errorprone OptionalOrElseThrowThrows to prevent throwing in orElseThrow

README.md

@@ -163,6 +163,7 @@ Safe Logging can be found at [github.com/palantir/safe-logging](https://github.c
 - `DangerousCompletableFutureUsage`: Disallow CompletableFuture asynchronous operations without an Executor.
 - `NonComparableStreamSort`: Stream.sorted() should only be called on streams of Comparable types.
 - `DangerousStringInternUsage`: Disallow String.intern() invocations in favor of more predictable, scalable alternatives.
+- `OptionalOrElseThrowThrows`: Optional.orElseThrow argument must return an exception, not throw one.
 
 ## 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/OptionalOrElseThrowThrows.java

@@ -0,0 +1,89 @@
+/*
+ * (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.common.collect.Iterables;
+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.method.MethodMatchers;
+import com.sun.source.tree.BlockTree;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.LambdaExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.StatementTree;
+import com.sun.source.tree.ThrowTree;
+import com.sun.source.tree.TreeVisitor;
+import com.sun.source.util.SimpleTreeVisitor;
+import java.util.Optional;
+import java.util.function.Supplier;
+
+@AutoService(BugChecker.class)
+@BugPattern(
+        name = "OptionalOrElseThrowThrows",
+        link = "https://github.com/palantir/gradle-baseline#baseline-error-prone-checks",
+        linkType = BugPattern.LinkType.CUSTOM,
+        severity = BugPattern.SeverityLevel.WARNING,
+        summary = "orElseThrow argument must return an exception, not throw one")
+public class OptionalOrElseThrowThrows extends BugChecker implements BugChecker.MethodInvocationTreeMatcher {
+
+    private static final Matcher<ExpressionTree> OR_ELSE_THROW_METHOD = MethodMatchers.instanceMethod()
+            .onExactClass(Optional.class.getName())
+            .named("orElseThrow")
+            .withParameters(Supplier.class.getName());
+
+    @Override
+    public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+        if (!OR_ELSE_THROW_METHOD.matches(tree, state)) {
+            return Description.NO_MATCH;
+        }
+        ExpressionTree argument = Iterables.getOnlyElement(tree.getArguments());
+        if (!(argument instanceof LambdaExpressionTree)) {
+            return Description.NO_MATCH;
+        }
+        LambdaExpressionTree lambdaArgument = (LambdaExpressionTree) argument;
+        if (!lambdaArgument.getBody().accept(ThrowsPredicateVisitor.INSTANCE, null)) {
+            return Description.NO_MATCH;
+        }
+        return buildDescription(tree)
+                .setMessage("orElseThrow argument must return an exception, not throw one")
+                .build();
+    }
+
+    private static final class ThrowsPredicateVisitor extends SimpleTreeVisitor<Boolean, Void> {
+        static final TreeVisitor<Boolean, Void> INSTANCE = new ThrowsPredicateVisitor();
+
+        private ThrowsPredicateVisitor() {
+            super(false);
+        }
+
+        @Override
+        public Boolean visitThrow(ThrowTree node, Void state) {
+            return true;
+        }
+
+        @Override
+        public Boolean visitBlock(BlockTree node, Void state) {
+            // Only validate the first statement for the most common case to avoid unnecessary complexity
+            StatementTree firstStatement = Iterables.getFirst(node.getStatements(), null);
+            return firstStatement != null && firstStatement.accept(this, state);
+        }
+    }
+}

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

@@ -0,0 +1,84 @@
+/*
+ * (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;
+import java.util.Optional;
+
+public class OptionalOrElseThrowThrowsTest {
+
+    private CompilationTestHelper compilationHelper;
+
+    @Before
+    public void before() {
+        compilationHelper = CompilationTestHelper.newInstance(OptionalOrElseThrowThrows.class, getClass());
+    }
+
+    @Test
+    public void testMethodReference() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import " + Optional.class.getName() + ';',
+                "class Test {",
+                "  public <T> T foo(Optional<T> optional) {",
+                "    return optional.orElseThrow(this::getThrowable);",
+                "  }",
+                "  private RuntimeException getThrowable() {",
+                "    return new RuntimeException();",
+                "  }",
+                "}").doTest();
+    }
+
+    @Test
+    public void testReturns_block() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import " + Optional.class.getName() + ';',
+                "class Test {",
+                "  public <T> T foo(Optional<T> optional) {",
+                "    return optional.orElseThrow(() -> { return new RuntimeException(\"not present\"); });",
+                "  }",
+                "}").doTest();
+    }
+
+    @Test
+    public void testReturns_lambda() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import " + Optional.class.getName() + ';',
+                "class Test {",
+                "  public <T> T foo(Optional<T> optional) {",
+                "    return optional.orElseThrow(() -> new RuntimeException(\"not present\"));",
+                "  }",
+                "}").doTest();
+    }
+
+    @Test
+    public void testThrows_block() {
+        compilationHelper.addSourceLines(
+                "Test.java",
+                "import " + Optional.class.getName() + ';',
+                "class Test {",
+                "  public <T> T foo(Optional<T> optional) {",
+                "    // BUG: Diagnostic contains: orElseThrow argument must return an exception, not throw one",
+                "    return optional.orElseThrow(() -> { throw new RuntimeException(\"not present\"); });",
+                "  }",
+                "}").doTest();
+    }
+}

changelog/@unreleased/pr-759.v2.yml

@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: Implement `OptionalOrElseThrowThrows` to prevent throwing from orElseThrow
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/759