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d7452b7140
Warn when a non-existent property of an unfinished module.exports
object is being accessed, as that very often indicates the presence
of a hard-to-detect and hard-to-debug problem.
This mechanism is only used if `module.exports` is still a
regular object at the point at which the second, circular `require()`
happens.
The downside is that, temporarily, `module.exports` will have a
prototype other than `Object.prototype`, and that there may
be valid uses of accessing non-existent properties of unfinished
`module.exports` objects.
Performance of circular require calls in general is not
noticeably impacted.
confidence improvement accuracy (*) (**) (***)
module/module-loader-circular.js n=10000 3.96 % ±5.12% ±6.82% ±8.89%
Example:
$ cat a.js
'use strict';
const b = require('./b.js');
exports.fn = () => {};
$ cat b.js
'use strict';
const a = require('./a.js');
a.fn();
$ node a.js
(node:1617) Warning: Accessing non-existent property 'fn' of module exports inside circular dependency
/tmp/b.js:4
a.fn();
^
TypeError: a.fn is not a function
at Object.<anonymous> (/tmp/b.js:4:3)
[...]
PR-URL: https://github.com/nodejs/node/pull/29935
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
35 lines
806 B
JavaScript
35 lines
806 B
JavaScript
'use strict';
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const fs = require('fs');
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const path = require('path');
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const common = require('../common.js');
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const tmpdir = require('../../test/common/tmpdir');
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const benchmarkDirectory =
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path.resolve(tmpdir.path, 'benchmark-module-circular');
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const bench = common.createBenchmark(main, {
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n: [1e4]
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});
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function main({ n }) {
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tmpdir.refresh();
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const aDotJS = path.join(benchmarkDirectory, 'a.js');
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const bDotJS = path.join(benchmarkDirectory, 'b.js');
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fs.mkdirSync(benchmarkDirectory);
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fs.writeFileSync(aDotJS, 'require("./b.js");');
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fs.writeFileSync(bDotJS, 'require("./a.js");');
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bench.start();
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for (let i = 0; i < n; i++) {
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require(aDotJS);
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require(bDotJS);
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delete require.cache[aDotJS];
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delete require.cache[bDotJS];
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}
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bench.end(n);
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tmpdir.refresh();
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}
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