feat: can set severity and filter duplicate class warnings.

src/functionalTest/groovy/com/autonomousapps/jvm/DuplicateClasspathSpec.groovy

@@ -27,12 +27,12 @@ final class DuplicateClasspathSpec extends AbstractJvmSpec {
 
     then:
     assertThat(result.task(':consumer:compileJava').outcome).isEqualTo(TaskOutcome.FAILED)
-//    assertThat(gradleProject.rootDir.toPath().resolve('consumer/build.gradle').text).contains(
-//      '''\
-//        dependencies {
-//          implementation project(':producer-2')
-//        }'''.stripIndent()
-//    )
+    //    assertThat(gradleProject.rootDir.toPath().resolve('consumer/build.gradle').text).contains(
+    //      '''\
+    //        dependencies {
+    //          implementation project(':producer-2')
+    //        }'''.stripIndent()
+    //    )
 
     where:
     gradleVersion << [GRADLE_LATEST]
@@ -71,6 +71,57 @@ final class DuplicateClasspathSpec extends AbstractJvmSpec {
     gradleVersion << [GRADLE_LATEST]
   }
 
+  def "buildHealth reports filters duplicates (#gradleVersion)"() {
+    given:
+    def project = new DuplicateClasspathProject('com/example/producer/Producer$Inner')
+    gradleProject = project.gradleProject
+
+    when:
+    def result = buildAndFail(gradleVersion, gradleProject.rootDir, 'buildHealth')
+
+    then:
+    assertThat(result.output).contains(
+      '''\
+        Warnings
+        Some of your classpaths have duplicate classes, which means the compile and runtime behavior can be sensitive to the classpath order.
+
+        Source set: main
+        \\--- compile classpath
+             \\--- com/example/producer/Producer is provided by multiple dependencies: [:producer-1, :producer-2]
+        \\--- runtime classpath
+             \\--- com/example/producer/Producer is provided by multiple dependencies: [:producer-1, :producer-2]'''
+        .stripIndent()
+    )
+
+    and:
+    assertAbout(buildHealth())
+      .that(project.actualProjectAdvice())
+      .isEquivalentIgnoringModuleAdviceAndWarnings(project.expectedProjectAdvice)
+
+    where:
+    gradleVersion << [GRADLE_LATEST]
+  }
+
+  def "buildHealth reports ignores duplicates (#gradleVersion)"() {
+    given:
+    def project = new DuplicateClasspathProject(null, 'ignore')
+    gradleProject = project.gradleProject
+
+    when:
+    def result = buildAndFail(gradleVersion, gradleProject.rootDir, 'buildHealth')
+
+    then:
+    assertThat(result.output).doesNotContain('Warnings')
+
+    and:
+    assertAbout(buildHealth())
+      .that(project.actualProjectAdvice())
+      .isEquivalentIgnoringModuleAdviceAndWarnings(project.expectedProjectAdvice)
+
+    where:
+    gradleVersion << [GRADLE_LATEST]
+  }
+
   @PendingFeature(reason = "This feature was reverted")
   def "can report on which of the duplicates is needed for binary compatibility (#gradleVersion)"() {
     given:

src/functionalTest/groovy/com/autonomousapps/jvm/projects/DuplicateClasspathProject.groovy

@@ -13,26 +13,17 @@ final class DuplicateClasspathProject extends AbstractProject {
 
   final GradleProject gradleProject
 
-  DuplicateClasspathProject() {
-    this.gradleProject = build()
+  DuplicateClasspathProject(String filter = null, String severity = null) {
+    this.gradleProject = build(filter, severity)
   }
 
-  private GradleProject build() {
+  private GradleProject build(String filter, String severity) {
+    def configuration = new DagpConfiguration(filter, severity).toString()
+
     return newGradleProjectBuilder()
       .withRootProject { r ->
         r.withBuildScript { bs ->
-          bs.withGroovy(
-            '''\
-              dependencyAnalysis {
-                issues {
-                  all {
-                    onAny {
-                      severity 'fail'
-                    }
-                  }
-                }
-              }'''.stripIndent()
-          )
+          bs.withGroovy(configuration)
         }
       }
     // :consumer uses the Producer class.
@@ -187,4 +178,43 @@ final class DuplicateClasspathProject extends AbstractProject {
     emptyProjectAdviceFor(':producer-1'),
     emptyProjectAdviceFor(':producer-2'),
   ]
+
+  static class DagpConfiguration {
+
+    private final String filter
+    private final String severity
+
+    DagpConfiguration(String filter, String severity) {
+      this.filter = filter
+      this.severity = severity
+    }
+
+    @Override
+    String toString() {
+      def builder = new StringBuilder()
+      builder.append('dependencyAnalysis {\n')
+      builder.append('  issues {\n')
+      builder.append('    all {\n')
+      builder.append('      onAny {\n')
+      builder.append('        severity \'fail\'\n')
+      builder.append('      }\n')
+
+      if (filter || severity) {
+        builder.append('      onDuplicateClassWarnings {\n')
+        if (severity) {
+          builder.append("        severity \'$severity\'\n")
+        }
+        if (filter) {
+          builder.append("        exclude \'$filter\'\n")
+        }
+        builder.append('      }\n')
+      }
+
+      builder.append('    }\n')
+      builder.append('  }\n')
+      builder.append('}')
+
+      return builder.toString()
+    }
+  }
 }

src/main/kotlin/com/autonomousapps/extension/IssueHandler.kt

@@ -65,6 +65,10 @@ abstract class IssueHandler @Inject constructor(
     return globalDslService.unusedAnnotationProcessorsIssueFor(projectPath)
   }
 
+  internal fun onDuplicateClassWarnings(projectPath: String): List<Provider<Behavior>> {
+    return globalDslService.onDuplicateClassWarnings(projectPath)
+  }
+
   internal fun redundantPluginsIssueFor(projectPath: String): Provider<Behavior> {
     return globalDslService.redundantPluginsIssueFor(projectPath)
   }

src/main/kotlin/com/autonomousapps/extension/ProjectIssueHandler.kt

@@ -20,7 +20,15 @@ import javax.inject.Inject
  *       ignoreSourceSet(...)
  *
  *       // Specify severity and exclude rules for all types of dependency violations.
- *       onAny { ... }
+ *       onAny {
+ *         severity(<"fail"|"warn"|"ignore">)
+ *
+ *         // using version catalog accessors
+ *         exclude(libs.guava, ...)
+ *
+ *         // using basic string coordinates
+ *         exclude("com.google.guava:guava", ...)
+ *       }
  *
  *       // Specify severity and exclude rules for unused dependencies.
  *       onUnusedDependencies { ... }
@@ -47,8 +55,15 @@ import javax.inject.Inject
  *
  *       // Specify severity and exclude rules for module structure advice.
  *       onModuleStructure {
- *         severity(<'fail'|'warn'|'ignore'>)
- *         exclude('android')
+ *         severity(<"fail"|"warn"|"ignore">)
+ *         exclude("android")
+ *       }
+ *
+ *       onDuplicateClassWarnings {
+ *          severity(<"fail"|"warn"|"ignore">)
+ *
+ *          // Fully-qualified class reference to exclude, slash- or dot-delimited
+ *          exclude("org/jetbrains/annotations/NotNull", "org.jetbrains.annotations.Nullable")
  *       }
  *     }
  *   }
@@ -76,6 +91,7 @@ abstract class ProjectIssueHandler @Inject constructor(
   internal val runtimeOnlyIssue = objects.newInstance<Issue>()
   internal val redundantPluginsIssue = objects.newInstance<Issue>()
   internal val moduleStructureIssue = objects.newInstance<Issue>()
+  internal val duplicateClassWarningsIssue = objects.newInstance<Issue>()
 
   internal val ignoreSourceSets = objects.setProperty<String>()
 
@@ -125,4 +141,8 @@ abstract class ProjectIssueHandler @Inject constructor(
   fun onModuleStructure(action: Action<Issue>) {
     action.execute(moduleStructureIssue)
   }
+
+  fun onDuplicateClassWarnings(action: Action<Issue>) {
+    action.execute(duplicateClassWarningsIssue)
+  }
 }

src/main/kotlin/com/autonomousapps/internal/advice/SeverityHandler.kt

@@ -2,14 +2,15 @@
 // SPDX-License-Identifier: Apache-2.0
 package com.autonomousapps.internal.advice
 
-import com.autonomousapps.model.PluginAdvice
 import com.autonomousapps.extension.Behavior
 import com.autonomousapps.extension.Fail
 import com.autonomousapps.internal.DependencyScope
 import com.autonomousapps.internal.utils.filterToSet
 import com.autonomousapps.internal.utils.lowercase
 import com.autonomousapps.model.Advice
+import com.autonomousapps.model.DuplicateClass
 import com.autonomousapps.model.ModuleAdvice
+import com.autonomousapps.model.PluginAdvice
 import com.autonomousapps.model.Advice as DependencyAdvice
 
 /** Given the set of all behaviors, determine whether the analysis should fail the build. */
@@ -20,20 +21,33 @@ internal class SeverityHandler(
   private val incorrectConfigurationBehavior: Pair<Behavior, List<Behavior>>,
   private val compileOnlyBehavior: Pair<Behavior, List<Behavior>>,
   private val unusedProcsBehavior: Pair<Behavior, List<Behavior>>,
+  private val duplicateClassWarningsBehavior: Pair<Behavior, List<Behavior>>,
   private val redundantPluginsBehavior: Behavior,
   private val moduleStructureBehavior: Behavior,
 ) {
 
   fun shouldFailDeps(advice: Set<DependencyAdvice>): Boolean {
-    return shouldFailFor(anyBehavior, advice) ||
-      shouldFailFor(unusedDependenciesBehavior, advice.filterToSet { it.isRemove() }) ||
-      shouldFailFor(usedTransitiveDependenciesBehavior, advice.filterToSet { it.isAdd() }) ||
-      shouldFailFor(incorrectConfigurationBehavior, advice.filterToSet { it.isChange() }) ||
-      shouldFailFor(compileOnlyBehavior, advice.filterToSet { it.isCompileOnly() }) ||
-      shouldFailFor(unusedProcsBehavior, advice.filterToSet { it.isProcessor() })
+    return shouldFailForAdvice(anyBehavior, advice) ||
+      shouldFailForAdvice(unusedDependenciesBehavior, advice.filterToSet { it.isRemove() }) ||
+      shouldFailForAdvice(usedTransitiveDependenciesBehavior, advice.filterToSet { it.isAdd() }) ||
+      shouldFailForAdvice(incorrectConfigurationBehavior, advice.filterToSet { it.isChange() }) ||
+      shouldFailForAdvice(compileOnlyBehavior, advice.filterToSet { it.isCompileOnly() }) ||
+      shouldFailForAdvice(unusedProcsBehavior, advice.filterToSet { it.isProcessor() })
+  }
+
+  fun shouldFailPlugins(pluginAdvice: Set<PluginAdvice>): Boolean {
+    return (redundantPluginsBehavior.isFail() || anyBehavior.first.isFail()) && pluginAdvice.isNotEmpty()
+  }
+
+  fun shouldFailModuleStructure(moduleAdvice: Set<ModuleAdvice>): Boolean {
+    return (moduleStructureBehavior.isFail() || anyBehavior.first.isFail()) && ModuleAdvice.isNotEmpty(moduleAdvice)
+  }
+
+  fun shouldFailDuplicateClasses(duplicateClasses: Set<DuplicateClass>): Boolean {
+    return shouldFailForDuplicateClasses(duplicateClassWarningsBehavior, duplicateClasses)
   }
 
-  private fun shouldFailFor(
+  private fun shouldFailForAdvice(
     spec: Pair<Behavior, List<Behavior>>,
     advice: Set<DependencyAdvice>,
   ): Boolean {
@@ -50,7 +64,6 @@ internal class SeverityHandler(
         b.sourceSetName == from || b.sourceSetName == to
       }
 
-
       // Looking for a match between sourceSet-specific behavior and advice.
       var shouldFail = false
       behaviors.forEach { b ->
@@ -71,12 +84,37 @@ internal class SeverityHandler(
     return advice.any(bySourceSets) || (spec.first.isFail() && globalAdvice.isNotEmpty())
   }
 
-  fun shouldFailPlugins(pluginAdvice: Set<PluginAdvice>): Boolean {
-    return (redundantPluginsBehavior.isFail() || anyBehavior.first.isFail()) && pluginAdvice.isNotEmpty()
-  }
+  private fun shouldFailForDuplicateClasses(
+    spec: Pair<Behavior, List<Behavior>>,
+    duplicateClasses: Set<DuplicateClass>,
+  ): Boolean {
+    // Seed the "global" warnings with the set of all possible warnings. Later on we'll drain this set as elements of it
+    // are  "consumed" by sourceSet-specific behaviors.
+    val globalAdvice = duplicateClasses.toMutableSet()
 
-  fun shouldFailModuleStructure(moduleAdvice: Set<ModuleAdvice>): Boolean {
-    return (moduleStructureBehavior.isFail() || anyBehavior.first.isFail()) && ModuleAdvice.isNotEmpty(moduleAdvice)
+    val bySourceSets: (DuplicateClass) -> Boolean = { d ->
+      // These are the custom behaviors, if any, associated with the source sets represented by this warning.
+      val behaviors = spec.second.filter { b ->
+        b.sourceSetName == DependencyScope.sourceSetName(d.classpathName)
+      }
+
+      // Looking for a match between sourceSet-specific behavior and warning.
+      var shouldFail = false
+      behaviors.forEach { b ->
+        val s = b.sourceSetName.lowercase()
+        val from = d.classpathName.lowercase().startsWith(s)
+
+        if (from) {
+          shouldFail = shouldFail || b.isFail()
+          globalAdvice.remove(d)
+        }
+      }
+
+      shouldFail
+    }
+
+    // If all advice is sourceSet-specific, then globalAdvice will be empty.
+    return duplicateClasses.any(bySourceSets) || (spec.first.isFail() && globalAdvice.isNotEmpty())
   }
 
   private fun Behavior.isFail(): Boolean = this is Fail

src/main/kotlin/com/autonomousapps/model/DuplicateClass.kt

@@ -1,5 +1,6 @@
 package com.autonomousapps.model
 
+import com.autonomousapps.extension.Behavior
 import com.autonomousapps.internal.utils.LexicographicIterableComparator
 import com.autonomousapps.model.declaration.Variant
 import com.squareup.moshi.JsonClass
@@ -25,6 +26,12 @@ data class DuplicateClass(
     const val RUNTIME_CLASSPATH_NAME = "runtime"
   }
 
+  private val dotty = className.replace('/', '.')
+
+  internal fun containsMatchIn(behavior: Behavior): Boolean {
+    return behavior.filter.contains(className) || behavior.filter.contains(dotty)
+  }
+
   override fun compareTo(other: DuplicateClass): Int {
     return compareBy(DuplicateClass::variant)
       .thenBy(DuplicateClass::classpathName)

src/main/kotlin/com/autonomousapps/services/GlobalDslService.kt

@@ -238,6 +238,10 @@ abstract class GlobalDslService @Inject constructor(
     return issuesFor(projectPath) { it.unusedAnnotationProcessorsIssue }
   }
 
+  internal fun onDuplicateClassWarnings(projectPath: String): List<Provider<Behavior>> {
+    return issuesFor(projectPath) { it.duplicateClassWarningsIssue }
+  }
+
   internal fun redundantPluginsIssueFor(projectPath: String): Provider<Behavior> {
     return overlay(all.redundantPluginsIssue, projects.findByName(projectPath)?.redundantPluginsIssue)
   }

src/main/kotlin/com/autonomousapps/subplugin/ProjectPlugin.kt

@@ -1035,6 +1035,7 @@ internal class ProjectPlugin(private val project: Project) {
         compileOnlyBehavior.addAll(compileOnlyIssueFor(theProjectPath))
         runtimeOnlyBehavior.addAll(runtimeOnlyIssueFor(theProjectPath))
         unusedProcsBehavior.addAll(unusedAnnotationProcessorsIssueFor(theProjectPath))
+        duplicateClassWarningsBehavior.addAll(onDuplicateClassWarnings(theProjectPath))
 
         // These don't have sourceSet-specific behaviors
         redundantPluginsBehavior.set(redundantPluginsIssueFor(theProjectPath))