fix #737: Implement DangerousCompletableFutureUsage errorprone check

README.md

@@ -160,6 +160,7 @@ Safe Logging can be found at [github.com/palantir/safe-logging](https://github.c
 - `GradleCacheableTaskAction`: Gradle plugins should not call `Task.doFirst` or `Task.doLast` with a lambda, as that is not cacheable. See [gradle/gradle#5510](https://github.com/gradle/gradle/issues/5510) for more details.
 - `PreferBuiltInConcurrentKeySet`: Discourage relying on Guava's `com.google.common.collect.Sets.newConcurrentHashSet()`, when Java's `java.util.concurrent.ConcurrentHashMap.newKeySet()` serves the same purpose.
 - `JUnit5RuleUsage`: Prevent accidental usage of `org.junit.Rule`/`org.junit.ClassRule` within Junit5 tests
+- `DangerousCompletableFutureUsage`: Disallow CompletableFuture asynchronous operations without an Executor.
 
 ## com.palantir.baseline-checkstyle
 Checkstyle rules can be suppressed on a per-line or per-block basis. (It is good practice to first consider formatting

baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/DangerousCompletableFutureUsage.java

@@ -0,0 +1,103 @@
+/*
+ * (c) Copyright 2019 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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.palantir.baseline.errorprone;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.matchers.Matchers;
+import com.google.errorprone.matchers.method.MethodMatchers;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.tools.javac.code.Symbol;
+import com.sun.tools.javac.code.Type;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.Executor;
+import java.util.function.Supplier;
+import java.util.regex.Pattern;
+
+@AutoService(BugChecker.class)
+@BugPattern(
+        name = "DangerousCompletableFutureUsage",
+        link = "https://github.com/palantir/gradle-baseline#baseline-error-prone-checks",
+        linkType = BugPattern.LinkType.CUSTOM,
+        severity = BugPattern.SeverityLevel.ERROR,
+        summary = "Disallow CompletableFuture asynchronous operations without an Executor.")
+public final class DangerousCompletableFutureUsage
+        extends BugChecker implements BugChecker.MethodInvocationTreeMatcher {
+    private static final long serialVersionUID = 1L;
+
+    private static final String ERROR_MESSAGE = "Should not use CompletableFuture methods without specifying a "
+            + "custom executor service. Doing so has very subtle and potentially severe performance implications, so "
+            + "in you're better off using your own executor service which allows you to provide instrumentation "
+            + "and specify the desired parallelism (i.e. the max number of concurrent tasks that will be submitted).\n"
+            + "By default, CompletableFuture uses the globally shared ForkJoinPool. Fork/join pools implement "
+            + "work-stealing, where any thread might steal a task from a different thread's queue when blocked "
+            + "waiting for a subtask to complete. This might not seem like an issue at first glance, but if you rely"
+            + "on the ForkJoinPool for short tasks extensively throughout your codebase and later on you add one "
+            + "piece of code that uses the pool for long (e.g. I/O) tasks, the other parts of your codebase that"
+            + "you'd expect to have consistent performance might experience performance degradation for no apparent "
+            + "reason.\n"
+            + "If you're absolutely certain that the ForkJoinPool is correct, please pass ForkJoinPool.commonPool()"
+            + "directly, ideally with a comment explaining why it is ideal.";
+
+    private static final Matcher<ExpressionTree> SUPPLY_ASYNC = MethodMatchers.staticMethod()
+            .onClass(CompletableFuture.class.getName())
+            .named("supplyAsync")
+            .withParameters(Supplier.class.getName());
+
+    private static final Matcher<ExpressionTree> RUN_ASYNC = MethodMatchers.staticMethod()
+            .onClass(CompletableFuture.class.getName())
+            .named("runAsync")
+            .withParameters(Runnable.class.getName());
+
+    private static final Matcher<ExpressionTree> STATIC_ASYNC_FACTORY_MATCHERS =
+            Matchers.anyOf(SUPPLY_ASYNC, RUN_ASYNC);
+
+    private static final Matcher<ExpressionTree> COMPLETION_STAGE_ASYNC_INVOCATION = MethodMatchers.instanceMethod()
+            .onDescendantOf(CompletionStage.class.getName())
+            .withNameMatching(Pattern.compile(".*Async"));
+
+    @Override
+    public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+        if (STATIC_ASYNC_FACTORY_MATCHERS.matches(tree, state)
+                || isCompletionStageAsyncMethodWithoutExecutor(tree, state)) {
+            return buildDescription(tree).setMessage(ERROR_MESSAGE).build();
+        }
+        return Description.NO_MATCH;
+    }
+
+    private static boolean isCompletionStageAsyncMethodWithoutExecutor(MethodInvocationTree tree, VisitorState state) {
+        if (COMPLETION_STAGE_ASYNC_INVOCATION.matches(tree, state)) {
+            Symbol.MethodSymbol symbol = ASTHelpers.getSymbol(tree);
+            // Should only happen if there are errors in the AST
+            if (symbol != null) {
+                List<Type> parameterTypes = symbol.type.getParameterTypes();
+                Type lastParameterType = parameterTypes.get(parameterTypes.size() - 1);
+                return !ASTHelpers.isSameType(
+                        lastParameterType, state.getTypeFromString(Executor.class.getName()), state);
+            }
+        }
+        return false;
+    }
+}

baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/DangerousCompletableFutureUsageTest.java

@@ -0,0 +1,146 @@
+/*
+ * (c) Copyright 2019 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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.palantir.baseline.errorprone;
+
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.Before;
+import org.junit.Test;
+
+public final class DangerousCompletableFutureUsageTest {
+    private CompilationTestHelper compilationHelper;
+
+    @Before
+    public void before() {
+        compilationHelper = CompilationTestHelper.newInstance(DangerousCompletableFutureUsage.class, getClass());
+    }
+
+    @Test
+    public void should_fail_without_executor_supplyAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       // BUG: Diagnostic contains: Should not use CompletableFuture methods without specifying",
+                "       CompletableFuture.supplyAsync(() -> 1L);",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_pass_with_executor_supplyAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "import java.util.concurrent.Executors;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       CompletableFuture.supplyAsync(() -> 1L, Executors.newCachedThreadPool());",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_fail_without_executor_runAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       // BUG: Diagnostic contains: Should not use CompletableFuture methods without specifying",
+                "       CompletableFuture.runAsync(() -> {});",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_pass_with_executor_runAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "import java.util.concurrent.Executors;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       CompletableFuture.runAsync(() -> {}, Executors.newCachedThreadPool());",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_fail_without_executor_thenApplyAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       CompletableFuture<Integer> future = CompletableFuture.completedFuture(1);",
+                "       // BUG: Diagnostic contains: Should not use CompletableFuture methods without specifying",
+                "       future.thenApplyAsync(i -> i);",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_pass_with_executor_thenApplyAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "import java.util.concurrent.Executors;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       CompletableFuture.completedFuture(1).thenApplyAsync(i -> i, Executors.newCachedThreadPool());",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_fail_without_executor_applyToEitherAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       CompletableFuture<Integer> futureOne = CompletableFuture.completedFuture(1);",
+                "       CompletableFuture<Integer> futureTwo = CompletableFuture.completedFuture(2);",
+                "       // BUG: Diagnostic contains: Should not use CompletableFuture methods without specifying",
+                "       futureOne.applyToEitherAsync(futureTwo, i -> i);",
+                "   }",
+                "}"
+        ).doTest();
+    }
+
+    @Test
+    public void should_pass_with_executor_applyToEitherAsync() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import java.util.concurrent.CompletableFuture;",
+                "import java.util.concurrent.Executors;",
+                "class Test {",
+                "   public static final void main(String[] args) {",
+                "       CompletableFuture<Integer> futureOne = CompletableFuture.completedFuture(1);",
+                "       CompletableFuture<Integer> futureTwo = CompletableFuture.completedFuture(2);",
+                "       futureOne.applyToEitherAsync(futureTwo, i -> i, Executors.newCachedThreadPool());",
+                "   }",
+                "}"
+        ).doTest();
+    }
+}

changelog/@unreleased/pr-740.v2.yml

@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: Implement DangerousCompletableFutureUsage errorprone check
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/740