This proposal would ideally use the withkeyword to denote attributes, but there are existing implementations based on the previous version of the proposal using the assertkeyword. Due to potential web compatibility risks, the proposal still includes assert marked as normative optional and legacy in sections 13.3.10.2 and 16.2.2. Usage of the old syntax is discouraged, and it removal is being investigated.
+
This feature would ideally use the withkeyword to denote attributes, but there are existing implementations based on a previous version of the proposal using the assertkeyword. Due to potential web compatibility risks, the proposal still includes assert marked as deprecated. Usage of the old syntax is discouraged, and its removal is being investigated.
+
+
2 Conformance
+
+
A conforming implementation of ECMAScript should not implement Deprecated subclauses or algorithm steps, unless necessary for compatibility with existing applications that already run in such implementation before the deprecation of the given language feature. All of the language features and behaviours specified within Deprecated subclauses or algorithm steps have one or more undesirable characteristics. However, their use in existing applications currently prevents their removal from this specification. These features are not considered part of the core ECMAScript language. Programmers should not use or assume the existence of these features and behaviours when writing new ECMAScript code.
The abstract operation EvaluateImportCall takes argument specifierExpression (a ParseNode) and optional argument optionsExpression (a ParseNode) and returns either a normal completion containing a Promise or a throw completion. It performs the following steps when called:
Perform ! Call(promiseCapability.[[Reject]], undefined, « a newly created TypeError object »).
Return promiseCapability.[[Promise]].
Sort attributes according to the lexicographic order of their [[Key]] fields, treating the value of each such field as a sequence of UTF-16 code unit values. NOTE: This sorting is observable only in that hosts are prohibited from distinguishing among attributes by the order they occur in.
Let moduleRequest be a new ModuleRequest Record { [[Specifier]]: specifierString, [[Attributes]]: attributes }.
Perform ! Call(promiseCapability.[[Reject]], undefined, « a newly created TypeError object »).
Return promiseCapability.[[Promise]].
Sort attributes according to the lexicographic order of their [[Key]] fields, treating the value of each such field as a sequence of UTF-16 code unit values. NOTE: This sorting is observable only in that hosts are prohibited from distinguishing among attributes by the order they occur in.
Let moduleRequest be a new ModuleRequest Record { [[Specifier]]: specifierString, [[Attributes]]: attributes }.
If moduleNamesrequests does not contain name a ModuleRequest Recordmr2 such that mr.[[Specifer]] is mr2.[[Specifer]] and AttributesEqual(mr.[[Attributes]], mr2.[[Attributes]]) is true, then
If moduleNamesrequests does not contain name a ModuleRequest Recordmr2 such that mr.[[Specifer]] is mr2.[[Specifer]] and AttributesEqual(mr.[[Attributes]], mr2.[[Attributes]]) is true, then
A Cyclic Module Record is used to represent information about a module that can participate in dependency cycles with other modules that are subclasses of the Cyclic Module Record type. Module Records that are not subclasses of the Cyclic Module Record type must not participate in dependency cycles with Source Text Module Records.
A Cyclic Module Record is used to represent information about a module that can participate in dependency cycles with other modules that are subclasses of the Cyclic Module Record type. Module Records that are not subclasses of the Cyclic Module Record type must not participate in dependency cycles with Source Text Module Records.
A List of all the ModuleSpecifier strings and import attributes used by the module represented by this record to request the importation of a module. The List is in source text occurrence order.
@@ -3007,7 +2998,7 @@
A map from the specifier strings used by the module represented by this record to request the importation of a module with the relative attributes to the resolved Module Record. The list does not contain two different Records with the same [[Specifier]]([[Specifier]], [[Attributes]]) pair.
@@ -3062,8 +3053,8 @@
16.2.1.5 Cyclic Module Records
16.2.1.6 Source Text Module Records
-
An ImportEntry Record is a Record that digests information about a single declarative import. Each ImportEntry Record has the fields defined in Table 4:
An ImportEntry Record is a Record that digests information about a single declarative import. Each ImportEntry Record has the fields defined in Table 4:
If referrer.[[LoadedModules]] contains a Recordrecord such that record.[[Specifier]] is specifiermoduleRequest.[[Specifier]] and AttributesEqual(record.[[Attributes]], moduleRequest.[[Attributes]]) is true, then
Else, append the Record { [[Specifier]]: specifiermoduleRequest.[[Specifer]], [[Attributes]]: moduleRequest.[[Attributes]], [[Module]]: result.[[Value]] } to referrer.[[LoadedModules]].
If referrer.[[LoadedModules]] contains a Recordrecord such that record.[[Specifier]] is specifiermoduleRequest.[[Specifier]] and AttributesEqual(record.[[Attributes]], moduleRequest.[[Attributes]]) is true, then
Else, append the Record { [[Specifier]]: specifiermoduleRequest.[[Specifer]], [[Attributes]]: moduleRequest.[[Attributes]], [[Module]]: result.[[Value]] } to referrer.[[LoadedModules]].
The abstract operation AllImportAttributesSupported takes argument attributes (a List of ImportAttribute Records) and returns a Boolean. It performs the following steps when called:
If supported does not contain attribute.[[Key]], return false.
Return true.
+
The abstract operation AllImportAttributesSupported takes argument attributes (a List of ImportAttribute Records) and returns a Boolean. It performs the following steps when called:
Sort attributes according to the lexicographic order of their [[Key]] fields, treating the value of each such field as a sequence of UTF-16 code unit values. NOTE: This sorting is observable only in that hosts are prohibited from distinguishing among attributes by the order they occur in.
Sort attributes according to the lexicographic order of their [[Key]] fields, treating the value of each such field as a sequence of UTF-16 code unit values. NOTE: This sorting is observable only in that hosts are prohibited from distinguishing among attributes by the order they occur in.
16.2.2.4 Deprecated assert keyword for Import Attributes
+
+
Import Attributes are denoted using the withkeyword. However, there are existing implementations based on a previous version of the proposal using the assertkeyword. Due to potential web compatibility risks, the assertkeyword is still included in this specification, but its removal is being investigated.
+
+
This deprecated feature includes the assert fallback for import attributes in import calls (step 11.d of 13.3.10.2).
Sort attributes by the code point order of the [[Key]] of each element. NOTE: This sorting is observable only in that hosts are prohibited from distinguishing among attributes by the order they occur in.
The module script would have an additional item, which would be the module type, as a string (e.g., "json"), or undefined for a JavaScript module.
-
HostLoadImportedModule would take a ModuleRequest Record parameter in place of a specifier string, which would be passed down through several abstract operations to reach the fetch a single module script algorithm. Somewhere near the entrypoint, if the ModuleRequest Record's [[Attributes]] field has an element entry such that entry.[[Key]] is "type", then let type be entry.[[Value]]; otherwise let type be undefined. If the type is invalid, then an exception is thrown and module loading fails. Otherwise, this will equal the module type, if the module can be successfully fetched with a matching MIME type.
-
In the fetch the descendents of a module script algorithm, when iterating over [[RequestedModules]], the elements are ModuleRequest Records rather than just specifier strings; these Records is passed on to the internal module script graph fetching procedure (which sends it to "fetch a single module script". Other usage sites of [[RequestedModules]] ignore the attribute.
+
HostLoadImportedModule would take a ModuleRequest Record parameter in place of a specifier string, which would be passed down through several abstract operations to reach the fetch a single module script algorithm. Somewhere near the entrypoint, if the ModuleRequest Record's [[Attributes]] field has an element entry such that entry.[[Key]] is "type", then let type be entry.[[Value]]; otherwise let type be undefined. If the type is invalid, then an exception is thrown and module loading fails. Otherwise, this will equal the module type, if the module can be successfully fetched with a matching MIME type.
+
In the fetch the descendents of a module script algorithm, when iterating over [[RequestedModules]], the elements are ModuleRequest Records rather than just specifier strings; these Records is passed on to the internal module script graph fetching procedure (which sends it to "fetch a single module script". Other usage sites of [[RequestedModules]] ignore the attribute.
"Fetch a single module script" would check the attribute in two places:
The module map is keyed with both the absolute URL and the module type, so an existing entry will be found only if its type matches.
This proposal would ideally use the `with` keyword to denote attributes, but there are existing implementations based on the previous version of the proposal using the `assert` keyword. Due to potential web compatibility risks, the proposal still includes `assert` marked as normative optional and legacy in sections and . Usage of the old syntax is discouraged, and it removal is being investigated.
+
This feature would ideally use the `with` keyword to denote attributes, but there are existing implementations based on a previous version of the proposal using the `assert` keyword. Due to potential web compatibility risks, the proposal still includes `assert` marked as deprecated. Usage of the old syntax is discouraged, and its removal is being investigated.
+
+
Conformance
+
+
A conforming implementation of ECMAScript should not implement Deprecated subclauses or algorithm steps, unless necessary for compatibility with existing applications that already run in such implementation before the deprecation of the given language feature. All of the language features and behaviours specified within Deprecated subclauses or algorithm steps have one or more undesirable characteristics. However, their use in existing applications currently prevents their removal from this specification. These features are not considered part of the core ECMAScript language. Programmers should not use or assume the existence of these features and behaviours when writing new ECMAScript code.
+
+
+
Example Deprecated Clause Heading
+
Example clause contents.
+
+
+
ECMAScript Language: Expressions
@@ -121,7 +103,7 @@
1. Return _promiseCapability_.[[Promise]].
1. Let _attributesObj_ be Completion(Get(_options_, *"with"*)).
1. IfAbruptRejectPromise(_attributesObj_, _promiseCapability_).
- 1. [normative-optional-legacy=""] If _attributesObj_ is *undefined*, then
+ 1. [id="step-evaluate-import-call-assert-fallback", deprecated="", normative-optional=""] If the host supports the deprecated `assert` keyword for import attributes and _attributesObj_ is *undefined*, then
1. Let _attributesObj_ be Completion(Get(_options_, *"assert"*)).
1. IfAbruptRejectPromise(_attributesObj_, _promiseCapability_).
1. If _attributesObj_ is not *undefined*, then
@@ -145,6 +127,10 @@
1. Perform HostLoadImportedModule(_referrer_, _moduleRequest_, ~empty~, _promiseCapability_).
1. Return _promiseCapability_.[[Promise]].
+
+
+ Removal of the `assert` fallback when _options_'s `with` property is *undefined* is being investigated.
+
It is a Syntax Error if WithClauseToAttributes of |WithClause| has two entries _a_ and _b_ such that _a_.[[Key]] is _b_.[[Key]].
It is a Syntax Error if AllImportAttributesSupported(WithClauseToAttributes of |WithClause|) is *false*.
+
+
+
This section is extended by .
+
@@ -730,18 +718,14 @@
- WithClause :
- `with` `{` `}`
- `assert` `{` `}`
+ WithClause : `with` `{` `}`
1. Return a new empty List.
- WithClause :
- `with` `{` WithEntries `,`? `}`
- `assert` `{` WithEntries `,`? `}`
+ WithClause : `with` `{` WithEntries `,`? `}`
1. Let _attributes_ be WithClauseToAttributes of |WithEntries|.
@@ -763,6 +747,55 @@
1. Let _rest_ be WithClauseToAttributes of |WithEntries|.
1. Return the list-concatenation of « _entry_ » and _rest_.
+
+
+
This section is extended by .
+
+
+
+
+
Deprecated `assert` keyword for Import Attributes
+
+
Import Attributes are denoted using the `with` keyword. However, there are existing implementations based on a previous version of the proposal using the `assert` keyword. Due to potential web compatibility risks, the `assert` keyword is still included in this specification, but its removal is being investigated.
+
+
This deprecated feature includes the `assert` fallback for import attributes in import calls (step of ).
+
+
The following augments the |ImportDeclaration| production in :
It is a Syntax Error if WithClauseToAttributes of |AssertClause| has two entries _a_ and _b_ such that _a_.[[Key]] is _b_.[[Key]].
+
It is a Syntax Error if AllImportAttributesSupported(WithClauseToAttributes of |AssertClause|) is *false*.
+
+
+
The static semantics of WithClauseToAttributes in are augmented to include the following:
+
+ AssertClause : `assert` `{` `}`
+
+
+ 1. Return a new empty List.
+
+
+
+ AssertClause : `assert` `{` WithEntries `,`? `}`
+
+
+ 1. Let _attributes_ be WithClauseToAttributes of |WithEntries|.
+ 1. Sort _attributes_ by the code point order of the [[Key]] of each element. NOTE: This sorting is observable only in that hosts are prohibited from distinguishing among attributes by the order they occur in.
+ 1. Return _attributes_.
+