Package org.apache.flink.tools.ci.optional

Class ShadeOptionalChecker

  • public class ShadeOptionalChecker
extends Object
    Verifies that all dependencies bundled with the shade-plugin are marked as optional in the pom. This ensures compatibility with later maven versions and in general simplifies dependency management as transitivity is no longer dependent on the shade-plugin.

    In Maven 3.3 the dependency tree was made immutable at runtime, and thus can no longer be changed by the shade plugin. The plugin would usually remove a dependency from the tree when it is being bundled (known as dependency reduction). While dependency reduction still works for the published poms (== what users consume) since it can still change the content of the final pom, while developing Flink it no longer works. This breaks plenty of things, since suddenly a bunch of dependencies are still visible to downstream modules that weren't before.

    To workaround this we mark all dependencies that we bundle as optional; this makes them non-transitive. To a downstream module, behavior-wise a non-transitive dependency is identical to a removed dependency.

    This checker analyzes the bundled dependencies (based on the shade-plugin output) and the set of dependencies (based on the dependency plugin) to detect cases where a dependency is not marked as optional as it should.

    The enforced rule is rather simple: Any dependency that is bundled, or any of its parents, must show up as optional in the dependency tree. The parent clause is required to cover cases where a module has 2 paths to a bundled dependency. If a module depends on A1/A2, each depending on B, with A1 and B being bundled, then even if A1 is marked as optional B is still shown as a non-optional dependency (because the non-optional A2 still needs it!).

    • Constructor Detail

      • ShadeOptionalChecker

        public ShadeOptionalChecker()