Test on JDK 27 EA

.github/workflows/continuous-integration.yml

@@ -21,7 +21,12 @@ jobs:
     steps:
       - name: Check out NullAway sources
         uses: actions/checkout@v6
-      - name: 'Set up JDKs'
+      - name: 'Set up JDK 27 EA from jdk.java.net'
+        uses: oracle-actions/setup-java@v1
+        with:
+          website: jdk.java.net
+          release: 27
+      - name: 'Set up Default JDK'
         uses: actions/setup-java@v5
         with:
           java-version: 25

buildSrc/src/main/groovy/nullaway.java-test-conventions.gradle

@@ -78,7 +78,7 @@ test {
 }
 
 // Tasks for testing on other JDK versions; see https://jakewharton.com/build-on-latest-java-test-through-lowest-java/
-[21, 26].each { majorVersion ->
+[21, 26, 27].each { majorVersion ->
     def jdkTest = tasks.register("testJdk$majorVersion", Test) {
         javaLauncher = javaToolchains.launcherFor {
             languageVersion = JavaLanguageVersion.of(majorVersion)

jar-infer/jar-infer-lib/build.gradle

@@ -50,4 +50,8 @@ tasks.withType(JavaCompile).configureEach {
     options.compilerArgs += "--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED"
 }
 
+tasks.getByName('testJdk27').configure {
+    // Won't work until WALA supports JDK 27
+    onlyIf { false }
+}
 apply plugin: 'com.vanniktech.maven.publish'

nullaway/src/main/java/com/uber/nullaway/dataflow/CoreNullnessStoreInitializer.java

@@ -162,8 +162,14 @@ private NullnessStore lambdaInitialStore(
       Element element = param.getElement();
       Nullness assumed;
       // we treat lambda parameters differently; they "inherit" the nullability of the
-      // corresponding functional interface parameter, unless they are explicitly annotated
-      if (Nullness.hasNullableAnnotation((Symbol) element, config)) {
+      // corresponding functional interface parameter, unless they are explicitly annotated.
+      //
+      // We look for explicit @Nullable annotations on the symbol.  In JDK 27+, sometimes
+      // javac will add a @Nullable annotation to the Type of element based on its own generic
+      // inference.  We don't want to consider that here (it is handled in the type stored in
+      // fiArgumentNullness), so we only look at the annotations directly on element
+      if (Nullness.hasNullableAnnotation(
+          ((Symbol) element).getAnnotationMirrors().stream(), config)) {
         assumed = NULLABLE;
       } else if (!NullabilityUtil.lambdaParamIsImplicitlyTyped(variableTree)) {
         // the parameter has a declared type with no @Nullable annotation