Support multi-valued fields in rewrite and advancedrewrite plugins

[snejus]

Fix rewriting of multi-valued fields (rewrite / advancedrewrite plugins)

Bug: Both rewrite and advancedrewrite plugins assumed all field values are scalars, so list-type fields (e.g. genres) were not rewritten correctly. Additionally, only the first matching rule was ever applied to a field.

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What changed

Core logic (beetsplug/rewrite.py):

• Introduced a rewrite_value singledispatch function to handle both str and list[str] values. For lists, each element is rewritten individually.
• Extracted apply_rewrite_rules as a shared utility — now applies all matching rules in config order (previously stopped at the first match).

advancedrewrite plugin:

• Replaced its own inline rule-matching loop with a call to the shared apply_rewrite_rules, fixing list field support there too.

Behaviour change — rule application order:

Previously, only the first matching rule was applied. Now, all rules run in config order, allowing chained rewrites. For example:

rewrite:
    artist .*hendrix.*: hendrix catalog
    artist .*catalog.*: Experience catalog

This now produces "Experience catalog" instead of "hendrix catalog".

Fixes: #6515

[Copilot]

Pull request overview

Adds proper rewrite support for multi-valued (list) fields in the rewrite and advancedrewrite plugins so rules can affect fields like genres instead of being ignored.

Changes:

• Introduce apply_rewrite_rules / rewrite_value in beetsplug/rewrite.py to handle str and list values.
• Delegate advancedrewrite simple-rule rewriting to the shared helper.
• Add tests + docs + changelog entry covering list-field rewriting behavior.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
beetsplug/rewrite.py	Adds singledispatch-based rewrite helper for scalar + list values; used by template field rewriters.
beetsplug/advancedrewrite.py	Switches simple-rule path to call shared helper before advanced-query rewrites.
test/plugins/test_rewrite.py	New tests for scalar rewriting, rule order, and list-field (genres) rewriting.
test/plugins/test_advancedrewrite.py	Adds coverage for simple-rule rewriting on list fields.
docs/plugins/rewrite.rst	Documents that rewrite rules apply to matching list entries for multi-valued fields.
docs/plugins/advancedrewrite.rst	Notes parity with rewrite for list-field simple rules.
docs/changelog.rst	Adds bugfix note for multi-valued rewrite behavior.

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 70.55%. Comparing base (fd586ef) to head (2ff7887).
⚠️ Report is 7 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
beetsplug/rewrite.py	94.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6518      +/-   ##
==========================================
+ Coverage   70.40%   70.55%   +0.15%     
==========================================
  Files         148      148              
  Lines       18806    18820      +14     
  Branches     3067     3066       -1     
==========================================
+ Hits        13240    13279      +39     
+ Misses       4916     4894      -22     
+ Partials      650      647       -3     

Files with missing lines	Coverage Δ
beetsplug/advancedrewrite.py	82.43% <100.00%> (+1.35%)	⬆️
beetsplug/rewrite.py	97.95% <94.73%> (+69.38%)	⬆️

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.