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vm: sync-ify SourceTextModule linkage · nodejs/node@2086f33 · GitHub

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vm: sync-ify SourceTextModule linkage
Split `module.link(linker)` into two synchronous step `sourceTextModule.linkRequests()` and `sourceTextModule.instantiate()`. This allows creating vm modules and resolving the dependencies in a complete synchronous procedure. This also makes `syntheticModule.link()` redundant. The link step for a SyntheticModule is no-op and is already taken care in the constructor by initializing the binding slots with the given export names. PR-URL: #59000 Refs: #37648 Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
1 parent c8d6b60 commit 2086f33

16 files changed

Lines changed: 602 additions & 101 deletions

‎doc/api/errors.md‎

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@@ -2285,6 +2285,13 @@ The V8 platform used by this instance of Node.js does not support creating
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Workers. This is caused by lack of embedder support for Workers. In particular,
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this error will not occur with standard builds of Node.js.
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<a id="ERR_MODULE_LINK_MISMATCH"></a>
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### `ERR_MODULE_LINK_MISMATCH`
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A module can not be linked because the same module requests in it are not
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resolved to the same module.
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22882295
<a id="ERR_MODULE_NOT_FOUND"></a>
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22902297
### `ERR_MODULE_NOT_FOUND`

‎doc/api/vm.md‎

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@@ -419,9 +419,7 @@ class that closely mirrors [Module Record][]s as defined in the ECMAScript
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specification.
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421421
Unlike `vm.Script` however, every `vm.Module` object is bound to a context from
422-
its creation. Operations on `vm.Module` objects are intrinsically asynchronous,
423-
in contrast with the synchronous nature of `vm.Script` objects. The use of
424-
'async' functions can help with manipulating `vm.Module` objects.
422+
its creation.
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426424
Using a `vm.Module` object requires three distinct steps: creation/parsing,
427425
linking, and evaluation. These three steps are illustrated in the following
@@ -449,7 +447,7 @@ const contextifiedObject = vm.createContext({
449447
// Here, we attempt to obtain the default export from the module "foo", and
450448
// put it into local binding "secret".
451449

452-
const bar = new vm.SourceTextModule(`
450+
const rootModule = new vm.SourceTextModule(`
453451
import s from 'foo';
454452
s;
455453
print(s);
@@ -459,47 +457,56 @@ const bar = new vm.SourceTextModule(`
459457
//
460458
// "Link" the imported dependencies of this Module to it.
461459
//
462-
// The provided linking callback (the "linker") accepts two arguments: the
463-
// parent module (`bar` in this case) and the string that is the specifier of
464-
// the imported module. The callback is expected to return a Module that
465-
// corresponds to the provided specifier, with certain requirements documented
466-
// in `module.link()`.
467-
//
468-
// If linking has not started for the returned Module, the same linker
469-
// callback will be called on the returned Module.
460+
// Obtain the requested dependencies of a SourceTextModule by
461+
// `sourceTextModule.moduleRequests` and resolve them.
470462
//
471463
// Even top-level Modules without dependencies must be explicitly linked. The
472-
// callback provided would never be called, however.
473-
//
474-
// The link() method returns a Promise that will be resolved when all the
475-
// Promises returned by the linker resolve.
464+
// array passed to `sourceTextModule.linkRequests(modules)` can be
465+
// empty, however.
476466
//
477-
// Note: This is a contrived example in that the linker function creates a new
478-
// "foo" module every time it is called. In a full-fledged module system, a
479-
// cache would probably be used to avoid duplicated modules.
480-
481-
async function linker(specifier, referencingModule) {
482-
if (specifier === 'foo') {
483-
return new vm.SourceTextModule(`
484-
// The "secret" variable refers to the global variable we added to
485-
// "contextifiedObject" when creating the context.
486-
export default secret;
487-
`, { context: referencingModule.context });
488-
489-
// Using `contextifiedObject` instead of `referencingModule.context`
490-
// here would work as well.
491-
}
492-
throw new Error(`Unable to resolve dependency: ${specifier}`);
467+
// Note: This is a contrived example in that the resolveAndLinkDependencies
468+
// creates a new "foo" module every time it is called. In a full-fledged
469+
// module system, a cache would probably be used to avoid duplicated modules.
470+
471+
const moduleMap = new Map([
472+
['root', rootModule],
473+
]);
474+
475+
function resolveAndLinkDependencies(module) {
476+
const requestedModules = module.moduleRequests.map((request) => {
477+
// In a full-fledged module system, the resolveAndLinkDependencies would
478+
// resolve the module with the module cache key `[specifier, attributes]`.
479+
// In this example, we just use the specifier as the key.
480+
const specifier = request.specifier;
481+
482+
let requestedModule = moduleMap.get(specifier);
483+
if (requestedModule === undefined) {
484+
requestedModule = new vm.SourceTextModule(`
485+
// The "secret" variable refers to the global variable we added to
486+
// "contextifiedObject" when creating the context.
487+
export default secret;
488+
`, { context: referencingModule.context });
489+
moduleMap.set(specifier, linkedModule);
490+
// Resolve the dependencies of the new module as well.
491+
resolveAndLinkDependencies(requestedModule);
492+
}
493+
494+
return requestedModule;
495+
});
496+
497+
module.linkRequests(requestedModules);
493498
}
494-
await bar.link(linker);
499+
500+
resolveAndLinkDependencies(rootModule);
501+
rootModule.instantiate();
495502

496503
// Step 3
497504
//
498505
// Evaluate the Module. The evaluate() method returns a promise which will
499506
// resolve after the module has finished evaluating.
500507

501508
// Prints 42.
502-
await bar.evaluate();
509+
await rootModule.evaluate();
503510
```
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505512
```cjs
@@ -521,7 +528,7 @@ const contextifiedObject = vm.createContext({
521528
// Here, we attempt to obtain the default export from the module "foo", and
522529
// put it into local binding "secret".
523530

524-
const bar = new vm.SourceTextModule(`
531+
const rootModule = new vm.SourceTextModule(`
525532
import s from 'foo';
526533
s;
527534
print(s);
@@ -531,47 +538,56 @@ const contextifiedObject = vm.createContext({
531538
//
532539
// "Link" the imported dependencies of this Module to it.
533540
//
534-
// The provided linking callback (the "linker") accepts two arguments: the
535-
// parent module (`bar` in this case) and the string that is the specifier of
536-
// the imported module. The callback is expected to return a Module that
537-
// corresponds to the provided specifier, with certain requirements documented
538-
// in `module.link()`.
539-
//
540-
// If linking has not started for the returned Module, the same linker
541-
// callback will be called on the returned Module.
541+
// Obtain the requested dependencies of a SourceTextModule by
542+
// `sourceTextModule.moduleRequests` and resolve them.
542543
//
543544
// Even top-level Modules without dependencies must be explicitly linked. The
544-
// callback provided would never be called, however.
545-
//
546-
// The link() method returns a Promise that will be resolved when all the
547-
// Promises returned by the linker resolve.
545+
// array passed to `sourceTextModule.linkRequests(modules)` can be
546+
// empty, however.
548547
//
549-
// Note: This is a contrived example in that the linker function creates a new
550-
// "foo" module every time it is called. In a full-fledged module system, a
551-
// cache would probably be used to avoid duplicated modules.
552-
553-
async function linker(specifier, referencingModule) {
554-
if (specifier === 'foo') {
555-
return new vm.SourceTextModule(`
556-
// The "secret" variable refers to the global variable we added to
557-
// "contextifiedObject" when creating the context.
558-
export default secret;
559-
`, { context: referencingModule.context });
548+
// Note: This is a contrived example in that the resolveAndLinkDependencies
549+
// creates a new "foo" module every time it is called. In a full-fledged
550+
// module system, a cache would probably be used to avoid duplicated modules.
551+
552+
const moduleMap = new Map([
553+
['root', rootModule],
554+
]);
555+
556+
function resolveAndLinkDependencies(module) {
557+
const requestedModules = module.moduleRequests.map((request) => {
558+
// In a full-fledged module system, the resolveAndLinkDependencies would
559+
// resolve the module with the module cache key `[specifier, attributes]`.
560+
// In this example, we just use the specifier as the key.
561+
const specifier = request.specifier;
562+
563+
let requestedModule = moduleMap.get(specifier);
564+
if (requestedModule === undefined) {
565+
requestedModule = new vm.SourceTextModule(`
566+
// The "secret" variable refers to the global variable we added to
567+
// "contextifiedObject" when creating the context.
568+
export default secret;
569+
`, { context: referencingModule.context });
570+
moduleMap.set(specifier, linkedModule);
571+
// Resolve the dependencies of the new module as well.
572+
resolveAndLinkDependencies(requestedModule);
573+
}
574+
575+
return requestedModule;
576+
});
560577

561-
// Using `contextifiedObject` instead of `referencingModule.context`
562-
// here would work as well.
563-
}
564-
throw new Error(`Unable to resolve dependency: ${specifier}`);
578+
module.linkRequests(requestedModules);
565579
}
566-
await bar.link(linker);
580+
581+
resolveAndLinkDependencies(rootModule);
582+
rootModule.instantiate();
567583

568584
// Step 3
569585
//
570586
// Evaluate the Module. The evaluate() method returns a promise which will
571587
// resolve after the module has finished evaluating.
572588

573589
// Prints 42.
574-
await bar.evaluate();
590+
await rootModule.evaluate();
575591
})();
576592
```
577593

@@ -660,6 +676,10 @@ changes:
660676
Link module dependencies. This method must be called before evaluation, and
661677
can only be called once per module.
662678

679+
Use [`sourceTextModule.linkRequests(modules)`][] and
680+
[`sourceTextModule.instantiate()`][] to link modules either synchronously or
681+
asynchronously.
682+
663683
The function is expected to return a `Module` object or a `Promise` that
664684
eventually resolves to a `Module` object. The returned `Module` must satisfy the
665685
following two invariants:
@@ -805,8 +825,9 @@ const module = new vm.SourceTextModule(
805825
meta.prop = {};
806826
},
807827
});
808-
// Since module has no dependencies, the linker function will never be called.
809-
await module.link(() => {});
828+
// The module has an empty `moduleRequests` array.
829+
module.linkRequests([]);
830+
module.instantiate();
810831
await module.evaluate();
811832
812833
// Now, Object.prototype.secret will be equal to 42.
@@ -832,8 +853,9 @@ const contextifiedObject = vm.createContext({ secret: 42 });
832853
meta.prop = {};
833854
},
834855
});
835-
// Since module has no dependencies, the linker function will never be called.
836-
await module.link(() => {});
856+
// The module has an empty `moduleRequests` array.
857+
module.linkRequests([]);
858+
module.instantiate();
837859
await module.evaluate();
838860
// Now, Object.prototype.secret will be equal to 42.
839861
//
@@ -898,6 +920,69 @@ to disallow any changes to it.
898920
Corresponds to the `[[RequestedModules]]` field of [Cyclic Module Record][]s in
899921
the ECMAScript specification.
900922
923+
### `sourceTextModule.instantiate()`
924+
925+
<!-- YAML
926+
added: REPLACEME
927+
-->
928+
929+
* Returns: {undefined}
930+
931+
Instantiate the module with the linked requested modules.
932+
933+
This resolves the imported bindings of the module, including re-exported
934+
binding names. When there are any bindings that cannot be resolved,
935+
an error would be thrown synchronously.
936+
937+
If the requested modules include cyclic dependencies, the
938+
[`sourceTextModule.linkRequests(modules)`][] method must be called on all
939+
modules in the cycle before calling this method.
940+
941+
### `sourceTextModule.linkRequests(modules)`
942+
943+
<!-- YAML
944+
added: REPLACEME
945+
-->
946+
947+
* `modules` {vm.Module\[]} Array of `vm.Module` objects that this module depends on.
948+
The order of the modules in the array is the order of
949+
[`sourceTextModule.moduleRequests`][].
950+
* Returns: {undefined}
951+
952+
Link module dependencies. This method must be called before evaluation, and
953+
can only be called once per module.
954+
955+
The order of the module instances in the `modules` array should correspond to the order of
956+
[`sourceTextModule.moduleRequests`][] being resolved. If two module requests have the same
957+
specifier and import attributes, they must be resolved with the same module instance or an
958+
`ERR_MODULE_LINK_MISMATCH` would be thrown. For example, when linking requests for this
959+
module:
960+
961+
<!-- eslint-disable no-duplicate-imports -->
962+
963+
```mjs
964+
import foo from 'foo';
965+
import source Foo from 'foo';
966+
```
967+
968+
<!-- eslint-enable no-duplicate-imports -->
969+
970+
The `modules` array must contain two references to the same instance, because the two
971+
module requests are identical but in two phases.
972+
973+
If the module has no dependencies, the `modules` array can be empty.
974+
975+
Users can use `sourceTextModule.moduleRequests` to implement the host-defined
976+
[HostLoadImportedModule][] abstract operation in the ECMAScript specification,
977+
and using `sourceTextModule.linkRequests()` to invoke specification defined
978+
[FinishLoadingImportedModule][], on the module with all dependencies in a batch.
979+
980+
It's up to the creator of the `SourceTextModule` to determine if the resolution
981+
of the dependencies is synchronous or asynchronous.
982+
983+
After each module in the `modules` array is linked, call
984+
[`sourceTextModule.instantiate()`][].
985+
901986
### `sourceTextModule.moduleRequests`
902987

903988
<!-- YAML
@@ -1017,14 +1102,17 @@ the module to access information outside the specified `context`. Use
10171102
added:
10181103
- v13.0.0
10191104
- v12.16.0
1105+
changes:
1106+
- version: REPLACEME
1107+
pr-url: https://github.com/nodejs/node/pull/59000
1108+
description: No longer need to call `syntheticModule.link()` before
1109+
calling this method.
10201110
-->
10211111

10221112
* `name` {string} Name of the export to set.
10231113
* `value` {any} The value to set the export to.
10241114

1025-
This method is used after the module is linked to set the values of exports. If
1026-
it is called before the module is linked, an [`ERR_VM_MODULE_STATUS`][] error
1027-
will be thrown.
1115+
This method sets the module export binding slots with the given value.
10281116

10291117
```mjs
10301118
import vm from 'node:vm';
@@ -1033,7 +1121,6 @@ const m = new vm.SyntheticModule(['x'], () => {
10331121
m.setExport('x', 1);
10341122
});
10351123
1036-
await m.link(() => {});
10371124
await m.evaluate();
10381125
10391126
assert.strictEqual(m.namespace.x, 1);
@@ -1045,7 +1132,6 @@ const vm = require('node:vm');
10451132
const m = new vm.SyntheticModule(['x'], () => {
10461133
m.setExport('x', 1);
10471134
});
1048-
await m.link(() => {});
10491135
await m.evaluate();
10501136
assert.strictEqual(m.namespace.x, 1);
10511137
})();
@@ -2037,7 +2123,9 @@ const { Script, SyntheticModule } = require('node:vm');
20372123
[Cyclic Module Record]: https://tc39.es/ecma262/#sec-cyclic-module-records
20382124
[ECMAScript Module Loader]: esm.md#modules-ecmascript-modules
20392125
[Evaluate() concrete method]: https://tc39.es/ecma262/#sec-moduleevaluation
2126+
[FinishLoadingImportedModule]: https://tc39.es/ecma262/#sec-FinishLoadingImportedModule
20402127
[GetModuleNamespace]: https://tc39.es/ecma262/#sec-getmodulenamespace
2128+
[HostLoadImportedModule]: https://tc39.es/ecma262/#sec-HostLoadImportedModule
20412129
[HostResolveImportedModule]: https://tc39.es/ecma262/#sec-hostresolveimportedmodule
20422130
[ImportDeclaration]: https://tc39.es/ecma262/#prod-ImportDeclaration
20432131
[Link() concrete method]: https://tc39.es/ecma262/#sec-moduledeclarationlinking
@@ -2049,13 +2137,14 @@ const { Script, SyntheticModule } = require('node:vm');
20492137
[WithClause]: https://tc39.es/ecma262/#prod-WithClause
20502138
[`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING_FLAG`]: errors.md#err_vm_dynamic_import_callback_missing_flag
20512139
[`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`]: errors.md#err_vm_dynamic_import_callback_missing
2052-
[`ERR_VM_MODULE_STATUS`]: errors.md#err_vm_module_status
20532140
[`Error`]: errors.md#class-error
20542141
[`URL`]: url.md#class-url
20552142
[`eval()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval
20562143
[`optionsExpression`]: https://tc39.es/proposal-import-attributes/#sec-evaluate-import-call
20572144
[`script.runInContext()`]: #scriptrunincontextcontextifiedobject-options
20582145
[`script.runInThisContext()`]: #scriptruninthiscontextoptions
2146+
[`sourceTextModule.instantiate()`]: #sourcetextmoduleinstantiate
2147+
[`sourceTextModule.linkRequests(modules)`]: #sourcetextmodulelinkrequestsmodules
20592148
[`sourceTextModule.moduleRequests`]: #sourcetextmodulemodulerequests
20602149
[`url.origin`]: url.md#urlorigin
20612150
[`vm.compileFunction()`]: #vmcompilefunctioncode-params-options

‎lib/internal/bootstrap/realm.js‎

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Original file line numberDiff line numberDiff line change
@@ -359,6 +359,7 @@ class BuiltinModule {
359359
this.setExport('default', builtin.exports);
360360
});
361361
// Ensure immediate sync execution to capture exports now
362+
this.module.link([]);
362363
this.module.instantiate();
363364
this.module.evaluate(-1, false);
364365
return this.module;

‎lib/internal/errors.js‎

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Original file line numberDiff line numberDiff line change
@@ -1589,6 +1589,7 @@ E('ERR_MISSING_ARGS',
15891589
return `${msg} must be specified`;
15901590
}, TypeError);
15911591
E('ERR_MISSING_OPTION', '%s is required', TypeError);
1592+
E('ERR_MODULE_LINK_MISMATCH', '%s', TypeError);
15921593
E('ERR_MODULE_NOT_FOUND', function(path, base, exactUrl) {
15931594
if (exactUrl) {
15941595
lazyInternalUtil().setOwnProperty(this, 'url', `${exactUrl}`);

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