test262/test/language/module-code/instn-named-iee-cycle.js

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Module semantics: declaration instantiation Files whose name ends in `_.js` are not themselves valid Test262 tests and should not be interpreted as such by test runners. --- Because the tests in this patch concern declaration *instantiation*, care has been taken to avoid asserting binding values following evaluation. Because a given module's dependencies are evaluated prior to the module itself, this is only observable in modules which import their own bindings. A separate patch dedicated to the evaluation of module code asserts the behavior of bindings following evaluation. --- For tests that concern the creation of a module namespace object, this patch relies on the semantics of the `in` operator. The `in` operator uses the [[HasProperty]] internal method and avoids testing unrelated semantics concerning binding resolution. Those semantics should be explicitly asserted with a separate set of tests dedicated to that purpose. --- One test case which is notably missing is error resulting from a cycle due to an `import` declaration (under the current file naming scheme, such a test might be named `instn-named-err-circular.js`). Due to the recursive nature of ModuleDeclarationInstantiation, it is not technically possible for a circular request to be found in step 12.c.i. Cycles rely on at least 2 `export` declarations, and because these are resolved *before* imports, any cycle would trigger failure prior to step 12.c. --- One aspect of *module* resolution that makes ordering observable is the fact that resolution can fail in two distinct ways (i.e. with a SyntaxError or with a ReferenceError). This patch includes tests that leverage this detail in order to assert that modules are resolved in the correct sequence. However, from the perspective of the ECMA-262 specification, the ordering of *export* (e.g. binding) resolution is not observable. This is due to restrictions on the grammar, where each export is independent. When *export* resolution fails, it does so with instances of SyntaxError alone, precluding the above strategy. So while ModuleDeclarationInstantiation resolves the exports of the module's dependencies in the following order: 1. "Indirect" exports, e.g. - `export { x } from './y.js';` - `export { x as z } from './y.js';` - `import { x } from './y.js'; export { x };` 2. "Star" imports - `import * as ns from './y.js';` 3. "Named" (my word) imports - `import x from './y.js';` - `import { x } from './y.js';` - `import { x as z } from './y.js';` Intentional failures cannot be used to discern resolution ordering.
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// Copyright (C) 2016 the V8 project authors. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
description: >
There are no restrictions on the number of cycles during module traversal
during indirect export resolution, given unique export names.
esid: sec-moduledeclarationinstantiation
info: |
[...]
12. For each ImportEntry Record in in module.[[ImportEntries]], do
a. Let importedModule be ? HostResolveImportedModule(module,
in.[[ModuleRequest]]).
b. If in.[[ImportName]] is "*", then
[...]
c. Else,
i. Let resolution be ?
importedModule.ResolveExport(in.[[ImportName]], « », « »).
ii. If resolution is null or resolution is "ambiguous", throw a
SyntaxError exception.
iii. Call envRec.CreateImportBinding(in.[[LocalName]],
resolution.[[Module]], resolution.[[BindingName]]).
[...]
15.2.1.16.3 ResolveExport( exportName, resolveSet, exportStarSet )
2. For each Record {[[Module]], [[ExportName]]} r in resolveSet, do:
a. If module and r.[[Module]] are the same Module Record and
SameValue(exportName, r.[[ExportName]]) is true, then
i. Assert: this is a circular import request.
ii. Return null.
3. Append the Record {[[Module]]: module, [[ExportName]]: exportName} to resolveSet.
[...]
5. For each ExportEntry Record e in module.[[IndirectExportEntries]], do
a. If SameValue(exportName, e.[[ExportName]]) is true, then
i. Assert: module imports a specific binding for this export.
ii. Let importedModule be ? HostResolveImportedModule(module,
e.[[ModuleRequest]]).
iii. Let indirectResolution be ?
importedModule.ResolveExport(e.[[ImportName]], resolveSet,
exportStarSet).
iv. If indirectResolution is not null, return indirectResolution.
flags: [module]
---*/
import { a } from './instn-named-iee-cycle-2_.js';
export { c as b } from './instn-named-iee-cycle-2_.js';
export { e as d } from './instn-named-iee-cycle-2_.js';
export { g as f } from './instn-named-iee-cycle-2_.js';
export { i as h } from './instn-named-iee-cycle-2_.js';
export { k as j } from './instn-named-iee-cycle-2_.js';
export { m as l } from './instn-named-iee-cycle-2_.js';
export { o as n } from './instn-named-iee-cycle-2_.js';
export { q as p } from './instn-named-iee-cycle-2_.js';
export { s as r } from './instn-named-iee-cycle-2_.js';
export { u as t } from './instn-named-iee-cycle-2_.js';
export { w as v } from './instn-named-iee-cycle-2_.js';
export { y as x } from './instn-named-iee-cycle-2_.js';
export var z = 23;
assert.sameValue(a, 23);