Detect conflicting output paths across build steps

[bcomnes]

Summary

Closes #288.

Enforce one producer per destination-relative output path across pages, generated pages, templates, static assets, copied directories, esbuild bundles, service workers, and generated metadata. Conflicts fail with DOM_STACK_ERROR_OUTPUT_CONFLICT and identify the output path and both producers instead of silently choosing whichever write finishes last.

Implementation

• Add a shared output registry with separator normalization, destination-filesystem case handling, file-versus-directory checks, and duplicate-record handling distinct from duplicate writes.
• Claim esbuild outputs before buffered emission and isolate copy sources before publication; attribute identifiable native esbuild entry collisions to both sources.
• Reserve page outputs before concurrent template rendering, including dynamic arrays and async iterators.
• Keep ownership for untouched watch producers, compute replacement ownership once in the page worker, and revalidate against current ownership before serialized promotion.
• Consolidate copy-watch startup into one inventory, buffer startup changes, and preserve independent mappings from overlapping copy roots.
• Release obsolete ownership after successful replacements and removals, and replace the complete ownership map on full watch builds.
• Preserve manifest-hook read-after-write behavior and public copy-report destination mappings.

Scope and tradeoffs

Ordinary one-shot builds do not stage or roll back the whole site: earlier successful writes may remain after a later failure, but a conflicting second producer cannot overwrite the first. Incremental page phases, full watch builds, and copy isolation retain staging where needed for checked publication. Stages use the destination filesystem.

This is a cross-cutting build/watch change rather than a small validation check. It adds ownership bookkeeping, buffered output, temporary disk usage, and a separate promotion lock to coordinate esbuild with page workers. Performance has not been benchmarked.

Publication is not atomic against filesystem I/O failures. Arbitrary filesystem writes by user code or plugins bypass the registry, separate instances are not coordinated when publishing to the same destination, and unattributable esbuild plugin/shared-chunk collisions retain native diagnostics. Initial copy/esbuild failures abort watch startup and require restarting; conflicts in a successfully started session can recover after correcting the source.

Validation

• Full Node suite: 237 passed, 0 failed, 2 skipped. Skips require a source filesystem capable of representing case aliases.
• Repository-wide ESLint: passed.
• TypeScript: passed.
• Installed dependency check: passed during the simplification validation pass.
• git diff --check: passed.
• Playwright: 11 passed, 2 failed at the known All recipes and All migrations documentation-navigation timeouts. Both failures were previously reproduced on clean HEAD; unrelated browser behavior was left unchanged.

Regression coverage includes cross-producer collisions, dynamic template outputs, filtered watch conflicts, esbuild/page promotion races, startup copy changes, rename/removal recovery, overlapping copy roots, hook read-back, copy-report mappers, and recovery after promotion I/O failure.

Review focus

• Output ownership replacement and cleanup across filtered and full watch builds.
• Copy inventory/startup event draining and overlapping source roots.
• The retained staging boundaries and explicit non-atomic publication guarantee.
• Compatibility of controlled esbuild emission with custom settings and plugins.

[coveralls]

Coverage Report for CI Build 34791088100

Coverage increased (+0.5%) to 94.769%

Details

• Coverage increased (+0.5%) from the base build.
• Patch coverage: 14 uncovered changes across 5 files (991 of 1005 lines covered, 98.61%).
• 1 coverage regression across 1 file.

Uncovered Changes

File	Changed	Covered	%
index.js	268	260	97.01%
lib/build-pages/index.js	150	147	98.0%
lib/build-esbuild/index.js	113	112	99.12%
lib/build-esbuild/output-conflicts.js	70	69	98.57%
lib/output-registry.js	174	173	99.43%
Total (13 files)	1005	991	98.61%

Coverage Regressions

1 previously-covered line in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
index.js	1	95.51%

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Coverage Stats

Relevant Lines:	9797
Covered Lines:	9438
Line Coverage:	96.34%
Relevant Branches:	2667
Covered Branches:	2374
Branch Coverage:	89.01%
Branches in Coverage %:	Yes
Coverage Strength:	406.73 hits per line

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💛 - Coveralls