feat: Implement PDF heading hierarchy inference for category_depth by ylcnymn · Pull Request #4369 · Unstructured-IO/unstructured

ylcnymn · 2026-06-09T20:56:57Z

Summary

Implements PDF heading hierarchy inference to populate category_depth metadata field for Title elements based on relative font sizes, addressing issue #4204.

Changes

Helper Functions Added:
- _extract_font_sizes_from_text_obj(): Extracts font sizes from LTChar objects within PDF text
- _get_representative_font_size(): Calculates median font size (robust to outliers)
- _infer_category_depth_from_font_size(): Infers heading hierarchy levels (H1-H6)
Integration:
- Page-level font size collection for relative sizing context
- Per-element category_depth calculation and assignment
- Populates ElementMetadata.category_depth for PDF Title elements

Implementation Details

Uses median font size to avoid outliers (superscripts, drop caps)
Identifies body text as most frequent font size and filters it out
Maps remaining font sizes to heading levels (1-6) in descending order
Only applies to Title elements (returns None for other types)

Testing

Syntax validation: ✅ PASSED
Package build: ✅ PASSED
Manual code review: ✅ PASSED

Resolves

Closes #4204

Summary by cubic

Infers PDF heading hierarchy from relative font sizes and sets category_depth for Title elements. Adds recursive page-level font-size collection (incl. nested containers), closest-match tolerance, per-object caching, and 20 tests; fixes test helper to set LTChar bbox. Closes #4204.

New Features
- Uses per-page font-size frequencies from recursive collection (includes nested containers) to ignore body text; maps median Title size to levels 1–6.
- Caches per-object font sizes and applies closest-match logic with 1pt tolerance when medians don’t match page font sizes.

^{Written for commit 273cb3c. Summary will update on new commits.}

- Add _extract_font_sizes_from_text_obj() to extract font sizes from LTChar objects - Add _get_representative_font_size() to calculate median font size (robust to outliers) - Add _infer_category_depth_from_font_size() to infer heading levels (H1-H6) - Integrate category_depth calculation into PDF partition flow at page and element level - Populate ElementMetadata.category_depth for Title elements based on relative font sizes - Use median font size and frequency-based body text filtering for accurate hierarchy Resolves Unstructured-IO#4204 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cubic-dev-ai

3 issues found across 1 file

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="unstructured/partition/pdf.py">

<violation number="1" location="unstructured/partition/pdf.py:576">
P2: Custom agent: **Enforce Pragmatic Test Coverage**

Core PDF parsing behavior was changed to infer and persist `category_depth`, but no accompanying tests are included for the new helper functions or their integration path.</violation>
</file>

_{Shadow auto-approve: would not auto-approve because issues were found.

Fix all with cubic | Re-trigger cubic}

cubic-dev-ai · 2026-06-09T21:00:27Z

                        last_modified=metadata_last_modified,
                        links=links,
                        languages=languages,
+                        category_depth=category_depth,


P2: Custom agent: Enforce Pragmatic Test Coverage

Core PDF parsing behavior was changed to infer and persist category_depth, but no accompanying tests are included for the new helper functions or their integration path.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At unstructured/partition/pdf.py, line 576: <comment>Core PDF parsing behavior was changed to infer and persist `category_depth`, but no accompanying tests are included for the new helper functions or their integration path.</comment> <file context> @@ -548,13 +556,24 @@ def _process_pdfminer_pages( last_modified=metadata_last_modified, links=links, languages=languages, + category_depth=category_depth, ) element.metadata.detection_origin = "pdfminer" </file context>

@cubic-dev-ai

- Fix P1: Use closest-match logic for font size hierarchy inference Resolves median floating-point edge case where calculated median may not exist in discrete page_font_sizes keys. Add 1pt tolerance. - Fix P2: Eliminate duplicated font extraction via obj_font_cache Cache font sizes during page-level collection and reuse at element level, avoiding redundant recursive extraction in hot loop. Addresses @cubic-dev-ai bot review comments.

cubic-dev-ai

0 issues found across 1 file (changes from recent commits).

_{Shadow auto-approve: would not auto-approve. Auto-approval blocked by 1 unresolved issue from previous reviews.

Re-trigger cubic}

Addresses cubic-dev-ai bot P2 issue - test coverage for new helper functions: - _extract_font_sizes_from_text_obj (6 tests) - _get_representative_font_size (5 tests) - _infer_category_depth_from_font_size (8 tests) Total: 19 new unit tests covering edge cases, P1 fix scenario (closest-match logic for floating-point median), and integration scenarios. Resolves test coverage blocker for PR Unstructured-IO#4369. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cubic-dev-ai

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="unstructured/partition/pdf.py">

<violation number="1" location="unstructured/partition/pdf.py:576">
P2: Custom agent: **Enforce Pragmatic Test Coverage**

Core PDF parsing behavior was changed to infer and persist `category_depth`, but no accompanying tests are included for the new helper functions or their integration path.</violation>
</file>

<file name="test_unstructured/partition/pdf_image/test_pdfminer_utils.py">

<violation number="1" location="test_unstructured/partition/pdf_image/test_pdfminer_utils.py:48">
P2: New `_make_char_with_bbox` helper accepts bbox parameters but never applies them to the `LTChar` instance, so all font-size tests relying on it do not exercise the intended height-driven behavior.</violation>
</file>

_{Shadow auto-approve: would not auto-approve because issues were found.
Tip: Review your code locally with the cubic CLI to iterate faster.

Fix all with cubic | Re-trigger cubic}

Addresses cubic-dev-ai bot P2 issue - _make_char_with_bbox now properly sets x0, y0, x1, y1 attributes on the LTChar instance so font-size tests exercise the intended height-driven behavior (y1 - y0). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cubic-dev-ai

0 issues found across 1 file (changes from recent commits).

_{Shadow auto-approve: would not auto-approve. Auto-approval blocked by 1 unresolved issue from previous reviews.

Re-trigger cubic}

Addresses cubic-dev-ai bot unresolved issue - adds integration test that verifies partition_pdf() correctly infers and assigns category_depth to Title elements based on font size hierarchy in the actual PDF processing flow. Tests full integration of helper functions in real PDF partition pipeline. Resolves test coverage blocker at pdf.py:576. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cubic-dev-ai

0 issues found across 1 file (changes from recent commits).

_{Shadow auto-approve: would not auto-approve. Auto-approval blocked by 1 unresolved issue from previous reviews.

Re-trigger cubic}

ylcnymn · 2026-06-10T00:42:51Z

@cubic-dev-ai please re-review this PR - all test coverage has been added (19 unit tests + 1 integration test)

cubic-dev-ai · 2026-06-10T00:42:58Z

@cubic-dev-ai please re-review this PR - all test coverage has been added (19 unit tests + 1 integration test)

@ylcnymn I have started the AI code review. It will take a few minutes to complete.

cubic-dev-ai

1 issue found across 2 files

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="unstructured/partition/pdf.py">

<violation number="1" location="unstructured/partition/pdf.py:576">
P2: Custom agent: **Enforce Pragmatic Test Coverage**

Core PDF parsing behavior was changed to infer and persist `category_depth`, but no accompanying tests are included for the new helper functions or their integration path.</violation>
</file>

_{Shadow auto-approve: would not auto-approve because issues were found.

Fix all with cubic | Re-trigger cubic}

Addresses cubic-dev-ai bot P2 issue at pdf.py:514 - font size pre-pass now recursively collects from all text objects including nested containers (e.g., text inside LTFigure). This ensures complete page histogram for accurate heading hierarchy inference. Added recursive helper function to traverse all nested containers and collect font sizes comprehensively. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cubic-dev-ai

0 issues found across 1 file (changes from recent commits).

_{Shadow auto-approve: would not auto-approve. Auto-approval blocked by 1 unresolved issue from previous reviews.

Re-trigger cubic}

ylcnymn · 2026-06-10T01:16:17Z

@maintainers - All cubic-dev-ai issues have been addressed across 4 commits:

Test coverage: 19 unit tests + 1 integration test (commit 70263b3)
Bbox helper fix: Coordinates applied to LTChar (commit 3398675)
Integration test: Full partition_pdf flow tested (commit 8602795)
Nested containers fix: Recursive font collection (commit 273cb3c)

Bot reports "0 issues found" in each commit review, but auto-approve is blocked by stale "1 unresolved issue from previous reviews" - appears to be a bot cache/logic issue.

All test coverage and code quality issues have been resolved. PR is ready for manual review and merge.

Summary: 20 total tests added, 4 bug fixes applied, all bot-identified issues addressed.

cubic-dev-ai Bot reviewed Jun 9, 2026

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Comment thread test_unstructured/partition/pdf_image/test_pdfminer_utils.py

cubic-dev-ai Bot reviewed Jun 10, 2026

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Comment thread unstructured/partition/pdf.py Outdated

cubic-dev-ai Bot reviewed Jun 10, 2026

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ylcnymn commented Jun 10, 2026

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ylcnymn commented Jun 9, 2026 •

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