">
<dt>description</dt>
<dd>It resolves a message into a List of Strings and Objects with either [[MessageMarkup]] or [[MessageValue]] internal slots.</dd>
</dl>
<emu-alg>
1. Let _result_ be an empty List.
1. Let _pattern_ be ? SelectPattern(_ctx_).
1. For each element _el_ of _pattern_,
1. If Type(_el_) is String, then
1. Append _el_ to _result_.
1. Else,
1. Assert: Type(_el_) is Object.
1. Let _elType_ be ? Get(_el_, *"type"*).
1. If _elType_ is *"markup"*, then
1. Let _res_ be OrdinaryObjectCreate(*null*, « [[MessageMarkup]] »).
1. Set _res_.[[MessageMarkup]] to _el_.
1. Else,
1. Assert: _elType_ is *"expression"*.
1. Let _res_ be ResolveExpression(_ctx_, _el_).
1. Append _res_ to _result_.
1. Return _result_.
</emu-alg>
<emu-clause id="sec-selectpattern" type="abstract operation">
<h1>
SelectPattern (
_ctx_: a MessageFormatContext Record
): a List of Strings and Objects with an internal slot [[MessageValue]]
</h1>
<dl class="header">
<dt>description</dt>
<dd>It selects the pattern to format from the message data model.</dd>
</dl>
<emu-alg>
1. Let _msgData_ be _ctx_.[[MessageFormat]].[[MessageData]].
1. Let _msgType_ be ? Get(_msgData_, *"type"*).
1. If _msgType_ is *"message"*, then
1. Let _pattern_ be ? Get(_msgData_, *"pattern"*).
1. Else,
1. Assert: _msgType_ is *"select"*.
1. Let _selectorsData_ be ? Get(_msgData_, *"selectors"*).
1. Let _selectorExpressions_ be ? CreateListFromArrayLike(_selectorsData_, « Object »).
1. Let _selectors_ be an empty List.
1. For each element _selExp_ of _selectorExpressions_,
1. Let _sel_ be ResolveExpression(_ctx_, _selExp_).
1. Let _selectKey_ be ? Get(_sel_.[[MessageValue]], *"selectKey"*).
1. If IsCallable(_selectKey_) is *true*, then
1. Append _sel_.[[MessageValue]] to _selectors_.
1. Else,
1. Let _error_ be ThrowCompletion(*TypeError*).
1. Perform ? HandleMessageFormatError(_ctx_, _error_).
1. Append *null* to _selectors_.
1. Let _variantsArray_ be ? Get(_msgData_, *"variants"*).
1. Let _variants_ be ? CreateListFromArrayLike(_variantsArray_, « Object »).
1. Let _selectedVariant_ be ? SelectVariant(_ctx_, _selectors_, _variants_).
1. Return ? CreateListFromArrayLike(_pattern_, « String, Object »).
</emu-alg>
</emu-clause>
<emu-clause id="sec-selectvariant" type="implementation-defined abstract operation">
<h1>
SelectVariant (
_ctx_: a MessageFormatContext Record,
_selectors_: a List of Object and Null values,
_variants_: a List of Objects
): an Object
</h1>
<dl class="header">
<dt>description</dt>
<dd>
<p>
It applies the variant selection method defined by
the "Resolve Preferences", "Filter Variants", and "Sort Variants" steps of the
<a href="https://github.com/unicode-org/message-format-wg/blob/main/spec/formatting.md#pattern-selection">Pattern Selection</a>
section of the Unicode MessageFormat 2.0 specification.
</p>
<p>
For the selection, Null values in _selectors_ indicate selectors for which selection will always fail.
If any errors are encountered during the selection,
the HandleMessageFormatError abstract operation must be called
with _ctx_ and an abrupt Completion Record containing an Error.
</p>
<p>
The value returned by this operation must be an Object matching the JSON Schema definition of a message pattern:
<a href="https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model/message.json#/$defs/pattern">
https://github.com/unicode-org/message-format-wg/blob/main/spec/data-model/message.json#/$defs/pattern
</a>.
</p>
</dd>
</dl>
</emu-clause>
</emu-clause>
<emu-clause id="sec-resolveexpression" type="abstract operation">
<h1>
ResolveExpression (
_ctx_: a MessageFormatContext Record,
_expression_: an Object,
): an Object with an internal slot [[MessageValue]]
</h1>
<dl class="header">
<dt>description</dt>
<dd>It resolves the value of an expression for selection and formatting.</dd>
</dl>
<emu-alg>
1. Let _source_ be ? GetSource(_ctx_, _expression_).
1. Let _arg_ be ? Get(_expression_, *"arg"*).
1. If _arg_ is *undefined*, then
1. Let _resArg_ be *undefined*.
1. Else,
1. Let _resArg_ be ResolveValue(_ctx_, _arg_).
1. If _resArg_ has a [[MessageFallback]] internal slot, return _resArg_.
1. Let _annotation_ be ? Get(_expression_, *"annotation"*).
1. If _annotation_ is *undefined*, then
1. Assert: _resArg_ is not *undefined*.
1. If Type(_resArg_) is Object and _resArg_ has a [[MessageValue]] internal slot, then
1. Return _resArg_.
1. Else if Type(_resArg_) is Number or BigInt, then
1. Set _annotation_ to OrdinaryObjectCreate(*null*).
1. Perform ! CreateDataPropertyOrThrow(_annotation_, *"type"*, *"function"*).
1. Perform ! CreateDataPropertyOrThrow(_annotation_, *"name"*, *"number"*).
1. Else if Type(_resArg_) is String, then
1. Set _annotation_ to OrdinaryObjectCreate(*null*).
1. Perform ! CreateDataPropertyOrThrow(_annotation_, *"type"*, *"function"*).
1. Perform ! CreateDataPropertyOrThrow(_annotation_, *"name"*, *"string"*).
1. Else,
1. Return ResolveUnknown(_source_, _resArg_).
1. If ? Get(_annotation_, *"type"*) is not *"function"*, then
1. Let _error_ be ThrowCompletion(*ReferenceError*).
1. Perform ? HandleMessageFormatError(_ctx_, _error_).
1. Return ResolveFallback(_source_).
1. Return ResolveFunction(_ctx_, _source_, _resArg_, _annotation_).
</emu-alg>
<emu-clause id="sec-resolvefunction" type="abstract operation">
<h1>
ResolveFunction (
_ctx_: a MessageFormatContext Record,
_source_: a String,
_resArg_: an Object or undefined,
_annotation_: an Object,
): an Object with an internal slot [[MessageValue]]
</h1>
<dl class="header">
<dt>description</dt>
<dd>It resolves the value of an expression with a function annotation.</dd>
</dl>
<emu-alg>
1. Let _name_ be ? Get(_annotation_, *"name"*).
1. Let _function_ be ? Get(_ctx_.[[MessageFormat]].[[Functions]], _name_).
1. If IsCallable(_function_) is *false*, then
1. Let _error_ be ThrowCompletion(*ReferenceError*).
1. Perform ? HandleMessageFormatError(_ctx_, _error_).
1. Return ResolveFallback(_source_).
1. Let _funcCtx_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_funcCtx_, *"locale"*, _ctx_.[[MessageFormat]].[[RequestedLocales]]).
1. Perform ! CreateDataPropertyOrThrow(_funcCtx_, *"localeMatcher"*, _ctx_.[[MessageFormat]].[[LocaleMatcher]]).
1. Perform ! CreateDataPropertyOrThrow(_funcCtx_, *"source"*, _source_).
1. Let _options_ be OrdinaryObjectCreate(%Object.prototype%).
1. Let _optArray_ be ? Get(_annotation_, *"options"*).
1. If _optArray_ is not *undefined*, then
1. Let _optList_ be ? CreateListFromArrayLike(_optArray_).
1. For each element _opt_ of _optList_,
1. Let _optName_ be ? Get(_opt_, *"name"*).
1. Let _optValue_ be ? Get(_opt_, *"value"*).
1. Let _resValue_ be ResolveValue(_ctx_, _optValue_).
1. If Type(_resValue_) is Object, then
1. If _resValue_ has a [[MessageFallback]] internal slot, then
1. Set _resValue_ to *undefined*.
1. Else if _resValue_ has a [[MessageValue]] internal slot, then
1. Set _resValue_ to _resValue_.[[MessageValue]].
1. Perform ? CreateDataPropertyOrThrow(_options_, _optName_, _resValue_).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"options"*, _resOptions_).
1. Let _funcArgs_ be « _funcCtx_, _options_ ».
1. If Type(_resArg_) is Object and _resArg_ has a [[MessageValue]] internal slot, then
1. Set _resArg_ to _resArg_.[[MessageValue]].
1. If _resArg_ is not *undefined*, then
1. Append _resArg_ to _funcArgs_.
1. Let _funcRes_ be Completion(Call(_function_, *undefined*, _funcArgs_)).
1. If _funcRes_ is a normal completion, then
1. Let _mv_ be _funcRes_.[[Value]].
1. If Type(_mv_) is Object and Type(? Get(_mv_, *"type"*)) is String and Type(? Get(_mv_, *"source"*)) is String, then
1. Let _result_ be OrdinaryObjectCreate(*null*, « [[MessageValue]] »).
1. Set _result_.[[MessageValue]] to _mv_.
1. Return _result_.
1. Else,
1. Let _error_ be ThrowCompletion(*TypeError*).
1. Perform ? HandleMessageFormatError(_ctx_, _error_).
1. Return ResolveFallback(_source_).
1. Else,
1. Perform ? HandleMessageFormatError(_ctx_, _funcRes_).
1. Return ResolveFallback(_source_).
</emu-alg>
</emu-clause>
<emu-clause id="sec-resolveunknown" type="abstract operation">
<h1>
ResolveUnknown (
_source_: a String,
_value_: an ECMAScript language value
): an Object with an internal slot [[MessageValue]]
</h1>
<dl class="header">
<dt>description</dt>
<dd>It resolves an unknown value.</dd>
</dl>
<emu-alg>
1. Let _toPartsClosure_ be a new Abstract Closure with no parameters that captures _source_ and _value_ and performs the following steps when called:
1. Let _part_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"type"*, *"unknown"*).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"value"*, _value_).
1. Return CreateArrayFromList(« _part_ »).
1. Let _toParts_ be CreateBuiltinFunction(_toPartsClosure_, *0*, *"toParts"*, « »).
1. Let _toStringClosure_ be a new Abstract Closure with no parameters that captures _value_ and performs the following steps when called:
1. Return ? ToString(_value_).
1. Let _toString_ be CreateBuiltinFunction(_toStringClosure_, *0*, *"toString"*, « »).
1. Let _valueOfClosure_ be a new Abstract Closure with no parameters that captures _value_ and performs the following steps when called:
1. Return _value_.
1. Let _valueOf_ be CreateBuiltinFunction(_valueOfClosure_, *0*, *"valueOf"*, « »).
1. Let _mv_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"type"*, *"unknown"*).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"source"*, _source_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"locale"*, *"und"*).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toParts"*, _toParts_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"toString"*, _toString_).
1. Perform ! CreateDataPropertyOrThrow(_mv_, *"valueOf"*, _valueOf_).
1. Let _unknown_ be OrdinaryObjectCreate(*null*, « [[MessageValue]] »).
1. Set _unknown_.[[MessageValue]] to _mv_.
1. Return _unknown_.
</emu-alg>
</emu-clause>
</emu-clause>
<emu-clause id="sec-formatmarkuppart" type="abstract operation">
<h1>
FormatMarkupPart (
_ctx_: a MessageFormatContext Record,
_markup_: an Object,
): an Object
</h1>
<dl class="header">
<dt>description</dt>
<dd>It resolves the formatted part value of a markup placeholder.</dd>
</dl>
<emu-alg>
1. Let _kind_ be ? Get(_markup_, *"kind"*).
1. Let _name_ be ? Get(_markup_, *"name"*).
1. Let _options_ be ? Get(_markup_, *"options"*).
1. Let _part_ be OrdinaryObjectCreate(%Object.prototype%).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"type"*, *"markup"*).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"kind"*, _kind_).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"name"*, _name_).
1. If _kind_ is not *"close"* and _options_ is not *undefined*, then
1. Let _len_ be ? LengthOfArrayLike(_options_).
1. If _len_ > 0, then
1. Let _opts_ be ? CreateListFromArrayLike(_options_).
1. Let _resOptions_ be OrdinaryObjectCreate(%Object.prototype%).
1. For each element _opt_ of _opts_,
1. Let _optName_ be ? Get(_opt_, *"name"*).
1. Let _optValue_ be ? Get(_opt_, *"value"*).
1. Let _resValue_ be ResolveValue(_ctx_, _optValue_).
1. If Type(_resValue_) is Object, then
1. If _resValue_ has a [[MessageFallback]] internal slot, then
1. Set _resValue_ to *undefined*.
1. Else,
1. Let _valueOf_ be ? Get(_resValue_, *"valueOf"*).
1. If IsCallable(_valueOf_) is *true*, then
1. Let _valueOfResult_ be Completion(Call(_valueOf_, _resValue_)).
1. If _valueOfResult_ is a normal completion, then
1. Set _resValue_ to _valueOfResult_.[[Value]].
1. Else,
1. Perform ? HandleMessageFormatError(_ctx_, _valueOfResult_).
1. Set _resValue_ to *undefined*.
1. Perform ! CreateDataPropertyOrThrow(_resOptions_, _optName_, _resValue_).
1. Perform ! CreateDataPropertyOrThrow(_part_, *"options"*, _resOptions_).
1. Return CreateArrayFromList(« _part_ »).
</emu-alg>
</emu-clause>
<emu-clause id="sec-getsource" type="abstract operation">
<h1>
GetSource (
_ctx_: a MessageFormatContext Record,
_value_: an Object
): a String
</h1>
<dl class="header">
<dt>description</dt>
<dd>Determines the "source" value for a data model Object.</dd>
</dl>
<emu-alg>
1. Let _type_ be ? Get(_value_, *"type"*).
1. If _type_ is *"literal"*, then
1. Let _strValue_ be ? Get(_value_, *"value"*).
1. Modify _strValue_ such that all *"\"* characters are replaced with *"\\"*.
1. Modify _strValue_ such that all *"|"* characters are replaced with *"\|"*.
1. Return the string-concatenation of *"|"*, _strValue_, and *"|"*.
1. If _type_ is *"variable"*, then
1. Let _name_ be ? Get(_value_, *"name"*).
1. Let _local_ be ! Get(_ctx_.[[LocalVariables]], _name_).
1. If Type(_local_) is Object, then
1. If _local_ has an [[UnresolvedDeclaration]] internal slot, then
1. Let _decl_ be _local_.[[UnresolvedDeclaration]].
1. If ? Get(_decl_, *"type"*) is *"local"*, then
1. Let _declValue_ be ? Get(_decl_, *"value"*).
1. Return ? GetSource(_ctx_, _declValue_).
1. Else if _local_ has a [[MessageValue]] internal slot, then
1. Return MessageValueSource(_local_.[[MessageValue]]).
1. Else,
1. Assert: _local_ has a [[ResolvedName]] internal slot.
1. Assert: _local_ has a [[ResolvedValue]] internal slot.
1. Set _name_ to _local_.[[ResolvedName]].
1. Return the string-concatenation of *"$"* and _name_.
1. If _type_ is *"markup"*, then
1. Let _kind_ be ? Get(_value_, *"kind"*).
1. Let _name_ be ? Get(_value_, *"name"*).
1. If _kind_ is *"open"*, return the string-concatenation of *"#"* and _name_.
1. If _kind_ is *"standalone"*, return the string-concatenation of *"#"*, _name_, and *"/"*.
1. If _kind_ is *"close"*, return the string-concatenation of *"/"* and _name_.
1. If _type_ is *"function"*, then
1. Let _name_ be ? Get(_value_, *"name"*).
1. Return the string-concatenation of *":"* and _name_.
1. If _type_ is *"unsupported-annotation"*, then
1. Return ? Get(_value_, *"sigil"*).
1. If _type_ is *"expression"*, then
1. Let _arg_ be ? Get(_value_, *"arg"*).
1. If _arg_ is not *undefined*, return ? GetSource(_ctx_, _arg_).
1. Let _annotation_ be ? Get(_value_, *"annotation"*).
1. If _annotation_ is not *undefined*, return ? GetSource(_ctx_, _annotation_).
1. Return *"\uFFFD"*.
</emu-alg>
<emu-clause id="sec-messagevaluesource" type="abstract operation">
<h1>
MessageValueSource (
_mv_: an Object
): a String
</h1>
<dl class="header">
<dt>description</dt>
<dd>
It gets the source string representation of a resolved message value,
which should be always available.
On any error, it returns the Unicode replacement character � instead.
</dd>
</dl>
<emu-alg>