Write path normalization without array allocations #60812
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typescript-bot
added
Author: Team
For Uncommitted Bug
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@typescript-bot perf test this |
| @@ -624,27 +624,103 @@ export function getNormalizedPathComponents(path: string, currentDirectory: stri | |||
| } | |||
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| /** @internal */ | |||
| export function getNormalizedAbsolutePath(fileName: string, currentDirectory: string | undefined): string { | |||
| return getPathFromPathComponents(getNormalizedPathComponents(fileName, currentDirectory)); | |||
| export function getNormalizedAbsolutePath(path: string, currentDirectory: string | undefined): string { | |||
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I wonder if currentDirectory is almost always normalized.
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@andrewbranch Here they are:
tscComparison Report - baseline..pr
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tsserverComparison Report - baseline..pr
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startupComparison Report - baseline..pr
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| const root = path.substring(0, rootLength); | ||
| const normalizedRoot = root && normalizeSlashes(root); | ||
| // `normalized` is only initialized once `path` is determined to be non-normalized | ||
| let normalized = normalizedRoot === root ? undefined : normalizedRoot; |
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You should just use lastIndexOf to see if altDirectorySeparator occurs. That way you can avoid creating a substring for root at all.
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I’m puzzled by the perf results |
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Changing the scenarios to have long paths that are already normalized shows the old |
andrewbranch
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@typescript-bot perf test |
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| const sepIndex = path.indexOf(directorySeparator, index + 1); | ||
| const altSepIndex = path.indexOf(altDirectorySeparator, index + 1); |
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This is quadratic because you have to find at least one of the other kinds of slashes over and over. You should just tight-loop on !isAnyDirectorySeparator.
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or use findIndex(path, isAnyDirectorySeparator, index + 1)
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My only concern with findIndex is that it might not optimize well it passed in both arrays and strings. Maybe I'm superstitious.
| // At beginning of segment | ||
| segmentStart = index; | ||
| let ch = path.charCodeAt(index); | ||
| while (isAnyDirectorySeparator(ch) && index + 1 < path.length) { |
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Took me a bit to see why this works, but it's because index starts immediately after the root, or after the first separator following the prior segment. Figuring out if one of those is a backslash is handled below.
| normalizedUpTo = index + 2; | ||
| } | ||
| } | ||
| else if (normalized === undefined) { |
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I think that in this branch it is technically possible for you to avoid extra substrings by adjusting normalizedUpTo instead of initializing normalized.
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@andrewbranch Here they are:
tscComparison Report - baseline..pr
System info unknown
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Scenarios
tsserverComparison Report - baseline..pr
System info unknown
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Scenarios
startupComparison Report - baseline..pr
System info unknown
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Developer Information: |
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| // the root is `file://Users/` | ||
| assert.strictEqual(ts.getNormalizedAbsolutePath("file://Users/matb/projects/san/../../../../../../typings/@epic/Core.d.ts", ""), "file://Users/typings/@epic/Core.d.ts"); | ||
| // this is real | ||
| assert.strictEqual(ts.getNormalizedAbsolutePath("file:///Users/matb/projects/san/../../../../../../typings/@epic/Core.d.ts", ""), "file:///typings/@epic/Core.d.ts"); |
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idk if we want to preserve specific examples in these, but that might be fine.
Maybe we should have tests on untitled:?
| return path; | ||
| } | ||
| // Some paths only require cleanup of `/./` or leading `./` | ||
| const simplified = path.replace(/\/\.\//g, "/").replace(/^\.\//, ""); |
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If we're already here, I'd also recommend
Suggested change
| const simplified = path.replace(/\/\.\//g, "/").replace(/^\.\//, ""); | |
| let simplified = path.replace(/\/\.\//g, "/"); | |
| if (simplified.startsWith("./") { | |
| simplified = simplified.slice(2); | |
| } |
rbuckton
requested changes
Dec 19, 2024
| let segmentStart = index; | ||
| let normalizedUpTo = index; | ||
| let seenNonDotDotSegment = rootLength !== 0; | ||
| while (index < path.length) { |
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Since path.length doesn't change, it may be more efficient to store it in a local and reuse that rather than look it up each time (both here and elsewhere in the function).
| normalized = path.substring(0, normalizedUpTo); | ||
| } | ||
| } | ||
| else if (segmentLength === 2 && path.charCodeAt(index) === CharacterCodes.dot && path.charCodeAt(index + 1) === CharacterCodes.dot) { |
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Minor nit: If the previous segmentLength was 1, but the segment was not ., this performs an unnecessary recheck of segmentLength === 2.
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| if (normalized === undefined) { | ||
| // Seen superfluous separator | ||
| normalized = path.substring(0, segmentStart - 1); | ||
| } |
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Suggested change
| if (normalized === undefined) { | |
| // Seen superfluous separator | |
| normalized = path.substring(0, segmentStart - 1); | |
| } | |
| // Seen superfluous separator | |
| normalized ??= path.substring(0, segmentStart - 1); |
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| if (segmentEnd === altSepIndex && normalized === undefined) { | ||
| // Seen backslash | ||
| normalized = path.substring(0, segmentStart); | ||
| } |
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Suggested change
| if (segmentEnd === altSepIndex && normalized === undefined) { | |
| // Seen backslash | |
| normalized = path.substring(0, segmentStart); | |
| } | |
| if (segmentEnd === altSepIndex) { | |
| // Seen backslash | |
| normalized ??= path.substring(0, segmentStart); | |
| } |
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| if (normalized === undefined) { | ||
| normalized = path.substring(0, normalizedUpTo); | ||
| } |
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Suggested change
| if (normalized === undefined) { | |
| normalized = path.substring(0, normalizedUpTo); | |
| } | |
| normalized ??= path.substring(0, normalizedUpTo); |
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| let normalized = simpleNormalizePath(path); | ||
| if (normalized !== undefined) { | ||
| return normalized; | ||
| } | ||
| normalized = getNormalizedAbsolutePath(path, ""); | ||
| return normalized && hasTrailingDirectorySeparator(path) ? ensureTrailingDirectorySeparator(normalized) : normalized; |
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The call to hasTrailingDirectorySeparator is redundant as that check is also performed in ensureTrailingDirectorySeparator. This could be simplified to:
Suggested change
| let normalized = simpleNormalizePath(path); | |
| if (normalized !== undefined) { | |
| return normalized; | |
| } | |
| normalized = getNormalizedAbsolutePath(path, ""); | |
| return normalized && hasTrailingDirectorySeparator(path) ? ensureTrailingDirectorySeparator(normalized) : normalized; | |
| return simpleNormalizePath(path) ?? | |
| ensureTrailingDirectorySeparator(getNormalizedAbsolutePath(path, "")); |
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| const sepIndex = path.indexOf(directorySeparator, index + 1); | ||
| const altSepIndex = path.indexOf(altDirectorySeparator, index + 1); |
There was a problem hiding this comment.
or use findIndex(path, isAnyDirectorySeparator, index + 1)
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From instrumenting the compilation of VS Code, I learned two things:
Optimizing I'm going to repeat the instrumentation for a TS Server program update and see if the ratios are similar. |
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During a TS Server update, literally every call is a no-op. |
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Related: #60633
Alternative to #60755
Despite the good benchmarks, I didn’t see any measurable impact in real-world
updateGraphWorkerduration on my M2 Mac Mini. However, since that was a GC hot spot for @dbaeumer and #60755 improved things some, this may do even better for him.bench.js