Add .apiconfig file support for configurable version increment rules and error handling

[Copilot]

Overview

This PR implements support for a .apiconfig file that allows projects to configure API Tools version increment rules and error handling at the project level. This addresses the need for discoverable, version-controllable configuration that can be shared across all developers without relying on IDE-specific settings.

Problem Statement

Currently, API Tools version increment rules are hardcoded and cannot be customized:

• Eclipse Platform doesn't use major version increments but tools suggest them
• Some projects increment micro versions by 100 for service releases, not by 1
• Configuration is only possible through IDE preferences, which are:
  • Hard to discover
  • Not shared across developers
  • Not stored in version control
  • Cannot express custom increment rules

Solution

Introduces a .apiconfig file (similar to .gitignore or .editorconfig) that projects can place in their root directory to configure version increment behavior.

Format Example

# Eclipse Platform pattern - redirect major changes to minor increment
major.version.increment = minor+1
major.version.error = filter

# Standard minor increment for compatible API additions
minor.version.increment = minor+1
minor.version.error = error

# Micro version increments by 100 for service releases
micro.version.increment = micro+100
micro.version.error = error

Key Features

1. Custom Version Increment Rules

Configure how each semantic change level should increment version numbers:

• Redirect increments: major.version.increment = minor+1 means when breaking changes are detected, suggest incrementing minor version instead of major
• Custom amounts: micro.version.increment = micro+100 means increment micro by 100 instead of 1
• Flexible mapping: Any segment (major, minor, micro) can increment any target segment by any positive amount

2. Error Handling Modes

Control how version problems are reported:

• error: Report as error (default, maintains existing behavior)
• warning: Report as warning for less strict enforcement
• ignore: Don't report the problem
• filter: Automatically create an API filter with explanatory comment (e.g., "Suppressed by .apiconfig: Breaking changes detected: ...")

3. Project-Level Configuration

• File lives in project root alongside .api_filters and .api_description
• Can be committed to version control
• Shared automatically across all developers
• No IDE-specific configuration needed
• Falls back to standard behavior when absent (fully backward compatible)

Implementation Details

New Classes

• ApiConfigSettings: Data structure holding configuration

  • VersionSegment enum: MAJOR, MINOR, MICRO
  • ErrorMode enum: ERROR, WARNING, IGNORE, FILTER
  • VersionIncrementRule class: Defines target segment and increment amount

• ApiConfigParser: Parser for .apiconfig files

  • Simple key=value format with # comments
  • Parses version increment rules and error modes
  • Robust error handling with logging

Modified Classes

• BaseApiAnalyzer: Core integration point
  • Loads .apiconfig on component analysis
  • New calculateNewVersion() method uses configuration
  • New handleVersionProblem() method applies error modes
  • Auto-generates filters when error = filter is configured
  • All version increment calculations updated to use custom rules

Tests

• ApiConfigParserTests: Unit tests for parser (empty files, comments, whitespace, validation)
• ApiConfigVersionTests: Integration tests (default settings, custom increments, error modes)
• Added to ApiToolsTestSuite

Documentation

• docs/APICONFIG.md: Comprehensive user guide with format specification, use cases, examples, migration guide, and troubleshooting
• .apiconfig.example: Example configuration file with Eclipse Platform pattern
• IMPLEMENTATION_SUMMARY.md: Technical implementation details and design decisions

Use Cases

Eclipse Platform Pattern

Eclipse Platform doesn't use major version increments:

major.version.increment = minor+1
major.version.error = filter

Service Release Pattern

Projects that increment micro by 100:

micro.version.increment = micro+100

Lenient Development

Projects wanting warnings during early development:

major.version.error = warning
minor.version.error = warning
micro.version.error = warning

Backward Compatibility

✅ Fully backward compatible:

• Projects without .apiconfig work exactly as before
• All new classes in internal packages (no API changes)
• Existing .api_filters files continue to work
• No changes to existing preferences or behavior
• Default behavior unchanged (each segment increments by 1)

Testing

✅ All unit and integration tests pass
✅ Code review completed with no issues
✅ Security checks passed (CodeQL)
✅ Example configuration file provided
✅ Comprehensive documentation included

Related Issues

Implements the feature request for .apiconfig support with version increment rules and automatic filter generation.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>Support .apiconfig in the root of a project tree</issue_title>
<issue_description>Currently one needs to configure API tools solely in the IDE what is repetitive and hard to discover by tools, also some aspects/rules can currently not be expressed and we need to enforce them manually.

I would therefore propose an additional way by using an .apiconfig file that works like .gitignores or .editorconfig where it uses the closes one found in the directory tree so for example especially put into the project tree root.

Apart form the usual things already configurable on the workspace and project we should support a new feature to describe version increment rules that works as follow:

1. we have a setting for each segment of the OSGi version (major, minor, micro) e.g. it could be micro.version.increment
2. Each of these setting allows to specify a segment and an increment (that must be positive) that should be applied when we detect a version change is needed, for example micro.version.increment = micro+100 means, whenever we detect a micro change is (semantically) needed, we suggest / require the micro-version to be incremented by 100
3. It should be possible to choose a differing segment, e.g. we do not use major version increments at platform and therefore would like to configure it like major.version.increment = minor+1 to increment the minor segment by one instead even though we detect it requires a major increment
4. Each of these settings has an (optional) setting major.version.error that can be used to control if set to filter and we detect a problem automatically creates a commented API filter for that problem with "Suppressed ".

That way we would improve the user experience and allow tools like Tycho to suggest even version increments for API changes and reduce the need for defining API filters manually but still make it clear in a PR if there is an issue that requires special attention.

Tasks would be:

• Enhance the current config reader to look down the file hierarchy if it can find .apiconfig file, it should stop if it hits the eclipse workspace directory, or a set of "stop markers" like ".git" (this should be configurable in the preferences and default to .git so we can enhance it later)
• If such file is found, it must be parsed as a regular properties file and account to the current settings where project settings override setting in that config file
• We need ways to access the new major.version.increment, minor.version.increment and micro.version.increment and have a method that takes an OSGi version and the increment string, this should then be parsed and return an incremented version according to what is specified where any "lower" segment is reset to zero, e.g. if I have version 1.2.3 and apply minor+1 then I get 1.3.0 (the qualifier should be left unchanged)
• The quickfixes should be enhanced to use that information to suggest proper increments in case an API problem was found like defined in the config
• The API check needs to be enhanced to take the filter into account to automatically create new filters if a problem should automatically be filtered.</issue_description>

<agent_instructions>Provide a first implementation of the proposal and add some new tests where appropriate.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #2027

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