Ability to tune unused dependency handling per target

kotlin/internal/jvm/compile.bzl

@@ -64,9 +64,18 @@ def find_java_runtime_toolchain(ctx, target):
 def _java_info(target):
     return target[JavaInfo] if JavaInfo in target else None
 
-def _deps_artifacts(toolchains, targets):
+def _report_unused_deps(ctx, toolchains):
+    if "kt_experimental_report_unused_deps_off" in ctx.attr.tags:
+        return "off"
+    if "kt_experimental_report_unused_deps_warn" in ctx.attr.tags:
+        return "warn"
+    if "kt_experimental_report_unused_deps_error" in ctx.attr.tags:
+        return "error"
+    return toolchains.kt.experimental_report_unused_deps
+
+def _deps_artifacts(ctx, toolchains, targets):
     """Collect Jdeps artifacts if required."""
-    if not toolchains.kt.experimental_report_unused_deps == "off":
+    if not _report_unused_deps(ctx, toolchains) == "off":
         deps_artifacts = [t[JavaInfo].outputs.jdeps for t in targets if JavaInfo in t and t[JavaInfo].outputs.jdeps]
     else:
         deps_artifacts = []
@@ -320,7 +329,13 @@ def _run_merge_jdeps_action(ctx, toolchains, jdeps, outputs, deps):
         args.add("--" + f, path)
 
     args.add_all("--inputs", jdeps, omit_if_empty = True)
-    args.add("--report_unused_deps", toolchains.kt.experimental_report_unused_deps)
+    args.add("--report_unused_deps", _report_unused_deps(ctx, toolchains))
+    unused_deps_ignored_targets = [
+        tag.split(":", 1)[1]
+        for tag in ctx.attr.tags
+        if tag.startswith("kt_experimental_unused_deps_ignored_targets:")
+    ]
+    args.add_all("--unused_deps_ignored_targets", unused_deps_ignored_targets, omit_if_empty = True)
 
     mnemonic = "JdepsMerge"
     progress_message = "%s %%{label} { jdeps: %d }" % (
@@ -329,7 +344,7 @@ def _run_merge_jdeps_action(ctx, toolchains, jdeps, outputs, deps):
     )
 
     inputs = depset(jdeps)
-    if not toolchains.kt.experimental_report_unused_deps == "off":
+    if not _report_unused_deps(ctx, toolchains) == "off":
         # For sandboxing to work, and for this action to be deterministic, the compile jars need to be passed as inputs
         inputs = depset(jdeps, transitive = [depset([], transitive = [dep.transitive_compile_time_jars for dep in deps])])
 
@@ -596,7 +611,7 @@ def kt_jvm_produce_jar_actions(ctx, rule_kind):
     transitive_runtime_jars = _plugin_mappers.targets_to_transitive_runtime_jars(ctx.attr.plugins + ctx.attr.deps)
     plugins = _new_plugins_from(ctx.attr.plugins + _exported_plugins(deps = ctx.attr.deps))
 
-    deps_artifacts = _deps_artifacts(toolchains, ctx.attr.deps + ctx.attr.associates)
+    deps_artifacts = _deps_artifacts(ctx, toolchains, ctx.attr.deps + ctx.attr.associates)
 
     generated_src_jars = []
     annotation_processing = None

src/main/kotlin/io/bazel/kotlin/builder/tasks/jvm/JdepsMerger.kt

@@ -38,6 +38,7 @@ class JdepsMerger {
       OUTPUT("--output"),
       TARGET_LABEL("--target_label"),
       REPORT_UNUSED_DEPS("--report_unused_deps"),
+      UNUSED_DEPS_IGNORED_TARGETS("--unused_deps_ignored_targets"),
     }
 
     private fun readJarOwnerFromManifest(jarPath: Path): JarOwner {
@@ -63,6 +64,7 @@ class JdepsMerger {
       inputs: List<String>,
       output: String,
       reportUnusedDeps: String,
+      unusedDepsIgnoredTargets: List<String>,
     ): Int {
       val rootBuilder = Deps.Dependencies.newBuilder()
       rootBuilder.success = false
@@ -114,6 +116,7 @@ class JdepsMerger {
             .filter { it.value == Deps.Dependency.Kind.UNUSED }
             .map { it.key }
             .filter { it != label }
+            .filter { it !in unusedDepsIgnoredTargets }
 
         if (unusedLabels.isNotEmpty()) {
           ctx.info {
@@ -160,7 +163,9 @@ class JdepsMerger {
     val output = argMap.mandatorySingle(JdepsMergerFlags.OUTPUT)
     val label = argMap.mandatorySingle(JdepsMergerFlags.TARGET_LABEL)
     val reportUnusedDeps = argMap.mandatorySingle(JdepsMergerFlags.REPORT_UNUSED_DEPS)
+    val unusedDepsIgnoredTargets =
+      argMap.optional(JdepsMergerFlags.UNUSED_DEPS_IGNORED_TARGETS).orEmpty()
 
-    return merge(ctx, label, inputs, output, reportUnusedDeps)
+    return merge(ctx, label, inputs, output, reportUnusedDeps, unusedDepsIgnoredTargets)
   }
 }

src/test/kotlin/io/bazel/kotlin/builder/tasks/jvm/JdepsMergerTest.kt

@@ -204,6 +204,67 @@ class JdepsMergerTest {
     ).containsExactly(unusedKotlinDep)
   }
 
+  @Test
+  fun `unused deps report warning unless ignored`() {
+    val merger = DaggerJdepsMergerTestComponent.builder().build().jdepsMerger()
+
+    val unusedKotlinDep1 = ktJvmLibrary("kotlin_dep1")
+    val unusedKotlinDep2 = ktJvmLibrary("kotlin_dep2")
+    val kotlinJdeps = jdeps("kt.jdeps") {
+      addDependency(
+        with(Dependency.newBuilder()) {
+          kind = Dependency.Kind.UNUSED
+          path = unusedKotlinDep1
+          build()
+        },
+      )
+      addDependency(
+        with(Dependency.newBuilder()) {
+          kind = Dependency.Kind.UNUSED
+          path = unusedKotlinDep2
+          build()
+        },
+      )
+    }
+
+    val javaJdeps = jdeps("java.jdeps") {
+      addDependency(
+        with(Dependency.newBuilder()) {
+          kind = Dependency.Kind.EXPLICIT
+          path = ktJvmLibrary("java_dep")
+          build()
+        },
+      )
+    }
+
+    val mergedJdeps = out("merged.jdeps")
+
+    val result = WorkerContext.run {
+      doTask("jdepsmerge") { taskCtx ->
+        MergeJdeps(merger = merger).invoke(
+          taskCtx,
+          args {
+            input(kotlinJdeps)
+            input(javaJdeps)
+            flag(JdepsMergerFlags.TARGET_LABEL, "//foo/bar:baz")
+            flag(JdepsMergerFlags.OUTPUT, mergedJdeps)
+            flag(JdepsMergerFlags.REPORT_UNUSED_DEPS, "warn")
+            flag(JdepsMergerFlags.UNUSED_DEPS_IGNORED_TARGETS, "kotlin_dep2")
+          },
+        )
+      }
+    }
+    assertThat(result.status).isEqualTo(SUCCESS)
+    assertThat(result.log.out.toString()).contains("'remove deps kotlin_dep1' //foo/bar:baz")
+
+    val depsProto = depsProto(mergedJdeps)
+    assertThat(
+      depsProto.dependencyList
+        .filter { it.kind == Dependency.Kind.UNUSED }
+        .map { it.path },
+    ).containsExactly(unusedKotlinDep1, unusedKotlinDep2)
+  }
+
   @Test
   fun `unused deps report error`() {
     val merger = DaggerJdepsMergerTestComponent.builder().build().jdepsMerger()