Roave Backward Compatibility Check: Ensuring PHP Stability (with examples)

Roave’s Backward Compatibility Check is an essential command-line tool for PHP developers who wish to maintain the stability and consistency of API contracts over time. This tool helps developers by identifying backward compatibility breaks between different versions of a PHP library, ensuring that changes do not inadvertently disrupt or degrade the functionality available to end-users. Leveraging this tool can yield a profound impact on maintaining user trust and seamless software updates.

Use Case 1: Check for Breaking Changes Since the Last Tag

Code:

roave-backward-compatibility-check

Motivation:

Developers often release multiple versions of their PHP libraries. Over time, these updates can introduce changes that might break backward compatibility. This use case helps developers validate that the current state of their library still upholds the promises made by the last officially tagged release. By checking for breaking changes since the last tag, developers can quickly identify if any modifications have introduced breaking changes to the API, allowing them to address issues before a new release is made public.

Explanation:

• The command roave-backward-compatibility-check runs a default comparison between the latest tagged release and the current codebase. It does not require any additional options as it automatically assumes interest in the latest state vs. the last stable state comparison.

Example Output:

[BC] REMOVED: Property LibraryClass::$oldProperty has been removed.
[BC] CHANGED: Method LibraryClass::existingMethod() no longer has parameter $param as optional.

Use Case 2: Check for Breaking Changes Since a Specific Tag

Code:

roave-backward-compatibility-check --from=git_reference

Motivation:

At times, developers want to compare potential backward compatibility breaks from a specific point in history rather than the latest tag. This use case is particularly relevant for scenarios where branching strategies or custom iterations happen, necessitating checks from past specific tagged commits. This approach ensures flexibility in backward comparison, allowing developers to choose any historical reference point as the baseline.

Explanation:

• --from=git_reference: This argument specifies the starting reference point for the backward compatibility check. git_reference represents a specific tag, commit hash, or branch that the developer wishes to compare against the current state of the code.

Example Output:

No backward-incompatible changes detected between the specified versions.

Use Case 3: Check for Breaking Changes Between the Last Tag and a Specific Reference

Code:

roave-backward-compatibility-check --to=git_reference

Motivation:

In certain scenarios, developers may wish to validate that their changes leading up to a specific commit (such as a feature branch merge) do not disrupt the backward compatibility promised by the last tag. This check is crucial for integrating larger features or refactorings, ensuring that the merge does not inadvertently introduce issues for end-users relying on the API’s stability.

Explanation:

• --to=git_reference: This argument directs the backward compatibility tool to focus on changes introduced up to a specified reference point. This provides flexibility in determining the potential impact of new developments in-progress.

Example Output:

[BC] CHANGED: Method LibraryClass::deprecatedMethod() visibility changed from public to private.

Use Case 4: Check for Breaking Changes and Output to Markdown

Code:

roave-backward-compatibility-check --format=markdown > results.md

Motivation:

Documenting backward compatibility checks is key for transparency and continuous integration workflows. Producing output in markdown format allows easier integration into project documentation or reports. This is particularly advantageous in team environments or for distributed teams where detailed records of code changes and checks can be easily shared and reviewed.

Explanation:

• --format=markdown: This option converses the results into a markdown format, which is ideal for human-readable documentation.
• > results.md: This redirection stores the command output into a file named results.md, creating a permanent record of the compatibility check results.

Example Output:

The content of results.md will be:

### Backward Compatibility Report

- **[BC] REMOVED:** Method `LibraryClass::oldFunction()` removed.
- **[BC] CHANGED:** Visibility of method `LibraryClass::newFunction()` changed from protected to private.

Conclusion:

Roave Backward Compatibility Check is an indispensable tool for PHP developers striving to manage evolution within their codebases while systematically safeguarding user expectations around existing library functionalities. Utilizing these command scenarios enables thoughtful, deliberate, and informed version management decisions.