Avoid false symlink mappings for physical dependencies by platypii · Pull Request #4813 · microsoft/typescript-go

platypii · 2026-07-31T22:50:43Z

Summary

Fixes declaration emit incorrectly reusing an unrelated JSDoc import when referencing a type from a physically installed dependency.

Related issue: microsoft/TypeScript#63705
Reproduction: https://github.com/platypii/typescript-7-jsdoc-private-alias-repro

Root cause

For a normal, non-symlinked package, ResolvePackageDirectory returns a resolved package directory with an empty OriginalPath.

GetSymlinkCache appended package.json to that empty path before calling ProcessResolution. This produced the relative path package.json, which was then resolved against the project directory. As a result, the symlink cache incorrectly recorded the project root as a symlink to the dependency.

The module specifier generator could consequently treat a project source file as an alternative location for the dependency's type and reuse an unrelated JSDoc module specifier. This produced declarations such as:

schema: import("../src/types.js").SchemaElement[];

even though that module does not export SchemaElement.

Fix

Only add package-directory resolutions to the symlink cache when OriginalPath is non-empty. An empty OriginalPath means there is no symlink mapping to record.

A regression test verifies that declaration emit instead references the type's public external source:

schema: import("external/src/types.js").SchemaElement[];

Reproduction note

The standalone reproduction contains .npmrc with install-links=true only because it models the dependency using a local file: package, which npm would otherwise install as a symlink.

Registry dependencies are normally installed as physical directories under node_modules, so users do not need this npm setting to encounter the bug in a real project.

Tests

go test ./internal/testrunner -run 'TestLocal/jsDeclarationEmitDoesNotReuseUnrelatedJSDocImport' -count=1
go test ./internal/compiler ./internal/modulespecifiers ./internal/symlinks

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The targeted guard matches resolver semantics and the regression test validates the corrected declaration output.

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Pull request overview

Prevents false symlink mappings for physical dependencies, fixing invalid module specifiers during declaration emit.

Changes:

Requires a non-empty OriginalPath before recording package symlinks.
Adds a compiler regression test and expected declaration baseline.

File summaries

File	Description
`internal/compiler/program.go`	Guards symlink-cache insertion for physical packages.
`testdata/tests/cases/compiler/jsDeclarationEmitDoesNotReuseUnrelatedJSDocImport.ts`	Reproduces the declaration-emit regression.
`testdata/baselines/reference/compiler/jsDeclarationEmitDoesNotReuseUnrelatedJSDocImport.js`	Verifies the correct external module specifier.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Balanced

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platypii · 2026-07-31T22:53:30Z

@microsoft-github-policy-service agree company="Hyperparam"

jakebailey · 2026-08-01T05:00:12Z

@typescript-bot test it

typescript-automation · 2026-08-01T05:00:16Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`test top400`	✅ Started	✅ Results
`perf test this faster`	✅ Started	👀 Results

typescript-automation · 2026-08-01T05:26:53Z

@jakebailey
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_119,733	_119,733	_~	_~	_~	_{p=1.000 n=12}
_Types	_99,032	_99,032	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{151,575k (± 0.55%)}	_{151,191k (± 0.50%)}	_~	_149,349k	_152,958k	_{p=0.514 n=12}
_{Memory Allocs}	_{2,262,999 (± 0.00%)}	_{2,263,013 (± 0.00%)}	_~	_2,262,788	_2,263,222	_{p=1.000 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.041s (± 2.48%)}	_{0.041s (± 3.57%)}	_~	_0.037s	_0.045s	_{p=0.630 n=12}
_{Bind Time}	_{0.013s (±13.84%)}	_{0.011s (±10.36%)}	_~	_0.010s	_0.016s	_{p=0.058 n=12}
_{Check Time}	_{0.728s (± 0.50%)}	_{0.733s (± 0.65%)}	_~	_0.724s	_0.746s	_{p=0.052 n=12}
_{Emit Time}	_{0.287s (± 1.43%)}	_{0.284s (± 1.23%)}	_~	_0.272s	_0.289s	_{p=0.354 n=12}
_{Total Time}	_{1.076s (± 0.62%)}	_{1.076s (± 0.42%)}	_~	_1.063s	_1.087s	_{p=0.744 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{871,832 (± 0.10%)}	_{871,444 (± 0.12%)}	_~	_869,245	_874,737	_{p=0.410 n=12}
_Types	_{263,962 (± 0.00%)}	_{263,962 (± 0.00%)}	_~	_263,958	_263,964	_{p=0.946 n=12}
_{Memory Used}	_{806,333k (± 0.06%)}	_{806,622k (± 0.09%)}	_~	_805,096k	_808,875k	_{p=0.713 n=12}
_{Memory Allocs}	_{13,123,773 (± 0.07%)}	_{13,113,231 (± 0.02%)}	_{-10,541 (- 0.08%)}	_13,109,557	_13,118,536	_{p=0.003 n=12}
_{Config Time}	_{0.016s (± 1.75%)}	_{0.016s (± 1.51%)}	_~	_0.016s	_0.017s	_{p=1.000 n=12}
_{Parse Time}	_{0.279s (± 1.91%)}	_{0.281s (± 2.91%)}	_~	_0.260s	_0.295s	_{p=0.541 n=12}
_{Bind Time}	_{0.062s (± 7.00%)}	_{0.064s (±10.72%)}	_~	_0.058s	_0.094s	_{p=0.508 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.699s (± 1.17%)}	_{1.707s (± 1.31%)}	_~	_1.663s	_1.780s	_{p=0.542 n=12}
_{Total Time}	_{2.068s (± 1.29%)}	_{2.081s (± 1.25%)}	_~	_2.034s	_2.172s	_{p=0.355 n=12}
_{mui-docs - native}
_Errors	_{11,277 (± 0.02%)}	_{11,275 (± 0.04%)}	_~	_11,258	_11,282	_{p=0.656 n=12}
_Symbols	_4,387,605	_4,387,605	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,540,346	_1,540,346	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{4,965,332k (± 0.03%)}	_{4,965,286k (± 0.03%)}	_~	_4,961,511k	_4,969,062k	_{p=0.713 n=12}
_{Memory Allocs}	_{45,307,999 (± 0.03%)}	_{45,311,607 (± 0.04%)}	_~	_45,283,888	_45,384,616	_{p=1.000 n=12}
_{Config Time}	_{0.016s (± 1.14%)}	_0.016s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.558s (± 1.47%)}	_{0.546s (± 2.92%)}	_~	_0.502s	_0.576s	_{p=0.354 n=12}
_{Bind Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{16.235s (± 0.48%)}	_{16.322s (± 0.44%)}	_~	_16.132s	_16.449s	_{p=0.131 n=12}
_{Emit Time}	_{0.464s (± 3.03%)}	_{0.457s (± 3.54%)}	_~	_0.440s	_0.518s	_{p=0.896 n=12}
_{Total Time}	_{17.980s (± 0.48%)}	_{18.070s (± 0.43%)}	_~	_17.846s	_18.225s	_{p=0.213 n=12}
_{self-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,394,491	_1,394,491	_~	_~	_~	_{p=1.000 n=12}
_Types	_442,212	_442,212	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,639,173k (± 0.19%)}	_{1,631,002k (± 0.35%)}	_{-8,171k (- 0.50%)}	_1,614,692k	_1,649,259k	_{p=0.008 n=12}
_{Memory Allocs}	_{97,107,646 (± 0.02%)}	_{97,048,008 (± 0.04%)}	_{-59,638 (- 0.06%)}	_96,914,686	_97,167,654	_{p=0.002 n=12}
_{Config Time}	_{0.003s (±11.47%)}	_{0.003s (±16.58%)}	_~	_0.002s	_0.004s	_{p=0.856 n=12}
_{Parse Time}	_{0.197s (± 2.12%)}	_{0.198s (± 2.44%)}	_~	_0.187s	_0.209s	_{p=0.745 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{2.038s (± 0.32%)}	_{2.042s (± 0.32%)}	_~	_2.029s	_2.069s	_{p=0.523 n=12}
_{Emit Time}	_{0.307s (± 3.72%)}	_{0.304s (± 2.28%)}	_~	_0.285s	_0.320s	_{p=0.832 n=12}
_{Total Time}	_{27.360s (± 0.68%)}	_{27.463s (± 0.55%)}	_~	_27.009s	_27.852s	_{p=0.178 n=12}
_{self-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_337,834	_337,834	_~	_~	_~	_{p=1.000 n=12}
_Types	_199,561	_199,561	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{318,357k (± 0.03%)}	_{318,436k (± 0.07%)}	_~	_318,123k	_319,480k	_{p=1.000 n=12}
_{Memory Allocs}	_{4,659,410 (± 0.01%)}	_{4,659,115 (± 0.01%)}	_~	_4,657,799	_4,660,311	_{p=0.478 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.113s (± 4.01%)}	_{0.118s (± 3.57%)}	_~	_0.107s	_0.126s	_{p=0.138 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.219s (± 0.69%)}	_{1.216s (± 0.56%)}	_~	_1.199s	_1.235s	_{p=0.560 n=12}
_{Emit Time}	_{0.167s (± 6.68%)}	_{0.167s (± 6.29%)}	_~	_0.145s	_0.203s	_{p=0.832 n=12}
_{Total Time}	_{1.551s (± 0.93%)}	_{1.553s (± 0.81%)}	_~	_1.525s	_1.589s	_{p=0.921 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_302,246	_302,246	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,594	_181,594	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{274,440k (± 0.02%)}	_{274,451k (± 0.02%)}	_~	_274,209k	_274,624k	_{p=0.504 n=12}
_{Memory Allocs}	_{1,661,250 (± 0.01%)}	_{1,661,364 (± 0.02%)}	_~	_1,660,747	_1,662,430	_{p=0.630 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.099s (± 4.88%)}	_{0.097s (± 3.63%)}	_~	_0.087s	_0.108s	_{p=0.504 n=12}
_{Bind Time}	_{0.038s (±12.84%)}	_{0.035s (± 9.46%)}	_~	_0.029s	_0.045s	_{p=0.337 n=12}
_{Check Time}	_{0.984s (± 0.67%)}	_{0.987s (± 0.52%)}	_~	_0.974s	_1.003s	_{p=0.451 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.135s (± 0.71%)}	_{1.133s (± 0.47%)}	_~	_1.122s	_1.152s	_{p=0.831 n=12}
_{vscode - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_7,631,101	_7,631,101	_~	_~	_~	_{p=1.000 n=12}
_Types	_2,654,831	_2,654,831	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,083,535k (± 0.02%)}	_{5,083,555k (± 0.02%)}	_~	_5,081,390k	_5,085,425k	_{p=0.799 n=12}
_{Memory Allocs}	_{38,640,128 (± 0.04%)}	_{38,639,360 (± 0.03%)}	_~	_38,624,138	_38,680,420	_{p=0.932 n=12}
_{Config Time}	_{0.059s (± 0.55%)}	_{0.059s (± 0.56%)}	_~	_0.058s	_0.059s	_{p=1.000 n=12}
_{Parse Time}	_{1.510s (± 1.64%)}	_{1.491s (± 1.85%)}	_~	_1.381s	_1.543s	_{p=0.318 n=12}
_{Bind Time}	_{0.306s (± 0.43%)}	_{0.325s (±12.82%)}	_~	_0.302s	_0.536s	_{p=0.916 n=12}
_{Check Time}	_{9.734s (± 0.37%)}	_{9.688s (± 0.92%)}	_~	_9.284s	_9.753s	_{p=0.193 n=12}
_{Emit Time}	_{2.792s (± 0.85%)}	_{3.009s (±10.31%)}	_~	_2.724s	_4.426s	_{p=0.098 n=12}
_{Total Time}	_{14.416s (± 0.24%)}	_{14.587s (± 1.67%)}	_~	_14.350s	_15.709s	_{p=0.247 n=12}
_{webpack - native}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_196,816	_196,816	_~	_~	_~	_{p=1.000 n=12}
_Types	₃₄₀	₃₄₀	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{230,680k (± 0.07%)}	_{230,616k (± 0.06%)}	_~	_230,464k	_230,994k	_{p=1.000 n=12}
_{Memory Allocs}	_{975,530 (± 0.43%)}	_{973,514 (± 0.15%)}	_~	_970,621	_977,348	_{p=0.755 n=12}
_{Config Time}	_0.008s	_0.008s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.192s (± 2.52%)}	_{0.192s (± 2.75%)}	_~	_0.176s	_0.202s	_{p=0.660 n=12}
_{Bind Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{0.053s (±13.24%)}	_{0.054s (±16.07%)}	_~	_0.043s	_0.088s	_{p=0.559 n=12}
_{Total Time}	_{0.253s (± 2.63%)}	_{0.255s (± 2.06%)}	_~	_0.242s	_0.273s	_{p=0.504 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,066,055	_1,066,055	_~	_~	_~	_{p=1.000 n=12}
_Types	_392,847	_392,847	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{633,785k (± 0.02%)}	_{633,830k (± 0.01%)}	_~	_633,637k	_634,099k	_{p=0.443 n=12}
_{Memory Allocs}	_{4,919,482 (± 0.03%)}	_{4,918,990 (± 0.04%)}	_~	_4,916,388	_4,924,654	_{p=0.478 n=12}
_{Config Time}	_{0.003s (± 6.23%)}	_0.003s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.154s (± 3.11%)}	_{0.153s (± 3.01%)}	_~	_0.142s	_0.164s	_{p=0.619 n=12}
_{Bind Time}	_{0.043s (±12.71%)}	_{0.053s (±14.73%)}	_~	_0.035s	_0.070s	_{p=0.086 n=12}
_{Check Time}	_{1.276s (± 0.54%)}	_{1.277s (± 0.56%)}	_~	_1.266s	_1.302s	_{p=0.898 n=12}
_{Emit Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.484s (± 0.67%)}	_{1.493s (± 0.50%)}	_~	_1.472s	_1.508s	_{p=0.155 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
mui-docs - native
self-build-src - native
self-compiler - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

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typescript-automation · 2026-08-01T06:12:21Z

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/4813/merge:

Everything looks good!

Avoid false symlink mappings for physical dependencies

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Copilot AI review requested due to automatic review settings July 31, 2026 22:50

Copilot started reviewing on behalf of platypii July 31, 2026 22:51 View session

Copilot AI approved these changes Jul 31, 2026

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Avoid false symlink mappings for physical dependencies - #4813

Avoid false symlink mappings for physical dependencies#4813
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