fix(debug): normalize Windows PATH env keys

[xclear-cast]

Summary

• normalize Windows search-path environment keys to the debugger's preferred Path casing before handing env vars to debugpy
• merge alternate PATH values into Path by path segment so duplicate keys and duplicate path entries are avoided
• add a VS Code-hosted unit test covering a launch env that supplies PATH while Windows uses Path

Fixes #261.

Validation

pm ci --ignore-scripts to install JS dependencies after plain
pm ci hit a local native build-tools blocker in @vscode/windows-process-tree (MSB8040, missing Spectre-mitigated VC libraries)

pm run compile-tests

pm run lint

pm run format-check

pm run compile

• TEST_GREP='duplicate Windows search path' node ./out/test/runTest.js
• git diff --check

The focused VS Code-hosted unit test passed: 1 passing.

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[rchiodo]

Copilot generated:
-95

Test fails on non-Windows CI (Skeptic, structurally confirmed). sinon.stub(platform, 'getOSType').returns(platform.OSType.Windows) makes getSearchPathEnvVarNames() return ['Path', 'PATH'], but path.delimiter remains : on Linux/macOS — it's a Node.js runtime constant, not controlled by the stub. The production code in normalizeSearchPathEnvVar uses path.delimiter to split/join segments, so on Linux env.Path will contain : delimiters. The assertions then split by hardcoded ';', which won't match.

Fix options:

1. Use path.delimiter in assertions instead of hardcoded ';'
2. Also stub/mock path.delimiter to ';'
3. Skip the test on non-Windows: if (process.platform !== 'win32') return

[verified]

[rchiodo]

Copilot generated:
-91

Partial assertions violate test precision (Rules). .to.contain(...) would still pass if env.Path contained extra duplicates, wrong delimiters, or unrelated segments — exactly the regression class this test should catch:

expect(env.Path).to.contain('C:\\Project\\.venv\\Scripts');
expect(env.Path).to.contain('C:\\Tools');

Fix: Capture the exact runtime value of env.Path (via debugger or a passing run) and assert with .to.equal('<exact-full-string>'). This ensures the full merged, deduplicated, correctly-delimited value is validated.

[verified]

[rchiodo]

Copilot generated:
-102

Missing edge case coverage (Skeptic + Architect). The test only covers the internalConsole code path (which triggers mergeVariables(process.env, env)). Consider adding:

1. A non-internalConsole mode test to verify the earlier normalization calls work independently.
2. A test confirming Linux/macOS (PATH-only, single key) is unaffected by normalization.
3. [unverified] On Windows Node.js, process.env is case-insensitive, so process.env.Path = 'X'; process.env.PATH = 'Y' may alias to the same entry. The test's process.env setup may not create the two-key scenario it appears to — the args.env plain-object path still exercises the core logic, but the process.env interaction is less realistic than intended.

[verified]

[rchiodo]

Copilot generated:
,12

Readonly parameters (Rules). Both new helpers accept names: ('Path' | 'PATH')[] but never mutate it. vars in getSearchPathEnvVar is only read (.map, .find). Per the repo's immutability-by-default convention:

function getSearchPathEnvVar(vars: Readonly<EnvironmentVariables>, names: readonly ('Path' | 'PATH')[]): ...
function normalizeSearchPathEnvVar(env: EnvironmentVariables, names: readonly ('Path' | 'PATH')[]) { ...

(env is intentionally mutable since the function modifies it.)

[verified]

[rchiodo]

Copilot generated:
-35

Case-sensitive path segment deduplication on a case-insensitive filesystem (Skeptic, structurally confirmed; Architect concurs). The Set.has() check uses === semantics. On Windows, C:\Windows\System32 and c:\windows\system32 refer to the same directory but would survive deduplication.

The Advocate correctly notes this matches pre-existing behavior in appendPath/appendPaths. However, the PR description claims "duplicate path entries are avoided" — case-insensitive duplicates are not. Consider normalizing with .toLowerCase() for the lookup Set while preserving original casing in the output, or document this as a known limitation.

[verified]

[rchiodo]

Copilot generated:
-100

Root cause assessment — symptom treatment, not root fix (Architect + Skeptic). Five normalizeSearchPathEnvVar calls are needed because mergeVariables in environment.ts only excludes getSearchPathEnvVarNames()[0] (i.e., Path), letting PATH through on every merge. The normalization is idempotent and correct (Advocate), but fragile — any future merge/append without a following normalize silently regresses the bug (Architect).

Recommended follow-up: fix environment.ts line ~55 to settingsNotToMerge = ['PYTHONPATH', ...getSearchPathEnvVarNames()]. This one-line change would eliminate most normalize calls and protect all consumers of mergeVariables, not just the debugger. If not addressed in this PR, add a TODO comment explaining why each normalize call exists.

[verified]