[yaml] - expand jinja method

[derrickaw]

1. Fixes [Task]: YAML - update expand_jinja method #35936
2. Adds support for relative paths

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[codecov]

Codecov Report

❌ Patch coverage is 92.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.73%. Comparing base (e83a1d5) to head (064f8c2).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
sdks/python/apache_beam/yaml/yaml_transform.py	90.90%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #38547   +/-   ##
=========================================
  Coverage     58.72%   58.73%           
  Complexity     7418     7418           
=========================================
  Files          1649     1649           
  Lines        212354   212415   +61     
  Branches       6330     6330           
=========================================
+ Hits         124712   124763   +51     
- Misses        83097    83107   +10     
  Partials       4545     4545           

Flag	Coverage Δ
python	79.89% <92.50%> (+<0.01%)	⬆️

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[derrickaw]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces support for Jinja search paths and comment stripping in Beam YAML templates. Key changes include updating _BeamFileIOLoader to resolve relative paths using provided search paths and implementing strip_leading_comments to handle license headers in templates. Feedback highlights a missing shutil import in the new tests, suggests using os.path.isabs() for cross-platform path validation, and recommends avoiding bare exception handling when loading files.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the YAML pipeline templating system in Apache Beam by improving how Jinja templates are resolved and processed. It introduces a mechanism to handle relative file imports and adds robust handling for leading comments in template files, ensuring that complex YAML configurations can be modularized and parsed correctly.

Highlights

• Jinja Template Search Paths: Implemented support for relative path resolution in Jinja templates, allowing users to import macros and files from directories relative to the pipeline file.
• Comment Stripping: Added a utility to strip leading comments from YAML/Jinja templates to ensure valid parsing even when files contain license headers or other metadata at the top.
• Provider Configuration: Updated YamlProvider to accept a base path, enabling consistent file resolution for templated providers.

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[gemini-code-assist]

Code Review

This pull request enhances Beam YAML's Jinja templating by adding support for search paths and improving the handling of files with leading comments, such as license headers. It introduces a strip_leading_comments function and updates _BeamFileIOLoader to resolve relative paths across multiple directories. Feedback was provided regarding the strip_leading_comments implementation, noting that completely removing lines shifts line numbers in error messages; a suggestion was made to replace the content with blank lines to preserve the original line count for better debugging.

[github-actions]

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R: @claudevdm for label python.

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