Add javax.tools.Tool implementation for google-java-format.

core/src/main/java/com/google/googlejavaformat/java/GoogleJavaFormatTool.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2021 Google Inc.
+ *
+ * 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.googlejavaformat.java;
+
+import static com.google.common.collect.Sets.toImmutableEnumSet;
+
+import com.google.auto.service.AutoService;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.util.Arrays;
+import java.util.Set;
+import javax.lang.model.SourceVersion;
+import javax.tools.Tool;
+
+/** Provide a way to be invoked without necessarily starting a new VM. */
+@AutoService(Tool.class)
+public class GoogleJavaFormatTool implements Tool {
+  @Override
+  public String name() {
+    return "google-java-format";
+  }
+
+  @Override
+  public Set<SourceVersion> getSourceVersions() {
+    return Arrays.stream(SourceVersion.values()).collect(toImmutableEnumSet());
+  }
+
+  @Override
+  public int run(InputStream in, OutputStream out, OutputStream err, String... args) {
+    PrintStream outStream = new PrintStream(out);
+    PrintStream errStream = new PrintStream(err);
+    try {
+      return Main.main(in, outStream, errStream, args);
+    } catch (RuntimeException e) {
+      errStream.print(e.getMessage());
+      errStream.flush();
+      return 1; // pass non-zero value back indicating an error has happened
+    }
+  }
+}

core/src/main/java/com/google/googlejavaformat/java/GoogleJavaFormatToolProvider.java

@@ -29,10 +29,11 @@ public String name() {
   @Override
   public int run(PrintWriter out, PrintWriter err, String... args) {
     try {
-      return Main.main(out, err, args);
+      return Main.main(System.in, out, err, args);
     } catch (RuntimeException e) {
       err.print(e.getMessage());
-      return -1; // pass non-zero value back indicating an error has happened
+      err.flush();
+      return 1; // pass non-zero value back indicating an error has happened
     }
   }
 }

core/src/main/java/com/google/googlejavaformat/java/Main.java

@@ -26,6 +26,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStreamWriter;
+import java.io.PrintStream;
 import java.io.PrintWriter;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -66,20 +67,28 @@ public Main(PrintWriter outWriter, PrintWriter errWriter, InputStream inStream)
    *
    * @param args the command-line arguments
    */
-  public static void main(String[] args) {
-    PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out, UTF_8));
-    PrintWriter err = new PrintWriter(new OutputStreamWriter(System.err, UTF_8));
-    int result = main(out, err, args);
+  public static void main(String... args) {
+    int result = main(System.in, System.out, System.err, args);
     System.exit(result);
   }
 
   /**
-   * Package-private main entry point used this CLI program and the java.util.spi.ToolProvider
+   * Package-private main entry point used by the {@link javax.tools.Tool Tool} implementation in
+   * the same package as this Main class.
+   */
+  static int main(InputStream in, PrintStream out, PrintStream err, String... args) {
+    PrintWriter outWriter = new PrintWriter(new OutputStreamWriter(out, UTF_8));
+    PrintWriter errWriter = new PrintWriter(new OutputStreamWriter(err, UTF_8));
+    return main(in, outWriter, errWriter, args);
+  }
+
+  /**
+   * Package-private main entry point used by the {@link java.util.spi.ToolProvider ToolProvider}
    * implementation in the same package as this Main class.
    */
-  static int main(PrintWriter out, PrintWriter err, String... args) {
+  static int main(InputStream in, PrintWriter out, PrintWriter err, String... args) {
     try {
-      Main formatter = new Main(out, err, System.in);
+      Main formatter = new Main(out, err, in);
       return formatter.format(args);
     } catch (UsageException e) {
       err.print(e.getMessage());

core/src/test/java/com/google/googlejavaformat/java/GoogleJavaFormatToolProviderTest.java

@@ -46,7 +46,7 @@ public void testUsageOutputAfterLoadingViaToolName() {
 
     int result = format.run(new PrintWriter(out, true), new PrintWriter(err, true), "--help");
 
-    assertThat(result).isEqualTo(2);
+    assertThat(result).isNotEqualTo(0);
 
     String usage = err.toString();
 

core/src/test/java/com/google/googlejavaformat/java/GoogleJavaFormatToolTest.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2021 Google Inc.
+ *
+ * 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.googlejavaformat.java;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.Truth8.assertThat;
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.util.ServiceLoader;
+import javax.tools.Tool;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link GoogleJavaFormatToolProvider}. */
+@RunWith(JUnit4.class)
+public class GoogleJavaFormatToolTest {
+
+  @Test
+  public void testUsageOutputAfterLoadingViaToolName() {
+    String name = "google-java-format";
+
+    assertThat(
+            ServiceLoader.load(Tool.class).stream()
+                .map(ServiceLoader.Provider::get)
+                .map(Tool::name))
+        .contains(name);
+
+    Tool format =
+        ServiceLoader.load(Tool.class).stream()
+            .filter(provider -> name.equals(provider.get().name()))
+            .findFirst()
+            .get()
+            .get();
+
+    InputStream in = new ByteArrayInputStream(new byte[0]);
+    ByteArrayOutputStream out = new ByteArrayOutputStream();
+    ByteArrayOutputStream err = new ByteArrayOutputStream();
+
+    int result = format.run(in, out, err, "--help");
+
+    assertThat(result).isNotEqualTo(0);
+
+    String usage = new String(err.toByteArray(), UTF_8);
+
+    // Check that doc links are included.
+    assertThat(usage).containsMatch("http.*/google-java-format");
+    assertThat(usage).contains("Usage: google-java-format");
+  }
+}