tools: Skill for Claude Code

Enforcer Rules Skill

Add or change a rule in claude-code-enforcer, the module of custom maven-enforcer-plugin rules that guard this repository's agent-facing files. Every rule follows the same shape, so getting the shape right is most of the work.

The two-phase build (there is no shortcut)

A maven-enforcer rule must be resolvable as a JAR before the build that uses it runs, so a change to a rule needs two commands:

mvn -pl claude-code-enforcer -am install   # 1. publish the rule locally
mvn -N validate -DenforceClaudeMd          # 2. quick root-only doc check

Skipping step 1 runs the previous rule against your new expectations. The check is opt-in (claude-md-enforce profile, activated by -DenforceClaudeMd), so ordinary builds are unaffected; .github/workflows/maven.yml is the only workflow that opts in.

Anatomy of a rule

@Named("myNewRule")                                  // the pom's <myNewRule> element
public class MyNewRule extends ClaudeCodeEnforcerRule {

    private File someFile;                           // injected from the configuration

    @Override
    public void execute() throws EnforcerRuleException {
        requireDocument(someFile, "someFile");       // build-setup checks first
        String content = requireContent(someFile, "someFile");
        List<String> violations = new ArrayList<>();
        // ... collect every problem, never stop at the first ...
        report("What went wrong, in one line:", violations);
    }

    void setSomeFile(File someFile) {                // package-private setter per parameter
        this.someFile = someFile;
    }
}

Rules that check a property across every definition (skills, sub-agents, commands) extend MultiDefinitionRule instead and call forEachDefinition(...) — it already owns commandsDir / agentsDir / skillsDir traversal, where a skill is a directory holding a SKILL.md.

Rules that validate one kind of definition file by file extend DefinitionFormatRule, which owns the directory scan, the autoFix parameter and the grouped report. A subclass supplies the Naming its messages use, the directory, entriesIn(...) (the *.md files, or the subdirectories for skills), and collectEntryViolations(...) — reaching for contentOf(...) and frontMatterOf(...) / requiredFrontMatterOf(...) rather than reading and parsing again.