Support tag-based opt-in/opt-out for unused dependencies checking

Author: JonathanPerry651

src/main/java/com/google/devtools/build/lib/rules/java/JavaCompilationHelper.java

@@ -41,6 +41,7 @@
 import com.google.devtools.build.lib.concurrent.BlazeInterners;
 import com.google.devtools.build.lib.packages.RuleClass.ConfiguredTargetFactory.RuleErrorException;
 import com.google.devtools.build.lib.packages.TargetUtils;
+import com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode;
 import com.google.devtools.build.lib.rules.java.JavaConfiguration.JavaClasspathMode;
 import com.google.devtools.build.lib.rules.java.JavaPluginInfo.JavaPluginData;
 import com.google.devtools.build.lib.rules.java.JavaToolchainProvider.JspecifyInfo;
@@ -294,7 +295,7 @@ && getJavaConfiguration().experimentalEnableJspecify()
     builder.setCompressJar(true);
     builder.setExtraData(computePerPackageData(ruleContext, javaToolchain));
     builder.setStrictJavaDeps(attributes.getStrictJavaDeps());
-    builder.setUnusedDeps(getJavaConfiguration().getUnusedDeps());
+    builder.setUnusedDeps(getUnusedDepsMode());
     semantics
         .getFixDepsTool(ruleContext.getRule(), getJavaConfiguration())
         .ifPresent(builder::setFixDepsTool);
@@ -580,4 +581,20 @@ private void createLocalOptimizationAction(
   private ImmutableList<String> getJavacOpts() {
     return customJavacOpts;
   }
+
+  private StrictDepsMode getUnusedDepsMode() {
+    StrictDepsMode mode = getJavaConfiguration().getUnusedDeps();
+    if (ruleContext.getRule() != null) {
+      for (String tag : ruleContext.getRule().getRuleTags()) {
+        if (tag.equalsIgnoreCase("unused-deps:off")) {
+          return StrictDepsMode.OFF;
+        } else if (tag.equalsIgnoreCase("unused-deps:warn")) {
+          return StrictDepsMode.WARN;
+        } else if (tag.equalsIgnoreCase("unused-deps:error")) {
+          return StrictDepsMode.ERROR;
+        }
+      }
+    }
+    return mode;
+  }
 }

src/test/java/com/google/devtools/build/lib/rules/java/JavaCompileActionBuilderTest.java

@@ -299,4 +299,42 @@ public void testUnusedDepsFlagPropagation() throws Exception {
     assertThat(JavaCompileActionTestHelper.getUnusedDepsMode(action))
         .isEqualTo(com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode.ERROR);
   }
+
+  @Test
+  public void testUnusedDepsTagOptIn() throws Exception {
+    // Global unused_deps is off by default
+    scratch.file(
+        "java/com/google/test/BUILD",
+        """
+        load("@rules_java//java:defs.bzl", "java_library")
+        java_library(
+            name = "a",
+            srcs = ["A.java"],
+            tags = ["unused-deps:error"],
+        )
+        """);
+    JavaCompileAction action =
+        (JavaCompileAction) getGeneratingActionForLabel("//java/com/google/test:liba.jar");
+    assertThat(JavaCompileActionTestHelper.getUnusedDepsMode(action))
+        .isEqualTo(com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode.ERROR);
+  }
+
+  @Test
+  public void testUnusedDepsTagOptOut() throws Exception {
+    useConfiguration("--experimental_unused_deps=error");
+    scratch.file(
+        "java/com/google/test/BUILD",
+        """
+        load("@rules_java//java:defs.bzl", "java_library")
+        java_library(
+            name = "a",
+            srcs = ["A.java"],
+            tags = ["unused-deps:off"],
+        )
+        """);
+    JavaCompileAction action =
+        (JavaCompileAction) getGeneratingActionForLabel("//java/com/google/test:liba.jar");
+    assertThat(JavaCompileActionTestHelper.getUnusedDepsMode(action))
+        .isEqualTo(com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode.OFF);
+  }
 }