Bug pattern for Futures.transformAsync and other similar methods.

Generated CL for reference: unknown commit. This includes 2,596 findings in 1,418 files.

TAP train of the generated CL: []

PiperOrigin-RevId: 681147365

core/src/main/java/com/google/errorprone/bugpatterns/FutureTransformAsync.java

@@ -0,0 +1,191 @@
+/*
+ * Copyright 2024 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 static com.google.common.collect.Sets.union;
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.Description.NO_MATCH;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod;
+import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+import static com.google.errorprone.util.ASTHelpers.enclosingClass;
+import static com.google.errorprone.util.ASTHelpers.getSymbol;
+import static com.google.errorprone.util.ASTHelpers.getThrownExceptions;
+import static com.google.errorprone.util.ASTHelpers.isCheckedExceptionType;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.util.concurrent.ClosingFuture;
+import com.google.common.util.concurrent.FluentFuture;
+import com.google.common.util.concurrent.Futures;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.fixes.SuggestedFixes;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.BlockTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.LambdaExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.ReturnTree;
+import com.sun.source.util.TreePath;
+import com.sun.source.util.TreePathScanner;
+import com.sun.tools.javac.code.Symbol;
+import java.util.HashSet;
+import java.util.Optional;
+
+/** See summary for details. */
+@BugPattern(
+    summary = "Use transform instead of transformAsync when all returns are an immediate future.",
+    severity = WARNING)
+public final class FutureTransformAsync extends BugChecker implements MethodInvocationTreeMatcher {
+
+  private static final ImmutableSet<String> CLASSES_WITH_STATIC_METHOD =
+      ImmutableSet.of(Futures.class.getName());
+
+  private static final ImmutableSet<String> CLASSES_WITH_INSTANCE_METHOD =
+      ImmutableSet.of(ClosingFuture.class.getName(), FluentFuture.class.getName());
+
+  private static final Matcher<ExpressionTree> TRANSFORM_ASYNC_MATCHER =
+      anyOf(
+          staticMethod().onClassAny(CLASSES_WITH_STATIC_METHOD).named("transformAsync"),
+          instanceMethod().onExactClassAny(CLASSES_WITH_INSTANCE_METHOD).named("transformAsync"));
+
+  private static final Matcher<ExpressionTree> IMMEDIATE_FUTURE =
+      staticMethod()
+          .onClassAny(union(CLASSES_WITH_STATIC_METHOD, CLASSES_WITH_INSTANCE_METHOD))
+          .named("immediateFuture");
+
+  private static final Matcher<ExpressionTree> IMMEDIATE_VOID_FUTURE =
+      staticMethod()
+          .onClassAny(union(CLASSES_WITH_STATIC_METHOD, CLASSES_WITH_INSTANCE_METHOD))
+          .named("immediateVoidFuture");
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    if (!TRANSFORM_ASYNC_MATCHER.matches(tree, state)) {
+      return NO_MATCH;
+    }
+
+    // Find the lambda expression. The transformAsync() methods might have different number of
+    // arguments, but they all have a single lambda. Also discard the lambdas that throw checked
+    // exceptions, since they cannot be supported by transform().
+    Optional<LambdaExpressionTree> lambda =
+        tree.getArguments().stream()
+            .filter(LambdaExpressionTree.class::isInstance)
+            .map(arg -> (LambdaExpressionTree) arg)
+            .filter(lambdaTree -> !throwsCheckedException(lambdaTree, state))
+            .findFirst();
+
+    return lambda.map(lambdaTree -> handleTransformAsync(tree, lambdaTree, state)).orElse(NO_MATCH);
+  }
+
+  private Description handleTransformAsync(
+      MethodInvocationTree tree, LambdaExpressionTree lambda, VisitorState state) {
+    HashSet<ExpressionTree> returnExpressions = new HashSet<>();
+    if (lambda.getBody() instanceof ExpressionTree) {
+      returnExpressions.add((ExpressionTree) lambda.getBody());
+    } else if (lambda.getBody() instanceof BlockTree) {
+      new TreePathScanner<Void, Void>() {
+        @Override
+        public Void visitLambdaExpression(LambdaExpressionTree node, Void unused) {
+          // don't descend into lambdas (to handle nested lambdas)
+          return null;
+        }
+
+        @Override
+        public Void visitClass(ClassTree node, Void unused) {
+          // don't descend into classes (to handle nested classes)
+          return null;
+        }
+
+        @Override
+        public Void visitReturn(ReturnTree tree, Void unused) {
+          returnExpressions.add(tree.getExpression());
+          // Don't descend deeper into returns, since we already checked the body of this return.
+          return null;
+        }
+      }.scan(TreePath.getPath(state.getPath().getCompilationUnit(), lambda.getBody()), null);
+    } else {
+      return NO_MATCH;
+    }
+
+    boolean areAllImmediateFutures =
+        returnExpressions.stream()
+            .allMatch(
+                expression ->
+                    expression instanceof MethodInvocationTree
+                        && (IMMEDIATE_FUTURE.matches(expression, state)
+                            || IMMEDIATE_VOID_FUTURE.matches(expression, state)));
+
+    if (areAllImmediateFutures) {
+      SuggestedFix.Builder fix = SuggestedFix.builder();
+      suggestFixTransformAsyncToTransform(tree, state, fix);
+      for (ExpressionTree expression : returnExpressions) {
+        suggestFixRemoveImmediateFuture((MethodInvocationTree) expression, state, fix);
+      }
+      state.reportMatch(describeMatch(tree, fix.build()));
+    }
+
+    return NO_MATCH;
+  }
+
+  /** Returns true if the lambda throws a checked exception. */
+  private static boolean throwsCheckedException(LambdaExpressionTree lambda, VisitorState state) {
+    return getThrownExceptions(lambda.getBody(), state).stream()
+        .anyMatch(type -> isCheckedExceptionType(type, state));
+  }
+
+  /**
+   * Suggests fix to replace transformAsync with transform.
+   *
+   * <p>If the transformAsync is imported as a static method, it takes care of adding the equivalent
+   * import static for transform.
+   */
+  private static void suggestFixTransformAsyncToTransform(
+      MethodInvocationTree tree, VisitorState state, SuggestedFix.Builder fix) {
+    ExpressionTree methodSelect = tree.getMethodSelect();
+    if (state.getSourceForNode(methodSelect).equals("transformAsync")) {
+      Symbol symbol = getSymbol(methodSelect);
+      String className = enclosingClass(symbol).getQualifiedName().toString();
+      fix.addStaticImport(className + "." + "transform");
+    }
+    fix.merge(SuggestedFixes.renameMethodInvocation(tree, "transform", state));
+  }
+
+  /** Suggests fix to remove the immediateFuture or immediateVoidFuture call. */
+  private static void suggestFixRemoveImmediateFuture(
+      MethodInvocationTree tree, VisitorState state, SuggestedFix.Builder fix) {
+    String typeArgument = "";
+    String argument = "";
+    if (IMMEDIATE_FUTURE.matches(tree, state)) {
+      var typeArguments = tree.getTypeArguments();
+      if (typeArguments.size() == 1) {
+        typeArgument = state.getSourceForNode(typeArguments.get(0));
+      }
+      argument = state.getSourceForNode(tree.getArguments().get(0));
+    } else if (IMMEDIATE_VOID_FUTURE.matches(tree, state)) {
+      typeArgument = "Void";
+      argument = "null";
+    }
+    String fixString =
+        typeArgument.isEmpty() ? argument : String.format("(%s) %s", typeArgument, argument);
+    fix.replace(tree, fixString);
+  }
+}

core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java

@@ -156,6 +156,7 @@
 import com.google.errorprone.bugpatterns.FunctionalInterfaceClash;
 import com.google.errorprone.bugpatterns.FunctionalInterfaceMethodChanged;
 import com.google.errorprone.bugpatterns.FutureReturnValueIgnored;
+import com.google.errorprone.bugpatterns.FutureTransformAsync;
 import com.google.errorprone.bugpatterns.FuturesGetCheckedIllegalExceptionType;
 import com.google.errorprone.bugpatterns.FuzzyEqualsShouldNotBeUsedInEqualsMethod;
 import com.google.errorprone.bugpatterns.GetClassOnAnnotation;
@@ -929,6 +930,7 @@ public static ScannerSupplier warningChecks() {
           FragmentInjection.class,
           FragmentNotInstantiable.class,
           FutureReturnValueIgnored.class,
+          FutureTransformAsync.class,
           GetClassOnEnum.class,
           GuiceNestedCombine.class,
           HidingField.class,