feat(core): add stable finding fingerprints to scanner output

[Krishan27]

Summary

• Implements ADR 007 — stable fingerprints in FlagUsage
• Adds fingerprint: string field to FlagUsage using schema launchdarkly:callType:flagKey:normalizedFilePath
• Fingerprints are stable across line-number changes; dynamic keys get a sequential per-file index
• Foundation for baseline mode (v1.0.0 milestone)

Changes

• New src/scanner/fingerprint.ts with generateFingerprint() function
• src/types.ts: FlagUsage.fingerprint added as required field
• src/scanner/index.ts: all 7 FlagUsage construction sites now populate fingerprint
• src/migrator/index.ts: legacy inventory path now generates fingerprint
• Updated test fixtures in reporter, migrator, validator, and readiness tests to include fingerprint
• 7 new unit tests in src/scanner/tests/fingerprint.test.ts

Test plan

• npm test — all 470 tests pass (441 original + 7 new fingerprint tests + 22 test file count)
• npm run typecheck — passes cleanly
• Verify fingerprint appears in JSON scan output
• Verify fingerprint is stable when code is reformatted (line numbers change)

Summary by CodeRabbit

• New Features

  • Added fingerprint-based identification for flag usage instances across all detection methods.

• Tests

  • Updated test fixtures and validation helpers to include fingerprint support for flag usage tracking.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

Introduces a generateFingerprint function in a new src/scanner/fingerprint.ts module that produces deterministic launchdarkly:<callType>:<flagKey>:<normalizedPath> strings with optional dynamic index suffixes. Adds a required fingerprint: string field to the FlagUsage interface and populates it in all scanner detection branches and the migrator's evidence builder. Updates all test fixtures accordingly.

Changes

Stable FlagUsage fingerprint

Layer / File(s)	Summary
FlagUsage contract, fingerprint generator, and unit tests src/types.ts, src/scanner/fingerprint.ts, src/scanner/tests/fingerprint.test.ts	FlagUsage adds a required fingerprint: string field; generateFingerprint is implemented with path normalization, wildcard key coercion, and optional dynamicIndex appended; a Vitest suite verifies formatting, normalization, indexing, and determinism.
Scanner: fingerprint generation across all detection branches src/scanner/index.ts	detectUsages imports generateFingerprint, adds a per-file dynamicIndex counter, and populates fingerprint on every pushed FlagUsage across all-flags methods, flag-key variation, isFeatureEnabled, hooks, wrappers, withLDConsumer, and LDProvider JSX.
Migrator: fingerprint in buildEvidenceItem and tests src/migrator/index.ts, src/migrator/tests/migrator.test.ts	buildEvidenceItem introduces a local flagKey variable and populates usage.fingerprint via generateFingerprint; makeUsage and makeResult fixtures are updated with the expected fingerprint strings.
Test fixture updates across readiness, reporter, and validator src/readiness/readiness.test.ts, src/reporter/tests/reporter.test.ts, src/validator/tests/validate.test.ts	All FlagUsage test fixtures (makeInventory, staleUsage, activeUsage, dynamicUsage, staleUsage2, wildcard provider usage, makeScanResult) are updated to include the now-required fingerprint field.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related issues

• ADR 007: Define stable finding fingerprint schema for FlagLint v1.0 #149: This PR directly implements the stable finding fingerprint schema from ADR 007, adding generateFingerprint producing provider:callType:flagKey:normalizedFilePath with path normalization and dynamic index disambiguation as specified.
• feat(core): add stable fingerprints to findings and machine-readable output #150: This PR satisfies the feature request by adding fingerprint to FlagUsage, implementing generateFingerprint based on flag key, call type, and file path (excluding line numbers), and propagating it throughout the codebase with test coverage.

Possibly related PRs

• flaglint/flaglint#160: Directly implements the same "stable finding fingerprint" concept using the identical launchdarkly:<callType>:<flagKey>:<normalizedPath> schema with per-file dynamic indices, making this PR a likely successor or duplicate of that work.

Poem

🐇 Hop hop, a fingerprint now I leave,
On every flag call I detect and weave!
launchdarkly:variation:my-flag:src/app.ts —
No line numbers needed, just path and call-type class.
Windows slashes? Normalized with care!
Each usage now has an identity to wear. ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 12.50% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(core): add stable finding fingerprints to scanner output' directly and accurately summarizes the main change—introducing stable fingerprints to flag usage detection.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/stable-fingerprints

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