256b5c7e5e
The hybrid xref handler (merge_hybrid) was already implemented. This adds a property-based test to verify it handles random combinations of traditional and stream entries without panicking. Changes: - Added proptest_merge_hybrid_no_panic to proptest_tests module - Tests random entry sets using prop::collection::hash_map - Covers all entry types (InUse, Free, Compressed) - Verification note confirms all acceptance criteria PASS Test results: 9/9 merge_hybrid tests pass Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
69 lines
3.1 KiB
Markdown
69 lines
3.1 KiB
Markdown
# pdftract-5og4: Hybrid Xref Handler Implementation
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## Summary
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Implemented hybrid xref handler that merges traditional table + xref stream with traditional priority. The implementation was already present in the codebase; this verification confirms all acceptance criteria are met.
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## Implementation Status
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### Core Components (Already Implemented)
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1. **`merge_hybrid` function** (xref.rs:197-248)
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- Merges traditional xref table (authoritative) with xref stream (supplementary)
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- Traditional entries always win for overlapping object numbers
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- Stream entries fill gaps not covered by traditional table
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- Sets `is_hybrid: true` on merged result
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- Emits `STRUCT_HYBRID_CONFLICT` diagnostic for Free/InUse conflicts
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2. **`is_hybrid_trailer` function** (xref.rs:260-265)
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- Detects hybrid files by checking for `/XRefStm` key in trailer dict
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3. **Integration in `load_single_xref`** (xref.rs:1964-1984)
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- Checks for hybrid trailer after parsing traditional xref
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- Extracts `/XRefStm` offset
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- Loads supplementary xref stream
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- Merges with traditional taking priority
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## Acceptance Criteria
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| Criterion | Status | Test |
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|-----------|--------|------|
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| Critical test: traditional entries override stream | ✅ PASS | `test_merge_hybrid_traditional_priority` |
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| Stream-only type-2 entries added to merged map | ✅ PASS | `test_merge_hybrid_gap_fill` |
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| Free/InUse conflict emits STRUCT_HYBRID_CONFLICT | ✅ PASS | `test_merge_hybrid_free_inuse_conflict` |
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| Non-hybrid trailer skips merge (pure traditional) | ✅ PASS | `test_is_hybrid_trailer_detection` + `load_single_xref` integration |
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| proptest: random combinations never panic | ✅ PASS | `proptest_merge_hybrid_no_panic` (added) |
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## Changes Made
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### Added Comprehensive Proptest
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Added `proptest_merge_hybrid_no_panic` to the `proptest_tests` module (xref.rs:2416-2447):
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- Tests random combinations of traditional and stream entries
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- Uses prop::collection::hash_map to generate random entry sets
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- Verifies merge_hybrid never panics on any input
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- Covers all entry types (InUse, Free, Compressed)
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## Test Results
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```
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test parser::xref::tests::test_merge_hybrid_stream_only ... ok
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test parser::xref::tests::test_merge_hybrid_free_inuse_conflict ... ok
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test parser::xref::tests::test_merge_hybrid_proptest_simple ... ok
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test parser::xref::tests::test_merge_hybrid_gap_fill ... ok
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test parser::xref::tests::test_merge_hybrid_empty_sections ... ok
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test parser::xref::tests::test_merge_hybrid_traditional_only ... ok
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test parser::xref::tests::test_merge_hybrid_traditional_priority ... ok
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test parser::xref::tests::test_merge_hybrid_trailer_xrefstm_removed ... ok
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test parser::xref::tests::proptest_tests::proptest_merge_hybrid_no_panic ... ok
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test result: ok. 9 passed; 0 failed
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```
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## INV-8 Status
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INV-8 (invariant preservation) is maintained:
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- Traditional entries are never modified or removed
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- Stream entries only added when traditional doesn't have the object number
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- Trailer is taken from traditional with `/XRefStm` removed
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- All diagnostics from both sections preserved
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## References
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- Plan section: Phase 1.3 line 1090 (hybrid files)
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- PDF spec 7.5.8.4 (Hybrid-Reference Files)
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