[composer][SampleCode]Utils function formatter for Sample Code

src/main/java/com/google/api/generator/gapic/composer/samplecode/BUILD.bazel

@@ -0,0 +1,18 @@
+load("@rules_java//java:defs.bzl", "java_library")
+
+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "samplecode_files",
+    srcs = glob(["*.java"]),
+)
+
+java_library(
+    name = "samplecode",
+    srcs = [
+        ":samplecode_files",
+    ],
+    deps = [
+        "@google_java_format_all_deps//jar",
+    ],
+)

src/main/java/com/google/api/generator/gapic/composer/samplecode/SampleCodeJavaFormatter.java

@@ -0,0 +1,67 @@
+// Copyright 2020 Google LLC
+//
+// 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.api.generator.gapic.composer.samplecode;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.googlejavaformat.java.Formatter;
+import com.google.googlejavaformat.java.FormatterException;
+
+public final class SampleCodeJavaFormatter {
+
+  private SampleCodeJavaFormatter() {}
+
+  private static final Formatter FORMATTER = new Formatter();
+
+  private static final String FAKE_CLASS_TITLE = "public class FakeClass { void fakeMethod() {";
+  private static final String FAKE_CLASS_CLOSE = "}}";
+
+  /**
+   * This method is used to format sample code string.
+   *
+   * @param sampleCode A string is composed by statements.
+   * @return String Formatted sample code string based on google java style.
+   */
+  public static String format(String sampleCode) {
+    final StringBuffer buffer = new StringBuffer();
+    // Wrap the sample code inside a class for composing a valid Java source code.
+    // Because we utilized google-java-format to reformat the codes.
+    buffer.append(FAKE_CLASS_TITLE);
+    buffer.append(sampleCode);
+    buffer.append(FAKE_CLASS_CLOSE);
+
+    String formattedString = null;
+    try {
+      formattedString = FORMATTER.formatSource(buffer.toString());
+    } catch (FormatterException e) {
+      throw new FormatException(
+          String.format("The sample code should be string where is composed by statements; %s", e));
+    }
+    // Extract formatted sample code by
+    // 1. Removing the first and last two lines.
+    // 2. Delete the first 4 space for each line.
+    // 3. Trim the last new empty line.
+    return formattedString
+        .replaceAll("^([^\n]*\n){2}|([^\n]*\n){2}$", "")
+        .replaceAll("(?m)^ {4}", "")
+        .trim();
+  }
+
+  @VisibleForTesting
+  protected static class FormatException extends RuntimeException {
+    public FormatException(String errorMessage) {
+      super(errorMessage);
+    }
+  }
+}

src/main/java/com/google/api/generator/gapic/utils/BUILD.bazel

@@ -15,5 +15,6 @@ java_library(
     deps = [
         "//src/main/java/com/google/api/generator/engine/ast",
         "@com_google_guava_guava//jar",
+        "@google_java_format_all_deps//jar",
     ],
 )

src/test/java/com/google/api/generator/gapic/composer/samplecode/BUILD.bazel

@@ -0,0 +1,25 @@
+load("@rules_java//java:defs.bzl", "java_test")
+
+package(default_visibility = ["//visibility:public"])
+
+TESTS = [
+    "SampleCodeJavaFormatterTest",
+]
+
+filegroup(
+    name = "samplecode_files",
+    srcs = ["{0}.java".format(f) for f in TESTS],
+)
+
+[java_test(
+    name = test_name,
+    srcs = ["{0}.java".format(test_name)],
+    test_class = "com.google.api.generator.gapic.composer.samplecode.{0}".format(test_name),
+    deps = [
+        "//src/main/java/com/google/api/generator/engine/ast",
+        "//src/main/java/com/google/api/generator/engine/writer",
+        "//src/main/java/com/google/api/generator/gapic/composer/samplecode",
+        "@com_google_truth_truth//jar",
+        "@junit_junit//jar",
+    ],
+) for test_name in TESTS]

src/test/java/com/google/api/generator/gapic/composer/samplecode/SampleCodeJavaFormatterTest.java

@@ -0,0 +1,86 @@
+// Copyright 2020 Google LLC
+//
+// 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.api.generator.gapic.composer.samplecode;
+
+import static junit.framework.TestCase.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import com.google.api.generator.gapic.composer.samplecode.SampleCodeJavaFormatter;
+import com.google.api.generator.gapic.composer.samplecode.SampleCodeJavaFormatter.FormatException;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.Test;
+
+public class SampleCodeJavaFormatterTest {
+
+  @Test
+  public void validFormatSampleCode_tryCatchStatement() {
+    String samplecode = String.format(createLines(3),
+        "try(boolean condition = false){",
+        "int x = 3;",
+        "}");
+    String result = SampleCodeJavaFormatter.format(samplecode);
+    String expected =
+        String.format(createLines(3), "try (boolean condition = false) {\n", "  int x = 3;\n", "}");
+    assertEquals(expected, result);
+  }
+
+  @Test
+  public void validFormatSampleCode_longLineStatement() {
+    String sampleCode =
+        "SubscriptionAdminSettings subscriptionAdminSettings = "
+            + "SubscriptionAdminSettings.newBuilder().setEndpoint(myEndpoint).build();";
+    String result = SampleCodeJavaFormatter.format(sampleCode);
+    String expected =
+        String.format(
+            createLines(2),
+            "SubscriptionAdminSettings subscriptionAdminSettings =\n",
+            "    SubscriptionAdminSettings.newBuilder().setEndpoint(myEndpoint).build();");
+    assertEquals(expected, result);
+  }
+
+  @Test
+  public void validFormatSampleCode_longChainMethod() {
+    String sampleCode = "echoSettingsBuilder.echoSettings().setRetrySettings(echoSettingsBuilder.echoSettings().getRetrySettings().toBuilder().setTotalTimeout(Duration.ofSeconds(30)).build());";
+    String result = SampleCodeJavaFormatter.format(sampleCode);
+    String expected =
+        String.format(
+            createLines(9),
+            "echoSettingsBuilder\n",
+            "    .echoSettings()\n",
+            "    .setRetrySettings(\n",
+            "        echoSettingsBuilder\n",
+            "            .echoSettings()\n",
+            "            .getRetrySettings()\n",
+            "            .toBuilder()\n",
+            "            .setTotalTimeout(Duration.ofSeconds(30))\n",
+            "            .build());");
+    assertEquals(expected, result);
+  }
+
+  @Test
+  public void invalidFormatSampleCode_nonStatement() {
+    assertThrows(
+        FormatException.class,
+        () -> {
+          SampleCodeJavaFormatter.format("abc");
+        });
+  }
+
+  /** =============================== HELPERS =============================== */
+  private static String createLines(int numLines) {
+    return new String(new char[numLines]).replace("\0", "%s");
+  }
+}