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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.
47 lines
1.8 KiB
JavaScript
47 lines
1.8 KiB
JavaScript
// Copyright (C) 2016 the V8 project authors. All rights reserved.
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// This code is governed by the BSD license found in the LICENSE file.
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/*---
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description: Imported binding reflects state of exported `const` binding
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esid: sec-moduledeclarationinstantiation
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info: |
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[...]
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12. For each ImportEntry Record in in module.[[ImportEntries]], do
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a. Let importedModule be ? HostResolveImportedModule(module,
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in.[[ModuleRequest]]).
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b. If in.[[ImportName]] is "*", then
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[...]
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c. Else,
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i. Let resolution be ?
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importedModule.ResolveExport(in.[[ImportName]], « », « »).
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ii. If resolution is null or resolution is "ambiguous", throw a
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SyntaxError exception.
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iii. Call envRec.CreateImportBinding(in.[[LocalName]],
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resolution.[[Module]], resolution.[[BindingName]]).
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[...]
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16. Let lexDeclarations be the LexicallyScopedDeclarations of code.
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17. For each element d in lexDeclarations do
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a. For each element dn of the BoundNames of d do
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i, If IsConstantDeclaration of d is true, then
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1. Perform ! envRec.CreateImmutableBinding(dn, true).
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ii. Else,
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1. Perform ! envRec.CreateMutableBinding(dn, false).
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iii. If d is a GeneratorDeclaration production or a
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FunctionDeclaration production, then
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[...]
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8.1.1.5.5 CreateImportBinding
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[...]
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5. Create an immutable indirect binding in envRec for N that references M
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and N2 as its target binding and record that the binding is initialized.
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6. Return NormalCompletion(empty).
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flags: [module]
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---*/
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assert.throws(ReferenceError, function() {
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typeof y;
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}, 'binding is created but not initialized');
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import { x as y } from './instn-named-bndng-let.js';
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export let x = 23;
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