MetricProvider

Extension point for contributing a custom metric to Aalekh.

Custom rules (rules { custom(...) }) let you enforce structure; a MetricProvider lets you measure it. Implement this interface, register it with the JDK java.util.ServiceLoader mechanism (a META-INF/services/com.aalekh.aalekh.analysis.spi.MetricProvider file listing your class), and put the jar on the plugin's runtime classpath - the same classpath used for custom rules (a buildscript { dependencies { classpath(...) } } entry, or an includeBuild composite). The aalekhMetrics task then discovers every provider automatically and writes their values to aalekh-custom-metrics.json / .md.

A provider is a pure function of the graph: given a ModuleDependencyGraph it returns numbers. It must not touch the filesystem, the network, or the Gradle API - the graph carries everything analysis is allowed to see. A provider that throws is skipped and reported in the run's failures; it never breaks the build.

class LeafRatioMetric : MetricProvider {
    override val id = "leaf-ratio"
    override val displayName = "Leaf module ratio"
    override val description = "Share of modules that nothing depends on."
    override val unit = "%"
    override fun compute(graph: ModuleDependencyGraph): MetricContribution {
        val leaves = graph.modules.count { m -> graph.edges.none { it.to == m.path && !it.isTest } }
        val ratio = if (graph.modules.isEmpty()) 0.0 else leaves * 100.0 / graph.modules.size
        return MetricContribution(systemValue = ratio)
    }
}