Treat compile warnings as errors

pom.xml

@@ -59,10 +59,11 @@
         <version>3.14.0</version>
         <configuration>
           <release>26</release>
+          <failOnWarning>true</failOnWarning>
           <compilerArgs>
             <arg>-XDcompilePolicy=simple</arg>
             <arg>--should-stop=ifError=FLOW</arg>
-            <arg>-Xplugin:ErrorProne</arg>
+            <arg>-Xplugin:ErrorProne -XepExcludedPaths:.*/target/generated-(test-)?sources/.*</arg>
           </compilerArgs>
           <annotationProcessorPaths>
             <path>
@@ -95,6 +96,9 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>
         <version>3.12.0</version>
+        <configuration>
+          <failOnWarnings>true</failOnWarnings>
+        </configuration>
         <executions>
           <execution>
             <id>attach-javadocs</id>

src/test/java/com/google/acai/AcaiTest.java

@@ -313,6 +313,7 @@ MethodCalls incrementAfterTest() {
   }
 
   private static class TestWithUnsatisfiedBinding {
+    @SuppressWarnings("unused") // Fixture: injection should fail before this is read.
     @Inject @TestBindingAnnotation ExampleTest unsatisfiedBinding;
   }
 
@@ -342,6 +343,8 @@ protected void configureTestingServices() {
     }
   }
 
+  // Fixture: existence of the non-zero-arg constructor is what the test verifies.
+  @SuppressWarnings("unused")
   private static class ModuleWithoutZeroArgumentConstructor extends AbstractModule {
     ModuleWithoutZeroArgumentConstructor(String argument) {
       // No-op.
@@ -381,6 +384,7 @@ String provideValueAndAddTearDown(TearDownAccepter tearDownAccepter) {
   }
 
   private static class TearDownAccepterTest {
+    @SuppressWarnings("unused") // Forces @Provides to fire so the teardown is registered.
     @Inject @TestBindingAnnotation String injected;
   }
 

src/test/java/com/google/acai/GuiceberryCompatibilityModuleTest.java

@@ -131,21 +131,19 @@ public void evaluate() {
   @Test
   public void testWrapperExceptionPropagated() {
     FakeTestClass test = new FakeTestClass();
-
-    assertThrows(
-        TestException.class,
-        () ->
-            new Acai(ThrowingWrapperModule.class)
-                .apply(
-                    new Statement() {
-                      @Override
-                      public void evaluate() {
-                        assertWithMessage("Test should not run when TestWrapper throws").fail();
-                      }
-                    },
-                    frameworkMethod,
-                    test)
-                .evaluate());
+    Statement statement =
+        new Acai(ThrowingWrapperModule.class)
+            .apply(
+                new Statement() {
+                  @Override
+                  public void evaluate() {
+                    assertWithMessage("Test should not run when TestWrapper throws").fail();
+                  }
+                },
+                frameworkMethod,
+                test);
+
+    assertThrows(TestException.class, statement::evaluate);
   }
 
   private static class FakeTestClass {

src/test/java/com/google/acai/TestScopeTest.java

@@ -253,6 +253,7 @@ private static class FakeTestClassWithProvider {
   private static class MyTestScopedClass {}
 
   private static class InvalidTestingService implements TestingService {
+    @SuppressWarnings("unused") // Fixture: @TestScoped injected into a TestingService is rejected.
     @Inject MyTestScopedClass testScoped;
   }
 

src/test/java/com/google/acai/TestingServiceManagerTest.java

@@ -150,6 +150,7 @@ private void incrementPrivateBeforeTestCount() {
     }
 
     @BeforeTest
+    @SuppressWarnings("unused") // Parameter is the whole point: makes the method ineligible.
     private void incrementBeforeTestWithParameterCount(int someParameter) {
       beforeTestWithParameterCount++;
     }