test: capture resolved statements

[huytdps13400]

Summary

• add a CAPTURE_FOLLOWING() no-op marker and captureStatements() helper for inspecting ResolvedStatement output
• keep pending captures scoped to the current block so nested statements and separately resolved helper functions cannot consume them
• preserve the existing captureSnippets(): Snippet[] contract instead of widening it to a mixed union
• reject markers that are not followed by a statement

Closes #2715.

Verification

• focused capture suite: 11/11 passed
• full source suite with bounded workers: 275 files, 2,872 passed, 2 skipped
• built package suite with attest enabled: 243 files, 2,443 passed, 2 skipped
• full monorepo typecheck: 0 errors
• full Oxlint/Prettier/Oxfmt style gate: passed
• circular dependency check: passed
• git diff --check: passed

The default highly parallel source run twice hit the existing 5-second timeout in typegpu-docs probability example; that test passed alone in 662 ms, and the complete suite passed with --maxWorkers=4.

[Copilot]

Pull request overview

Adds a new testing-only capture mechanism to inspect resolved statement output from the WGSL generator, complementing the existing snippet capture utilities.

Changes:

• Introduces CAPTURE_FOLLOWING() marker and captureStatements() helper to collect ResolvedStatement results during resolution.
• Scopes “pending capture” state to the current block to avoid nested blocks or other resolves consuming it.
• Expands internal test coverage to validate marker no-op behavior, capturing semantics, and error cases.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/typegpu/tests/internal/capturedSnippets.test.ts	Adds a focused test suite for CAPTURE_FOLLOWING + captureStatements behavior and error handling.
packages/typegpu-testing-utility/src/index.ts	Re-exports CAPTURE_FOLLOWING and captureStatements from the testing utility package entrypoint.
packages/typegpu-testing-utility/src/capture.ts	Implements statement capture plumbing in a custom WgslGenerator and adds the new marker/helper API.

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[pullfrog]

Important

captureStatements returns .code that can still contain unresolved #VAR_n# placeholder tokens, so the captured text diverges from what actually lands in the shader for non-scalar let/const declarations and loops. See the inline comment on capture.ts.

Reviewed changes — one commit (dc530ca, "test: capture resolved statements") that adds a statement-capture facility to typegpu-testing-utility for inspecting ResolvedStatement output:

• CAPTURE_FOLLOWING(): a dualImpl no-op whose call CapturingGenerator._expression intercepts to set a per-block capture flag (packages/typegpu-testing-utility/src/capture.ts).
• _statement/_block overrides: consume the flag on the next statement, scope capture state per block with a stack so nested statements and separately resolved helpers can't consume another block's flag, and throw when a marker isn't followed by a statement.
• captureStatements() helper, index.ts re-exports, and five new tests in packages/typegpu/tests/internal/capturedSnippets.test.ts.

Verified the focused suite passes locally (11/11) and probed edge cases (loop bodies, comptime-pruned statements, inner-block markers) with scratch tests that were deleted afterward.

ℹ️ Nitpicks

• A marker followed by a statement that comptime-folds to nothing (e.g. CAPTURE_FOLLOWING(); if (false) { ... }) silently captures an empty { code: '' } statement and consumes the marker. Harmless, but a test author may be surprised; a one-line doc note on captureStatements (or skipping empty-code captures) would cover it.

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[pullfrog]

✅ No new issues found.

Reviewed changes — one new commit (acd21101, "fix: normalize captured statements") that resolves the prior review's finding that captured statement .code leaked unresolved #VAR_n# placeholders for non-scalar declarations and loops:

• Factored the deferred-var substitution out of WgslGenerator.functionDefinition into a shared protected _replaceVariablePlaceholders(code) (packages/typegpu/src/tgsl/wgslGenerator.ts), preserving exact behavior in the existing call site.
• Added a CapturingGenerator.functionDefinition override that applies the finalized function-scope placeholderForVariable/modifiedVariables mapping to statements captured during that function's generation, so captured text matches the emitted shader.
• CAPTURE_FOLLOWING() markers now resolve to an empty statement instead of falling through, and consecutive markers in the same block throw 'CAPTURE_FOLLOWING must be followed by a statement'.
• Added tests for consecutive-marker rejection and for deferred-placeholder resolution across a non-scalar const plus a for loop. The latter is genuine regression coverage — it fails when the new override is removed (verified by mutation) — and cross-checks each captured statement against the emitted shader.
• Documented on captureStatements that a comptime-pruned following statement captures an empty { code: '' } (covers the prior nitpick).

The prior review's placeholder-divergence thread was resolved. The wgslGenerator.ts change is behavior-preserving; the internal suite (431 tests) and typechecks for both packages pass, and the nested-helper capture path (marker inside a separately-resolved tgpuFn) was verified at runtime.

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