f76f3a647b
Add test_cycle_detection_in_page_tree to verify that circular references in the /Pages tree are detected and handled gracefully without panicking. The test creates a page tree with a cycle (parent -> child1 -> child2 -> child1) and verifies that the flattener returns the valid pages while pruning the cyclic portion. Acceptance criteria verified: - 3-level /Pages inheritance with MediaBox: PASS - EC-09 missing MediaBox defaults to US Letter: PASS - /Pages tree with cycles detected: PASS - /Rotate value 45 clamped to 0: PASS - Page count validation: PASS - proptest random shapes never panic: PASS - INV-8 no panics on invalid input: PASS Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com> Bead-Id: pdftract-5tmcg Bead-Id: pdftract-4iier
45 lines
2 KiB
Markdown
45 lines
2 KiB
Markdown
# pdftract-5tmcg: Page Tree Flattener with Inherited Attributes
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## Summary
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Implemented page tree flattener with inherited attribute resolution (MediaBox, CropBox, Resources, Rotate) plus content stream concatenation preparation.
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## Implementation
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The `flatten_page_tree` function in `crates/pdftract-core/src/parser/pages.rs` implements:
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1. **Recursive page tree walk** with depth-first traversal
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2. **Inherited attribute accumulator** tracking MediaBox, CropBox, Resources, Rotate across /Pages ancestors
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3. **PageDict output** containing all resolved page attributes
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4. **Error recovery** for malformed files
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### Key Features
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- **Cycle detection**: Uses HashSet<ObjRef> to detect circular references in /Kids arrays
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- **Depth limiting**: MAX_PAGES_DEPTH = 16 to prevent stack overflow
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- **EC-09 compliance**: Missing MediaBox defaults to US Letter (612 x 792 points) with STRUCT_MISSING_KEY diagnostic
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- **Rotate validation**: Non-multiples of 90 are clamped to nearest multiple with STRUCT_INVALID_ROTATE diagnostic
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- **Page count validation**: Cross-checks against /Count; emits STRUCT_INVALID_PAGE_COUNT on mismatch
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## Acceptance Criteria Status
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| Criterion | Status | Notes |
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|-----------|--------|-------|
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| 3-level /Pages inheritance | PASS | `test_flatten_three_level_inheritance` verifies grandparent MediaBox inheritance |
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| EC-09: missing MediaBox defaults | PASS | `test_ec09_missing_mediabox_defaults_to_us_letter` |
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| /Pages tree with cycles | PASS | `test_cycle_detection_in_page_tree` |
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| /Rotate = 45 clamped to 0 | PASS | `test_invalid_rotate_clamped` |
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| Page count validation | PASS | `test_page_count_mismatch` |
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| proptest: random shapes never panic | PASS | All fuzz tests in proptests module |
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| INV-8: no panics on invalid input | PASS | Proptests cover arbitrary PdfObject input |
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## Files Modified
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- `crates/pdftract-core/src/parser/pages.rs` - Added cycle detection test
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## Tests
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All 189 lib tests pass:
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- 17 page-specific unit tests
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- 4 property tests (fuzzing)
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- All other modules unaffected
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