Phase 4: investigate VS Code JS/TS parse syntax gaps

[jununfly]

This was generated by AI during triage.

What to build

Investigate the real supported JS/TS syntax gaps surfaced by the VS Code large-target parse-error taxonomy.

Issue #86 classified the 46 parse errors from the #81 VS Code profile. Most are intentional malformed fixtures or prompt/generated non-app source, but 16 paths look like normal supported JavaScript/TypeScript source or tests and should be investigated as parser coverage gaps rather than waived.

Evidence

Source artifact:

• docs/benchmarks/2026-06-13-rust-indexing-core-phase-4-vscode-profile.raw.json

Representative real syntax-gap paths:

• build/next/index.ts
• extensions/copilot/src/extension/byok/vscode-node/test/geminiNativeProvider.spec.ts
• extensions/copilot/src/extension/chatSessions/claude/vscode-node/test/claudeSlashCommandService.spec.ts
• extensions/copilot/src/extension/chatSessions/copilotcli/node/test/copilotcliSession.spec.ts
• extensions/copilot/src/extension/chatSessions/copilotcli/vscode-node/test/chatSessionMetadataStoreImpl.spec.ts
• extensions/copilot/src/extension/chatSessions/copilotcli/vscode-node/test/lockFile.spec.ts
• extensions/copilot/src/extension/typescriptContext/serverPlugin/src/common/typescripts.ts
• extensions/copilot/src/platform/telemetry/common/telemetry.ts
• src/vs/code/electron-browser/workbench/workbench.ts
• src/vs/platform/agentHost/node/claude/claudeSubagentSignals.ts
• src/vs/platform/browserView/electron-browser/preload-browserView.ts
• src/vs/platform/tunnel/test/node/tunnelProxy.test.ts
• src/vs/sessions/electron-browser/sessions.ts
• src/vs/workbench/contrib/chat/test/common/promptSyntax/hookSchema.test.ts
• src/vs/workbench/contrib/issue/browser/issueFormService.ts
• src/vs/workbench/contrib/terminal/test/browser/terminalProfileService.integrationTest.ts

Acceptance criteria

• Each real syntax-gap path is reduced to a minimal parser fixture or explained as a false positive in the taxonomy.
• The root syntax feature is identified for each failing family.
• Fixes include targeted parser/extractor coverage where appropriate.
• Re-running the VS Code parse-error taxonomy moves fixed paths out of the real syntax-gap bucket.
• Any remaining unfixed paths are explicitly listed as rollout blockers or accepted limitations.

Agent notes

Do not require VS Code to reach zero parse errors. This issue is only for the real supported JS/TS syntax-gap subset; malformed fixtures and prompt/generated non-app source should remain documented separately.

[jununfly]

Status update from Phase 4 branch codex/issue-87-reference-resolution-profile, commit 5400ec4.

#86 classified all 46 VS Code parse errors and is now closed. The taxonomy is recorded in:

• docs/benchmarks/2026-06-13-rust-indexing-core-phase-4-vscode-parse-error-taxonomy.md

This issue remains open and is the targeted follow-up for the 16 real supported JS/TS syntax-gap paths. Phase 4 does not require zero parse errors, but the real syntax-gap subset remains a default-rollout blocker in:

• docs/benchmarks/2026-06-13-rust-indexing-core-phase-4-results-and-decision.md

[jununfly]

Implemented in branch codex/issue-88-vscode-syntax-gaps, commit c44951b.

What changed:

• Rust core now normalizes parser input for modern TypeScript syntax that the current tree-sitter-typescript grammar rejects while keeping the original source for extraction.
• Fixed the two real syntax-gap families from the VS Code taxonomy:
  • type-only import queries such as import('module').Type and typeof import('module')
  • contextual keyword identifiers such as abstract: property names and unique. member receivers

Evidence added:

• docs/benchmarks/2026-06-14-rust-indexing-core-phase-4-vscode-syntax-gap-resolution.md
• docs/benchmarks/2026-06-14-rust-indexing-core-phase-4-vscode-syntax-gap-rerun.raw.json
• docs/benchmarks/2026-06-14-rust-indexing-core-phase-4-vscode-syntax-gap-full-rerun.raw.json

Results:

• Targeted 16-path Phase 4: investigate VS Code JS/TS parse syntax gaps #88 slice: filesErrored=0.
• Full VS Code JS/TS sparse-checkout Rust parse rerun: parse errors reduced from 46 to 29.
• All 16 real supported JS/TS syntax-gap paths moved out of the parse-error set.
• Remaining 29 parse errors are the malformed fixture, prompt/generated, or compiler-scale colorization fixture paths already classified by Phase 4: classify VS Code large-target parse errors #86.

Validation:

• cargo test --package zcodegraph-core
• npm run build
• npx vitest run tests/rust-phase4-vscode-syntax-gap-resolution-doc.test.ts tests/rust-phase4-vscode-parse-taxonomy-doc.test.ts tests/rust-phase4-results-decision-doc.test.ts tests/rust-phase4-release-notes-doc-links.test.ts
• Full VS Code sparse Rust parse rerun
• git diff --check

Decision impact: #88 is no longer a default-rollout blocker. Phase 4 still remains on the continue opt-in + targeted blockers path because the #87 reference-resolution database-access bottleneck remains unresolved.