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module: named exports for CJS via static analysis
PR-URL: #35249 Backport-PR-URL: #35405 Reviewed-By: Mary Marchini <[email protected]> Reviewed-By: Geoffrey Booth <[email protected]> Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Myles Borins <[email protected]> Reviewed-By: Michaël Zasso <[email protected]> Reviewed-By: Zeyu Yang <[email protected]> Reviewed-By: Richard Lau <[email protected]>
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‎LICENSE

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IN THE SOFTWARE.
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"""
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- cjs-module-lexer, located at deps/cjs-module-lexer, is licensed as follows:
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"""
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MIT License
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-----------
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Copyright (C) 2018-2020 Guy Bedford
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Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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"""
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- ICU, located at deps/icu-small, is licensed as follows:
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"""
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COPYRIGHT AND PERMISSION NOTICE (ICU 58 and later)

‎deps/cjs-module-lexer/.gitignore

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node_modules
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*.lock
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test
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.*
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Makefile
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bench
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build.js
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include-wasm
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include
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lib
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src

‎deps/cjs-module-lexer/LICENSE

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MIT License
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-----------
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Copyright (C) 2018-2020 Guy Bedford
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Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

‎deps/cjs-module-lexer/README.md

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# CJS Module Lexer
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[![Build Status][travis-image]][travis-url]
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A [very fast](#benchmarks) JS CommonJS module syntax lexer used to detect the most likely list of named exports of a CommonJS module.
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Outputs the list of named exports (`exports.name = ...`) and possible module reexports (`module.exports = require('...')`), including the common transpiler variations of these cases.
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Forked from https://github.com/guybedford/es-module-lexer.
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_Comprehensively handles the JS language grammar while remaining small and fast. - ~90ms per MB of JS cold and ~15ms per MB of JS warm, [see benchmarks](#benchmarks) for more info._
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### Usage
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```
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npm install cjs-module-lexer
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```
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For use in CommonJS:
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```js
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const parse = require('cjs-module-lexer');
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const { exports, reexports } = parse(`
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// named exports detection
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module.exports.a = 'a';
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(function () {
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exports.b = 'b';
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})();
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Object.defineProperty(exports, 'c', { value: 'c' });
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/* exports.d = 'not detected'; */
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// reexports detection
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if (maybe) module.exports = require('./dep1.js');
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if (another) module.exports = require('./dep2.js');
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// literal exports assignments
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module.exports = { a, b: c, d, 'e': f }
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// __esModule detection
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Object.defineProperty(module.exports, '__esModule', { value: true })
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`);
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// exports === ['a', 'b', 'c', '__esModule']
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// reexports === ['./dep1.js', './dep2.js']
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```
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When using the ESM version, Wasm is supported instead:
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```js
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import { parse, init } from 'cjs-module-lexer';
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// init needs to be called and waited upon
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await init();
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const { exports, reexports } = parse(source);
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```
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The Wasm build is around 1.5x faster and without a cold start.
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### Grammar
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CommonJS exports matches are run against the source token stream.
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The token grammar is:
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```
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IDENTIFIER: As defined by ECMA-262, without support for identifier `\` escapes, filtered to remove strict reserved words:
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"implements", "interface", "let", "package", "private", "protected", "public", "static", "yield", "enum"
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STRING_LITERAL: A `"` or `'` bounded ECMA-262 string literal.
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IDENTIFIER_STRING: ( `"` IDENTIFIER `"` | `'` IDENTIFIER `'` )
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COMMENT_SPACE: Any ECMA-262 whitespace, ECMA-262 block comment or ECMA-262 line comment
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MODULE_EXPORTS: `module` COMMENT_SPACE `.` COMMENT_SPACE `exports`
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EXPORTS_IDENTIFIER: MODULE_EXPORTS_IDENTIFIER | `exports`
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EXPORTS_DOT_ASSIGN: EXPORTS_IDENTIFIER COMMENT_SPACE `.` COMMENT_SPACE IDENTIFIER COMMENT_SPACE `=`
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EXPORTS_LITERAL_COMPUTED_ASSIGN: EXPORTS_IDENTIFIER COMMENT_SPACE `[` COMMENT_SPACE IDENTIFIER_STRING COMMENT_SPACE `]` COMMENT_SPACE `=`
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EXPORTS_LITERAL_PROP: (IDENTIFIER (COMMENT_SPACE `:` COMMENT_SPACE IDENTIFIER)?) | (IDENTIFIER_STRING COMMENT_SPACE `:` COMMENT_SPACE IDENTIFIER)
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EXPORTS_MEMBER: EXPORTS_DOT_ASSIGN | EXPORTS_LITERAL_COMPUTED_ASSIGN
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EXPORTS_DEFINE: `Object` COMMENT_SPACE `.` COMMENT_SPACE `defineProperty COMMENT_SPACE `(` EXPORTS_IDENTIFIER COMMENT_SPACE `,` COMMENT_SPACE IDENTIFIER_STRING
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EXPORTS_LITERAL: MODULE_EXPORTS COMMENT_SPACE `=` COMMENT_SPACE `{` COMMENT_SPACE (EXPORTS_LITERAL_PROP COMMENT_SPACE `,` COMMENT_SPACE)+ `}`
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REQUIRE: `require` COMMENT_SPACE `(` COMMENT_SPACE STRING_LITERAL COMMENT_SPACE `)`
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EXPORTS_ASSIGN: (`var` | `const` | `let`) IDENTIFIER `=` REQUIRE
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MODULE_EXPORTS_ASSIGN: MODULE_EXPORTS COMMENT_SPACE `=` COMMENT_SPACE REQUIRE
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EXPORT_STAR: (`__export` | `__exportStar`) `(` REQUIRE
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EXPORT_STAR_LIB: `Object.keys(` IDENTIFIER$1 `).forEach(function (` IDENTIFIER$2 `) {`
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(
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`if (` IDENTIFIER$2 `===` ( `'default'` | `"default"` ) `||` IDENTIFIER$2 `===` ( '__esModule' | `"__esModule"` ) `) return` `;`? |
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`if (` IDENTIFIER$2 `!==` ( `'default'` | `"default"` ) `)`
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)
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(
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EXPORTS_IDENTIFIER `[` IDENTIFIER$2 `] =` IDENTIFIER$1 `[` IDENTIFIER$2 `]` `;`? |
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`Object.defineProperty(` EXPORTS_IDENTIFIER `, ` IDENTIFIER$2 `, { enumerable: true, get: function () { return ` IDENTIFIER$1 `[` IDENTIFIER$2 `]` `;`? } })` `;`?
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)
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`})`
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```
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* The returned export names are the matched `IDENTIFIER` and `IDENTIFIER_STRING` slots for all `EXPORTS_MEMBER`, `EXPORTS_DEFINE` and `EXPORTS_LITERAL` matches.
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* The reexport specifiers are taken to be the `STRING_LITERAL` slots of all `MODULE_EXPORTS_ASSIGN` as well as all _top-level_ `EXPORT_STAR` `REQUIRE` matches and `EXPORTS_ASSIGN` matches whose `IDENTIFIER` also matches the first `IDENTIFIER` in `EXPORT_STAR_LIB`.
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### Parsing Examples
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#### Named Exports Parsing
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The basic matching rules for named exports are `exports.name`, `exports['name']` or `Object.defineProperty(exports, 'name', ...)`. This matching is done without scope analysis and regardless of the expression position:
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```js
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// DETECTS EXPORTS: a, b, c
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(function (exports) {
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exports.a = 'a';
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exports['b'] = 'b';
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Object.defineProperty(exports, 'c', { value: 'c' });
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})(exports);
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```
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Because there is no scope analysis, the above detection may overclassify:
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```js
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// DETECTS EXPORTS: a, b, c
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(function (exports, Object) {
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exports.a = 'a';
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exports['b'] = 'b';
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if (false)
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Object.defineProperty(exports, 'c', { value: 'c' });
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})(NOT_EXPORTS, NOT_OBJECT);
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```
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It will in turn underclassify in cases where the identifiers are renamed:
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```js
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// DETECTS: NO EXPORTS
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(function (e, defineProperty) {
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e.a = 'a';
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e['b'] = 'b';
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defineProperty(e, 'c', { value: 'c' });
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})(exports, defineProperty);
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```
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#### Exports Object Assignment
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A best-effort is made to detect `module.exports` object assignments, but because this is not a full parser, arbitrary expressions are not handled in the
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object parsing process.
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Simple object definitions are supported:
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```js
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// DETECTS EXPORTS: a, b, c
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module.exports = {
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a,
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b: 'c',
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c: c
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};
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```
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Object properties that are not identifiers or string expressions will bail out of the object detection:
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```js
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// DETECTS EXPORTS: a, b
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module.exports = {
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a,
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b: require('c'),
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c: "not detected since require('c') above bails the object detection"
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}
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```
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`Object.defineProperties` is not currently supported either.
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#### module.exports reexport assignment
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Any `module.exports = require('mod')` assignment is detected as a reexport:
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```js
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// DETECTS REEXPORTS: a, b, c
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module.exports = require('a');
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(module => module.exports = require('b'))(NOT_MODULE);
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if (false) module.exports = require('c');
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```
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As a result, the total list of exports would be inferred as the union of all of these reexported modules, which can lead to possible over-classification.
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#### Transpiler Re-exports
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For named exports, transpiler output works well with the rules described above.
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But for star re-exports, special care is taken to support common patterns of transpiler outputs from Babel and TypeScript as well as bundlers like RollupJS.
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These reexport and star reexport patterns are restricted to only be detected at the top-level as provided by the direct output of these tools.
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For example, `export * from 'external'` is output by Babel as:
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```js
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"use strict";
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exports.__esModule = true;
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var _external = require("external");
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Object.keys(_external).forEach(function (key) {
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if (key === "default" || key === "__esModule") return;
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exports[key] = _external[key];
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});
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```
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Where the `var _external = require("external")` is specifically detected as well as the `Object.keys(_external)` statement, down to the exact
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for of that entire expression including minor variations of the output. The `_external` and `key` identifiers are carefully matched in this
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detection.
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Similarly for TypeScript, `export * from 'external'` is output as:
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```js
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"use strict";
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function __export(m) {
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for (var p in m) if (!exports.hasOwnProperty(p)) exports[p] = m[p];
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}
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Object.defineProperty(exports, "__esModule", { value: true });
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__export(require("external"));
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```
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Where the `__export(require("external"))` statement is explicitly detected as a reexport, including variations `tslib.__export` and `__exportStar`.
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### Environment Support
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Node.js 10+, and [all browsers with Web Assembly support](https://caniuse.com/#feat=wasm).
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### JS Grammar Support
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* Token state parses all line comments, block comments, strings, template strings, blocks, parens and punctuators.
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* Division operator / regex token ambiguity is handled via backtracking checks against punctuator prefixes, including closing brace or paren backtracking.
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* Always correctly parses valid JS source, but may parse invalid JS source without errors.
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### Benchmarks
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Benchmarks can be run with `npm run bench`.
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Current results:
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JS Build:
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```
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Module load time
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> 2ms
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Cold Run, All Samples
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test/samples/*.js (3635 KiB)
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> 333ms
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Warm Runs (average of 25 runs)
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test/samples/angular.js (1410 KiB)
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> 16.48ms
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test/samples/angular.min.js (303 KiB)
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> 5.36ms
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test/samples/d3.js (553 KiB)
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> 8.32ms
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test/samples/d3.min.js (250 KiB)
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> 4.28ms
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test/samples/magic-string.js (34 KiB)
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> 1ms
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test/samples/magic-string.min.js (20 KiB)
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> 0.36ms
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test/samples/rollup.js (698 KiB)
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> 10.48ms
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test/samples/rollup.min.js (367 KiB)
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> 6.64ms
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Warm Runs, All Samples (average of 25 runs)
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test/samples/*.js (3635 KiB)
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> 49.28ms
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```
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Wasm Build:
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```
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Module load time
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> 11ms
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Cold Run, All Samples
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test/samples/*.js (3635 KiB)
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> 48ms
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Warm Runs (average of 25 runs)
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test/samples/angular.js (1410 KiB)
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> 12.32ms
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test/samples/angular.min.js (303 KiB)
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> 3.76ms
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test/samples/d3.js (553 KiB)
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> 6.08ms
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test/samples/d3.min.js (250 KiB)
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> 3ms
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test/samples/magic-string.js (34 KiB)
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> 0.24ms
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test/samples/magic-string.min.js (20 KiB)
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> 0ms
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test/samples/rollup.js (698 KiB)
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> 7.2ms
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test/samples/rollup.min.js (367 KiB)
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> 4.2ms
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Warm Runs, All Samples (average of 25 runs)
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test/samples/*.js (3635 KiB)
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> 33.6ms
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```
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### Wasm Build Steps
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To build download the WASI SDK from https://github.com/CraneStation/wasi-sdk/releases.
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The Makefile assumes the existence of "wasi-sdk-10.0", "binaryen" and "wabt" (both optional) as sibling folders to this project.
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The build through the Makefile is then run via `make lib/lexer.wasm`, which can also be triggered via `npm run build-wasm` to create `dist/lexer.js`.
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On Windows it may be preferable to use the Linux subsystem.
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After the Web Assembly build, the CJS build can be triggered via `npm run build`.
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Optimization passes are run with [Binaryen](https://github.com/WebAssembly/binaryen) prior to publish to reduce the Web Assembly footprint.
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### License
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MIT
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[travis-url]: https://travis-ci.org/guybedford/es-module-lexer
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[travis-image]: https://travis-ci.org/guybedford/es-module-lexer.svg?branch=master

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