feat: Add default-group-optionality configuration option

[3015pavan]

This commit implements a new configuration option default-group-optionality that allows users to treat all dependency groups as optional by default.

When set to true, Poetry will only install the implicit main group by default, and other groups must be explicitly requested using --with or --only flags. This eliminates the need to mark each group as optional = true in pyproject.toml for projects with many optional dependency groups.

Changes:

• Add default-group-optionality boolean config option (default: false)
• Modify GroupCommand.non_optional_groups to respect the configuration
• Add comprehensive tests for the new functionality
• Update documentation with usage examples

Fixes #10550

Pull Request Check List

Resolves: #issue-number-here

• [x] Added tests for changed code.
• [x] Updated documentation for changed code.

Summary by Sourcery

Add a new default-group-optionality configuration option to allow treating all dependency groups as optional by default and update related command logic, documentation, and tests.

New Features:

• Introduce default-group-optionality boolean config option to toggle default optionality of dependency groups

Enhancements:

• Update GroupCommand to respect the default-group-optionality setting when determining which groups to install

Documentation:

• Document the default-group-optionality option in the configuration guide with usage examples

Tests:

• Add comprehensive tests for the new default-group-optionality behavior, including install scenarios and config commands

[sourcery-ai[bot]]

Reviewer's Guide

Introduces a new default-group-optionality boolean setting that makes all dependency groups optional by default, updates GroupCommand to respect this option, extends configuration handling and documentation, and adds tests covering the new behavior.

Class diagram for updated configuration handling (Config class)

classDiagram
    class Config {
        +bool default-group-optionality = False
        +__init__(use_environment: bool)
        +_get_normalizer(name: str)
    }

Class diagram for updated GroupCommand logic

classDiagram
    class GroupCommand {
        +non_optional_groups: set[str]
    }
    GroupCommand --> Config : uses

File-Level Changes

Change	Details	Files
Introduce default-group-optionality configuration key	Add default false value in Config.DEFAULTS Include key in boolean normalizer set Register key in config command validators	src/poetry/config/config.py src/poetry/console/commands/config.py
Update group command to honor default-group-optionality	Fetch config value in non_optional_groups Return empty non-optional set when option is enabled	src/poetry/console/commands/group_command.py
Document the default-group-optionality option	Add key description, environment variable, and examples	docs/configuration.md
Add and update tests for default-group-optionality	Update config listing and default value tests Add integration tests for install command behavior	tests/console/commands/test_config.py tests/config/test_config.py tests/console/commands/test_default_group_optionality.py

Assessment against linked issues

Issue	Objective	Addressed	Explanation
https://github.com/python-poetry/poetry/issues/10550	Implement a configuration option (e.g., tool.poetry.default-group-optionality) to allow users to set the default optionality for dependency groups.	✅
https://github.com/python-poetry/poetry/issues/10550	Ensure that when the configuration option is enabled, all dependency groups (except the implicit main group) are treated as optional by default, so that only explicitly requested groups are installed.	✅
https://github.com/python-poetry/poetry/issues/10550	Update documentation and add tests to cover the new configuration option and its behavior.	✅

Possibly linked issues

• #10550: The PR implements the default-group-optionality configuration option to allow treating all dependency groups as optional by default, as proposed in the issue.

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[3015pavan]

Hey! I saw issue #10550 and thought this would be useful. Let me know if you'd like any changes! 😊