Internal change.

core/src/test/java/com/google/errorprone/bugpatterns/AsyncCacheLoaderReturnsNullTest.java

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2015 The Error Prone Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns;
+
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link AsyncCacheLoaderReturnsNull}. */
+@RunWith(JUnit4.class)
+public class AsyncCacheLoaderReturnsNullTest {
+  private final CompilationTestHelper compilationHelper =
+      CompilationTestHelper.newInstance(AsyncCacheLoaderReturnsNull.class, getClass());
+
+  @Test
+  public void positiveCase() {
+    compilationHelper
+        .addSourceLines(
+            "AsyncCacheLoaderReturnsNullPositiveCases.java",
+            """
+            package com.google.errorprone.bugpatterns.testdata;
+
+            import static com.google.common.util.concurrent.Futures.immediateFuture;
+
+            import com.google.common.cache.AsyncCacheLoader;
+            import com.google.common.util.concurrent.ListenableFuture;
+
+            /** Positive cases for {@link AsyncCacheLoaderReturnsNull}. */
+            public class AsyncCacheLoaderReturnsNullPositiveCases {
+              static void listenableFutures() {
+                new AsyncCacheLoader<String, Object>() {
+                  @Override
+                  public ListenableFuture<Object> load(String key) {
+                    // BUG: Diagnostic contains:
+                    return null;
+                  }
+                };
+
+                new AsyncCacheLoader<Object, String>() {
+                  @Override
+                  public ListenableFuture<String> load(Object o) {
+                    if (o instanceof String) {
+                      return immediateFuture((String) o);
+                    }
+                    // BUG: Diagnostic contains:
+                    return null;
+                  }
+                };
+              }
+            }
+            """)
+        .doTest();
+  }
+
+  @Test
+  public void negativeCase() {
+    compilationHelper
+        .addSourceLines(
+            "AsyncCacheLoaderReturnsNullNegativeCases.java",
+            """
+            package com.google.errorprone.bugpatterns.testdata;
+
+            import static com.google.common.util.concurrent.Futures.immediateFuture;
+
+            import com.google.common.base.Function;
+            import com.google.common.cache.AsyncCacheLoader;
+            import com.google.common.util.concurrent.ListenableFuture;
+            import java.util.function.Supplier;
+            import org.jspecify.annotations.Nullable;
+
+            /** Negative cases for {@link AsyncCacheLoaderReturnsNull}. */
+            public class AsyncCacheLoaderReturnsNullNegativeCases {
+              static {
+                new AsyncCacheLoader<String, Object>() {
+                  @Override
+                  public ListenableFuture<Object> load(String key) {
+                    return immediateFuture(null);
+                  }
+                };
+
+                new Function<String, Object>() {
+                  @Override
+                  public Object apply(String input) {
+                    return null;
+                  }
+                };
+
+                new AsyncCacheLoader<String, Object>() {
+                  @Override
+                  public ListenableFuture<Object> load(String key) {
+                    return load(key, key);
+                  }
+
+                  public ListenableFuture<Object> load(String input1, String input2) {
+                    return null;
+                  }
+                };
+
+                new MyNonAsyncCacheLoader<String, Object>() {
+                  @Override
+                  public ListenableFuture<Object> load(String key) {
+                    return null;
+                  }
+                };
+
+                new AsyncCacheLoader<String, Object>() {
+                  @Override
+                  public ListenableFuture<Object> load(String key) {
+                    Supplier<String> s =
+                        () -> {
+                          return null;
+                        };
+                    return immediateFuture(s.get());
+                  }
+                };
+              }
+
+              interface MyNonAsyncCacheLoader<K, V> {
+                ListenableFuture<V> load(@Nullable K key);
+              }
+            }
+            """)
+        .doTest();
+  }
+}