Create a check for calls to FileSystems.newFileSystem that will be …

…ambiguous in JDK 13

PiperOrigin-RevId: 494250886

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

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2022 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.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.Description.NO_MATCH;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.matchers.method.MethodMatchers;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.Tree;
+
+/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
+@BugPattern(
+    summary = "Starting in JDK 13, this call is ambiguous with FileSystem.newFileSystem(Path,Map)",
+    severity = WARNING)
+public class NewFileSystem extends BugChecker implements BugChecker.MethodInvocationTreeMatcher {
+
+  private static final Matcher<ExpressionTree> MATCHER =
+      MethodMatchers.staticMethod()
+          .onClass("java.nio.file.FileSystems")
+          .named("newFileSystem")
+          .withParameters("java.nio.file.Path", "java.lang.ClassLoader");
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    if (!MATCHER.matches(tree, state)) {
+      return NO_MATCH;
+    }
+    ExpressionTree expressionTree = tree.getArguments().get(1);
+    if (!expressionTree.getKind().equals(Tree.Kind.NULL_LITERAL)) {
+      return NO_MATCH;
+    }
+    return describeMatch(tree, SuggestedFix.prefixWith(expressionTree, "(ClassLoader) "));
+  }
+}

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

@@ -245,6 +245,7 @@
 import com.google.errorprone.bugpatterns.NarrowingCompoundAssignment;
 import com.google.errorprone.bugpatterns.NegativeCharLiteral;
 import com.google.errorprone.bugpatterns.NestedInstanceOfConditions;
+import com.google.errorprone.bugpatterns.NewFileSystem;
 import com.google.errorprone.bugpatterns.NoAllocationChecker;
 import com.google.errorprone.bugpatterns.NonAtomicVolatileUpdate;
 import com.google.errorprone.bugpatterns.NonCanonicalStaticImport;
@@ -933,6 +934,7 @@ public static ScannerSupplier errorChecks() {
           NarrowingCompoundAssignment.class,
           NegativeCharLiteral.class,
           NestedInstanceOfConditions.class,
+          NewFileSystem.class,
           NonAtomicVolatileUpdate.class,
           NonCanonicalType.class,
           NonOverridingEquals.class,

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

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2022 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 org.junit.Assume.assumeFalse;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.CompilationTestHelper;
+import com.google.errorprone.util.RuntimeVersion;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class NewFileSystemTest {
+
+  private final CompilationTestHelper testHelper =
+      CompilationTestHelper.newInstance(NewFileSystem.class, getClass());
+
+  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
+      BugCheckerRefactoringTestHelper.newInstance(NewFileSystem.class, getClass());
+
+  @Test
+  public void refactoring() {
+    assumeFalse(RuntimeVersion.isAtLeast13());
+    refactoringTestHelper
+        .addInputLines(
+            "Test.java",
+            "import java.nio.file.FileSystems;",
+            "import java.nio.file.Paths;",
+            "import java.io.IOException;",
+            "class Test {",
+            "  void f() throws IOException {",
+            "    FileSystems.newFileSystem(Paths.get(\".\"), null);",
+            "  }",
+            "}")
+        .addOutputLines(
+            "Test.java",
+            "import java.nio.file.FileSystems;",
+            "import java.nio.file.Paths;",
+            "import java.io.IOException;",
+            "class Test {",
+            "  void f() throws IOException {",
+            "    FileSystems.newFileSystem(Paths.get(\".\"), (ClassLoader) null);",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  public void negative() {
+    testHelper
+        .addSourceLines(
+            "Test.java",
+            "import java.nio.file.FileSystems;",
+            "import java.nio.file.Paths;",
+            "import java.io.IOException;",
+            "class Test {",
+            "  void f() throws IOException {",
+            "    FileSystems.newFileSystem(Paths.get(\".\"), (ClassLoader) null);",
+            "  }",
+            "}")
+        .doTest();
+  }
+}

docs/bugpattern/NewFileSystem.md

@@ -0,0 +1,22 @@
+Starting in JDK 13, calls to `FileSystem.newFileSystem(path, null)` are
+ambiguous.
+
+The calls match both:
+
+*   [`FileSystem.newFileSystem(Path, ClassLoader)`](https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/nio/file/FileSystems.html#newFileSystem\(java.nio.file.Path,java.lang.ClassLoader\))
+*   [`FileSystem.newFileSystem(Path, Map<?, ?>)`](https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/nio/file/FileSystems.html#newFileSystem\(java.nio.file.Path,java.util.Map\))
+
+To disambiguate, add a cast to the desired type, to preserve the pre-JDK 13
+behaviour.
+
+That is, prefer this:
+
+```java
+FileSystem.newFileSystem(path, (ClassLoader) null);
+```
+
+Instead of this:
+
+```java
+FileSystem.newFileSystem(path, null);
+```