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module: CJS handle deleted directory relative require #42384

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merged 2 commits into from Oct 31, 2022
Merged

module: CJS handle deleted directory relative require #42384

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af0ee79
module: ensure relative requires work from deleted directories
bmeck Mar 17, 2022
dc3b380
do not use regexes in module loader
aduh95 Oct 29, 2022
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37 changes: 25 additions & 12 deletions lib/internal/modules/cjs/loader.js
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Expand Up @@ -130,9 +130,10 @@ const { validateString } = require('internal/validators');
const pendingDeprecation = getOptionValue('--pending-deprecation');

const {
CHAR_FORWARD_SLASH,
CHAR_BACKWARD_SLASH,
CHAR_COLON
CHAR_COLON,
CHAR_DOT,
CHAR_FORWARD_SLASH,
} = require('internal/constants');

const {
Expand Down Expand Up @@ -538,9 +539,6 @@ function resolveExports(nmPath, request) {
}
}

const trailingSlashRegex = /(?:^|\/)\.?\.$/;
const nixRelativeCheck = /^\.\.?(?:[/]|$)/;
const windowsRelativeCheck = /^\.\.?(?:[/\\]|$)/;
/**
* @param {string} request a relative or absolute file path
* @param {Array<string>} paths file system directories to search as file paths
Expand All @@ -561,14 +559,29 @@ Module._findPath = function(request, paths, isMain) {
return entry;

let exts;
let trailingSlash = request.length > 0 &&
StringPrototypeCharCodeAt(request, request.length - 1) ===
CHAR_FORWARD_SLASH;
if (!trailingSlash) {
trailingSlash = RegExpPrototypeExec(trailingSlashRegex, request) !== null;
}
const trailingSlash = request.length > 0 &&
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I believe storing request.length in a separate variable will result in faster code execution since the next 30~40 lines call request.length

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Historically caching length lookups caused a huge perf hit, since it defeats a JIT optimization - not sure if that’s still true, but i doubt caching the length can beat the JIT.

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I'd be up for landing this as is, and open a new PR to run benchmarks and see if that changes something.

(StringPrototypeCharCodeAt(request, request.length - 1) === CHAR_FORWARD_SLASH || (
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Is there a reason to use charcode instead of:

Suggested change
(StringPrototypeCharCodeAt(request, request.length - 1) === CHAR_FORWARD_SLASH || (
(request[request.length - 1] === '/' || (

?

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I believe charcode comparison is faster

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in recent v8? I’d love to see benchmarks for that!

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Same here, I'd be up for landing this as is, and open a new PR to run benchmarks and see if that changes something.

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Totally agree, perf changes should be done separately with benchmarks - i was thinking the simple string comparison was simpler than the charCode, and thus the better choice absent said benchmarks.

StringPrototypeCharCodeAt(request, request.length - 1) === CHAR_DOT &&
(
request.length === 1 ||
StringPrototypeCharCodeAt(request, request.length - 2) === CHAR_FORWARD_SLASH ||
(StringPrototypeCharCodeAt(request, request.length - 2) === CHAR_DOT && (
request.length === 2 ||
StringPrototypeCharCodeAt(request, request.length - 3) === CHAR_FORWARD_SLASH
))
)
));

const isRelative = RegExpPrototypeExec(isWindows ? windowsRelativeCheck : nixRelativeCheck, request) !== null;
const isRelative = StringPrototypeCharCodeAt(request, 0) === CHAR_DOT &&
(
request.length === 1 ||
StringPrototypeCharCodeAt(request, 1) === CHAR_FORWARD_SLASH ||
(isWindows && StringPrototypeCharCodeAt(request, 1) === CHAR_BACKWARD_SLASH) ||
(StringPrototypeCharCodeAt(request, 1) === CHAR_DOT && ((
request.length === 2 ||
StringPrototypeCharCodeAt(request, 2) === CHAR_FORWARD_SLASH) ||
(isWindows && StringPrototypeCharCodeAt(request, 2) === CHAR_BACKWARD_SLASH)))
);
let insidePath = true;
if (isRelative) {
const normalizedRequest = path.normalize(request);
Expand Down