fix(lfx): preserve document metadata during conversion

[tandede]

Summary

• Copy a LangChain Document's metadata before adding its page content to the converted Data object.
• Add regression coverage proving that conversion does not modify an existing metadata text value on the source document.

Problem

Data.from_document() assigned document.metadata directly to a local variable and then wrote the page content into its text key. That write mutated the input Document, overwriting an existing metadata value or adding a new key as a side effect. Callers that reuse the original document after conversion therefore observe changed metadata.

The reverse conversion already copies Data.data before removing its text field. This change applies the same non-mutating boundary to from_document(). The converted Data output is unchanged; only the source document is preserved.

A shallow copy is sufficient because the conversion only writes one top-level key.

Validation

• Verified the regression test fails before the fix because document.metadata["text"] changes from "Metadata text" to "Doc content".
• uv run --isolated --package lfx pytest src/lfx/tests/unit/test_data_class.py src/lfx/tests/unit/schema src/lfx/tests/unit/helpers -q — 392 passed, 1 skipped.
• Ruff formatting and lint checks pass for both changed files.
• uv run --isolated --package lfx lfx --help completes successfully.

Summary by CodeRabbit

• Bug Fixes
  • Improved document conversion to preserve the original metadata.
  • Ensured metadata remains intact when it includes a key matching the document’s content field.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: 30b9a780-59fa-474a-a1ad-d7a8d8faf6ec

📥 Commits

Reviewing files that changed from the base of the PR and between 1655191 and 8cf3bd4.

📒 Files selected for processing (2)

• src/lfx/src/lfx/schema/data.py
• src/lfx/tests/unit/test_data_class.py

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Walkthrough

JSON.from_document now copies document metadata before adding page content. The unit test verifies converted content and metadata while confirming that the source Document.metadata remains unchanged.

Changes

Document conversion

Layer / File(s)	Summary
Metadata copy and conversion validation src/lfx/src/lfx/schema/data.py, src/lfx/tests/unit/test_data_class.py	from_document copies metadata before adding the text field. The test verifies converted content and metadata and confirms that the original metadata is preserved.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 8cf3b

This change prevents document metadata from being mutated during conversion while preserving the converted output; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: ogabrielluiz

🚥 Pre-merge checks | ✅ 8 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (8 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preserving document metadata during conversion.
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.
Test Coverage For New Implementations	✅ Passed	The PR adds regression coverage in test_data_class.py; it verifies converted text/metadata and preserves a source text metadata value, matching the changed from_document behavior.
Test Quality And Coverage	✅ Passed	The pytest regression test checks converted text and metadata, and verifies the source metadata remains unchanged when its text key conflicts; this directly covers the changed behavior.
Test File Naming And Structure	✅ Passed	The changed test is in the unit directory, uses the pytest-discovered test_.py/test_ pattern, and covers conversion output plus preservation of conflicting metadata; frontend and integration rule...
Excessive Mock Usage Warning	✅ Passed	The changed test uses a real LangChain Document and Data conversion. It adds no Mock, MagicMock, patch, or monkeypatch usage, so no excessive mocking is introduced.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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