fix: clean up dangling references when removing empty dependency groups

[JaviMaligno]

Fixes #10590.

When a dependency group becomes empty after removing packages, it is removed from the configuration. However, references to this group in other groups' include-groups (Legacy) or include-group (PEP 735) were left dangling, causing errors.

This PR adds logic to clean up these references when a group is removed.

Summary by Sourcery

Clean up dependency group references when groups become empty after package removal to prevent dangling references in the configuration.

Bug Fixes:

• Remove include-group entries in PEP 735 dependency-groups that point to groups removed due to becoming empty.
• Remove include-groups entries in legacy [tool.poetry.group] sections that reference groups removed due to becoming empty.
• Ensure empty dependencies sections are removed before deleting groups, avoiding stray empty tables in the configuration.

Tests:

• Adjust remove command tests to cover cleanup of dangling group references and existence checks for remaining groups.

[sourcery-ai[bot]]

Reviewer's Guide

This PR ensures that when dependency groups become empty and are removed, any references to those groups in other groups’ include directives (both PEP 735 and legacy formats) are also cleaned up, and adjusts tests to match the new behavior and avoid key errors on partially-removed groups.

Class diagram for updated remove command group cleanup logic

classDiagram
    class RemoveCommand {
        +handle() int
        -_remove_packages(packages, standard_section, poetry_section, group_name) set
        -_remove_references_to_group(group_name str, content dict_str_Any) void
    }

    class TomlContent {
        +tool_poetry_group map
        +dependency_groups map
    }

    RemoveCommand --> TomlContent : modifies

Flow diagram for _remove_references_to_group cleanup behavior

flowchart TD
    A[Start _remove_references_to_group] --> B[Input group_name, content]
    B --> C{content has dependency-groups?}
    C -->|No| F
    C -->|Yes| D[Iterate each group_content in content.dependency-groups.values]
    D --> E{group_content is list?}
    E -->|No| D
    E -->|Yes| G[Collect items where item is dict and item.include-group == group_name]
    G --> H[Remove collected items from group_content]
    H --> D
    D --> F[Get poetry_content = content.tool.poetry]

    F --> I{poetry_content has group?}
    I -->|No| Z[End]
    I -->|Yes| J[Iterate each group_content in poetry_content.group.values]
    J --> K{group_content has include-groups?}
    K -->|No| J
    K -->|Yes| L{group_name in group_content.include-groups?}
    L -->|No| P{include-groups empty?}
    L -->|Yes| M[Remove group_name from include-groups]
    M --> P{include-groups empty?}
    P -->|Yes| Q[Delete include-groups key]
    P -->|No| J
    Q --> J
    J --> Z[End]

File-Level Changes

Change	Details	Files
Clean up dangling references when removing an empty group in the new [dependency-groups] table.	Introduce a helper method to remove references to a group from PEP 735 dependency-groups and legacy tool.poetry.group include-groups declarations. Iterate over dependency-groups entries and remove items whose include-group matches the removed group name, skipping non-list entries. After removal, leave dependency-groups entries in place; only the group being removed is deleted from groups_content.	src/poetry/console/commands/remove.py
Ensure legacy [tool.poetry.group.] groups clean up both dependencies and cross-group references when they become empty.	Capture the group’s dependencies mapping before removal to determine whether it is empty after package removal. If the dependencies section becomes empty, delete only the dependencies key first, then, if the entire group table is empty, remove the group and call the helper to strip references to it from other groups. Apply the same reference cleanup when groups in the top-level [dependency-groups] table become empty and are removed.	src/poetry/console/commands/remove.py
Relax and harden tests to reflect the new behavior and partial group presence during removal.	Guard the assertion about foo being absent from bar’s dependencies with checks that group and bar still exist in the content structure. Use nested get calls for the baz assertion to avoid KeyError if group or bar was removed while still confirming that baz is not listed as a dependency. Keep existing structural assertions that the bar group section is fully removed from the serialized TOML.	tests/console/commands/test_remove.py

Assessment against linked issues

Issue	Objective	Addressed	Explanation
https://github.com/python-poetry/poetry/issues/10590	When removing an empty dependency group, remove any PEP 735 [dependency-groups] entries that reference that group via include-group to avoid dangling references.	✅
https://github.com/python-poetry/poetry/issues/10590	When removing an empty dependency group, remove any legacy [tool.poetry.group.<name>] references to that group via include-groups to avoid dangling references.	✅

Possibly linked issues

• #10590: PR implements logic to remove include-group/include-groups references when an empty dependency group is removed, fixing failures.

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[JaviMaligno]

Feedback Addressed

I've pushed a new commit that addresses the review feedback:

1. PEP 735 empty list cleanup (Sourcery + @radoering)

The _remove_references_to_group method now cleans up groups in [dependency-groups] that become empty after their include-group references are removed. This normalizes the behavior with the legacy [tool.poetry.group.<name>] path.

Key change: Added logic to track and remove groups that become empty due to include-group cleanup, while ensuring we don't prematurely delete the target group itself (which is handled by the caller).

2. Added test for reference cleanup (@radoering)

Added test_remove_group_cleans_up_include_group_references which tests:

• When a group is removed, include-group references to it in other groups are cleaned up
• Groups that become empty after their include-group references are removed are also deleted
• Tests both PEP 735 and legacy formats

3. Strengthened test assertions (Sourcery)

Updated test_remove_does_not_keep_empty_groups to explicitly assert assert "group" not in content instead of the conditional check, making the expected behavior clear.

All 23 tests in test_remove.py pass.