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fix: hoist import.meta as module-level variable with complete properties (#20658)
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Lines changed: 133 additions & 61 deletions

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‎.changeset/fix-import-meta-standalone-expression.md‎

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@@ -0,0 +1,5 @@
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---
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"webpack": patch
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---
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`import.meta` as standalone expression now returns a complete object with known properties (`url`, `webpack`, `main`, `env`) instead of an empty object `({})`, and hoists it as a module-level variable to ensure `import.meta === import.meta` identity. In `preserve-unknown` mode (ESM output), the hoisted object merges runtime `import.meta` properties via `Object.assign`.

‎AGENTS.md‎

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@@ -53,24 +53,22 @@ Test files live in `test/` with naming conventions:
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- `test/hotCases/` — HMR (Hot Module Replacement) test cases
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- `test/benchmarkCases/` — Performance benchmark cases (each has `index.js` + `webpack.config.mjs` + optional `options.mjs` with `setup()`)
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- `test/*.unittest.js` — Unit tests using Jest directly (e.g., `test/FileSystemInfo.unittest.js` uses `memfs` for filesystem mocking)
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- `test/test262-cases/` — ECMAScript test262 conformance cases (git submodule, init with `git submodule update --init test/test262-cases`; test runner: `test/test262.spectest.js`)
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### 4. Running Tests
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Only run tests when test files are modified or explicitly requested.
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**Choose test command based on modified directory:**
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| Modified directory/file | Command |
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| ----------------------- | ------------------------------------------------------------------------------------- |
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| `test/*.unittest.js` | `yarn test:base -- --testPathPatterns="<filename>"` |
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| `test/cases/` | `yarn test:basic` |
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| `test/configCases/` | `yarn test:basic -- --testPathPatterns="ConfigTestCases"` |
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| `test/statsCases/` | `yarn test:basic -- --testPathPatterns="StatsTestCases"` |
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| `test/watchCases/` | `yarn test:base -- --testPathPatterns="WatchTestCases"` |
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| `test/hotCases/` | `yarn test:base -- --testPathPatterns="HotTestCases"` |
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| `test/benchmarkCases/` | `FILTER="<case-name>" yarn benchmark` |
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| `test/test262-cases/` | `yarn test:test262` (requires `git submodule update --init test/test262-cases` first) |
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| Modified directory/file | Command |
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| ----------------------- | --------------------------------------------------------- |
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| `test/*.unittest.js` | `yarn test:base -- --testPathPatterns="<filename>"` |
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| `test/cases/` | `yarn test:basic` |
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| `test/configCases/` | `yarn test:basic -- --testPathPatterns="ConfigTestCases"` |
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| `test/statsCases/` | `yarn test:basic -- --testPathPatterns="StatsTestCases"` |
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| `test/watchCases/` | `yarn test:base -- --testPathPatterns="WatchTestCases"` |
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| `test/hotCases/` | `yarn test:base -- --testPathPatterns="HotTestCases"` |
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| `test/benchmarkCases/` | `FILTER="<case-name>" yarn benchmark` |
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You can add `--testNamePattern="<case-name>"` to run only specific test cases for faster validation. Multiple patterns can be combined with `|`. For example, if you only modified `test/configCases/css/basic/`:
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@@ -91,7 +89,7 @@ Every user-facing change needs a changeset file:
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Description of the change.
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```
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94-
Use `patch` for bug fixes, `minor` for new features, `major` for breaking changes. Do not prefix the description with `fix:`, `feat:`, etc. — the change type is already indicated by `patch`/`minor`/`major`.
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Use `patch` for bug fixes, `minor` for new features, `major` for breaking changes.
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### 6. Updating Examples (if needed)
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‎lib/dependencies/ImportMetaPlugin.js‎

Lines changed: 38 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,6 @@ const { pathToFileURL } = require("url");
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const { SyncBailHook } = require("tapable");
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const Compilation = require("../Compilation");
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const DefinePlugin = require("../DefinePlugin");
12-
const ModuleDependencyWarning = require("../ModuleDependencyWarning");
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const {
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JAVASCRIPT_MODULE_TYPE_AUTO,
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JAVASCRIPT_MODULE_TYPE_ESM
@@ -23,9 +22,9 @@ const {
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evaluateToString,
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toConstantDependency
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} = require("../javascript/JavascriptParserHelpers");
26-
const memoize = require("../util/memoize");
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const { propertyAccess } = require("../util/property");
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const ConstDependency = require("./ConstDependency");
27+
const ModuleInitFragmentDependency = require("./ModuleInitFragmentDependency");
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/** @typedef {import("estree").MemberExpression} MemberExpression */
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/** @typedef {import("estree").Identifier} Identifier */
@@ -39,10 +38,6 @@ const ConstDependency = require("./ConstDependency");
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/** @typedef {import("../javascript/JavascriptParser").DestructuringAssignmentProperty} DestructuringAssignmentProperty */
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/** @typedef {import("./ConstDependency").RawRuntimeRequirements} RawRuntimeRequirements */
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42-
const getCriticalDependencyWarning = memoize(() =>
43-
require("./CriticalDependencyWarning")
44-
);
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const PLUGIN_NAME = "ImportMetaPlugin";
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/** @type {WeakMap<Compilation, { stringify: string, env: Record<string, string> }>} */
@@ -116,6 +111,11 @@ class ImportMetaPlugin {
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(compilation, { normalModuleFactory }) => {
117112
const hooks = ImportMetaPlugin.getCompilationHooks(compilation);
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114+
compilation.dependencyTemplates.set(
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ModuleInitFragmentDependency,
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new ModuleInitFragmentDependency.Template()
117+
);
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/**
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* @param {NormalModule} module module
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* @returns {string} file url
@@ -181,38 +181,48 @@ class ImportMetaPlugin {
181181
parser.hooks.expression
182182
.for("import.meta")
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.tap(PLUGIN_NAME, (metaProperty) => {
184+
/** @type {RawRuntimeRequirements} */
185+
const runtimeRequirements = [];
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const moduleArgument = parser.state.module.moduleArgument;
187+
184188
const referencedPropertiesInDestructuring =
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parser.destructuringAssignmentPropertiesFor(metaProperty);
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if (!referencedPropertiesInDestructuring) {
187-
const CriticalDependencyWarning =
188-
getCriticalDependencyWarning();
189-
parser.state.module.addWarning(
190-
new ModuleDependencyWarning(
191-
parser.state.module,
192-
new CriticalDependencyWarning(
193-
"'import.meta' cannot be used as a standalone expression. For static analysis, its properties must be accessed directly (e.g., 'import.meta.url') or through destructuring."
194-
),
195-
/** @type {DependencyLocation} */ (metaProperty.loc)
196-
)
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const varName = "__webpack_import_meta__";
192+
const { stringify: envStringify } =
193+
collectImportMetaEnvDefinitions(compilation);
194+
const knownProps =
195+
`{url: ${importMetaUrl()}, ` +
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`webpack: ${importMetaWebpackVersion()}, ` +
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`main: ${RuntimeGlobals.moduleCache}[${RuntimeGlobals.entryModuleId}] === ${moduleArgument}, ` +
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`env: ${envStringify}}`;
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const initCode =
200+
importMeta === "preserve-unknown"
201+
? `var ${varName} = Object.assign(import.meta, ${knownProps});\n`
202+
: `var ${varName} = ${knownProps};\n`;
203+
const initDep = new ModuleInitFragmentDependency(
204+
initCode,
205+
[
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RuntimeGlobals.moduleCache,
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RuntimeGlobals.entryModuleId,
208+
RuntimeGlobals.module
209+
],
210+
varName
197211
);
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initDep.loc = /** @type {DependencyLocation} */ (
213+
metaProperty.loc
214+
);
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parser.state.module.addPresentationalDependency(initDep);
198216
const dep = new ConstDependency(
199-
`${
200-
parser.isAsiPosition(
201-
/** @type {Range} */ (metaProperty.range)[0]
202-
)
203-
? ";"
204-
: ""
205-
}({})`,
206-
/** @type {Range} */ (metaProperty.range)
217+
varName,
218+
/** @type {Range} */ (metaProperty.range),
219+
runtimeRequirements
207220
);
208221
dep.loc = /** @type {DependencyLocation} */ (metaProperty.loc);
209222
parser.state.module.addPresentationalDependency(dep);
210223
return true;
211224
}
212225

213-
/** @type {RawRuntimeRequirements} */
214-
const runtimeRequirements = [];
215-
216226
let str = "";
217227
for (const prop of referencedPropertiesInDestructuring) {
218228
const value = hooks.propertyInDestructuring.call(prop);
@@ -230,7 +240,7 @@ class ImportMetaPlugin {
230240
str += `webpack: ${importMetaWebpackVersion()},`;
231241
break;
232242
case "main":
233-
str += `main: ${RuntimeGlobals.moduleCache}[${RuntimeGlobals.entryModuleId}] === ${RuntimeGlobals.module},`;
243+
str += `main: ${RuntimeGlobals.moduleCache}[${RuntimeGlobals.entryModuleId}] === ${moduleArgument},`;
234244
runtimeRequirements.push(
235245
RuntimeGlobals.moduleCache,
236246
RuntimeGlobals.entryModuleId,

‎test/cases/parsing/asi/warnings.js‎

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@@ -1,7 +1,3 @@
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"use strict";
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3-
module.exports = [
4-
[
5-
/Critical dependency: 'import\.meta' cannot be used as a standalone expression\. For static analysis, its properties must be accessed directly \(e\.g\., 'import\.meta\.url'\) or through destructuring\./
6-
]
7-
];
3+
module.exports = [];

‎test/cases/parsing/import-meta/index.js‎

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@@ -44,10 +44,6 @@ it("should return undefined for unknown property", () => {
4444
expect(() => import.meta.other.other.other).toThrow();
4545
});
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47-
it("should add warning on direct import.meta usage", () => {
48-
expect(Object.keys(import.meta)).toHaveLength(0);
49-
});
50-
5147
it("should support destructuring assignment", async () => {
5248
let version, url2, c;
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({ webpack: version } = { url: url2 } = { c } = import.meta);

‎test/cases/parsing/import-meta/warnings.js‎

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@@ -1,7 +1,3 @@
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"use strict";
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3-
module.exports = [
4-
[
5-
/'import\.meta' cannot be used as a standalone expression\. For static analysis, its properties must be accessed directly \(e\.g\., 'import\.meta\.url'\) or through destructuring\./
6-
]
7-
];
3+
module.exports = [];

‎test/configCases/module/import-meta/index.js‎

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@@ -29,6 +29,13 @@ it("should keep import.meta.UNKNOWN_PROPERTY", () => {
2929
}
3030
});
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32+
it("should preserve runtime properties when import.meta is used as standalone expression", () => {
33+
const meta = (() => import.meta)();
34+
expect(meta.UNKNOWN_PROPERTY).toBe("HELLO");
35+
expect(meta.url).toBeTypeOf("string");
36+
expect(meta.webpack).toBeTypeOf("number");
37+
});
38+
3239
it("should support destructuring assignment", async () => {
3340
let version, url2, c, unknown;
3441
({ webpack: version } =

‎test/configCases/parsing/import-meta-standalone/index.js‎

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1+
import { pathToFileURL } from "url";
2+
import path from "path";
3+
4+
const url = pathToFileURL(
5+
path.resolve("./test/configCases/parsing/import-meta-standalone/index.js")
6+
).toString();
7+
const webpackVersion = parseInt(
8+
// eslint-disable-next-line n/no-missing-require
9+
require("../../../../package.json").version,
10+
10
11+
);
12+
13+
it("should preserve properties when import.meta is assigned to a variable", () => {
14+
const meta = import.meta;
15+
expect(meta.url).toBe(url);
16+
expect(meta.webpack).toBe(webpackVersion);
17+
expect(typeof meta.main).toBe("boolean");
18+
expect(typeof meta.env).toBe("object");
19+
});
20+
21+
it("should preserve properties when import.meta is returned from a function", () => {
22+
function getMeta() {
23+
return import.meta;
24+
}
25+
const meta = getMeta();
26+
expect(meta.url).toBe(url);
27+
expect(meta.webpack).toBe(webpackVersion);
28+
});
29+
30+
it("should preserve properties when import.meta is passed as an argument", () => {
31+
function readUrl(meta) {
32+
return meta.url;
33+
}
34+
expect(readUrl(import.meta)).toBe(url);
35+
});
36+
37+
it("should return the same object for import.meta", () => {
38+
expect(import.meta).toBe(import.meta);
39+
const a = import.meta;
40+
const b = import.meta;
41+
expect(a).toBe(b);
42+
});
43+
44+
it("should preserve runtime properties via Object.assign", () => {
45+
import.meta.CUSTOM_PROP = "custom";
46+
const meta = import.meta;
47+
expect(meta.CUSTOM_PROP).toBe("custom");
48+
expect(meta.url).toBe(url);
49+
});

‎test/configCases/parsing/import-meta-standalone/webpack.config.js‎

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@@ -0,0 +1,13 @@
1+
"use strict";
2+
3+
/** @type {import("../../../../types").Configuration} */
4+
module.exports = {
5+
target: "node",
6+
experiments: {
7+
outputModule: true
8+
},
9+
output: {
10+
module: true,
11+
chunkFormat: "module"
12+
}
13+
};

‎test/test262-cases‎

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