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

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/main/java/com/google/api/generator/gapic/utils/SampleCodeJavaFormatter.java

@@ -0,0 +1,71 @@
+// 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.utils;
+
+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 RIGHT_BRACE = "}";
+  private static final String LEFT_BRACE = "{";
+  private static final String NEWLINE = "\n";
+
+  private static final String FAKE_CLASS_TITLE =
+      String.format("public class FakeClass %s%s", LEFT_BRACE, NEWLINE);
+  private static final String FAKE_METHOD_TITLE =
+      String.format("void fakeMethod() %s%s", LEFT_BRACE, NEWLINE);
+  private static final String FAKE_METHOD_CLOSE = String.format("%s%s", RIGHT_BRACE, NEWLINE);
+  private static final String FAKE_CLASS_CLOSE = String.format("%s", RIGHT_BRACE);
+
+  /**
+   * This method is used to format sample code by utilizing google-java-format to format the Java
+   * source code.
+   *
+   * @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();
+    buffer.append(FAKE_CLASS_TITLE);
+    buffer.append(FAKE_METHOD_TITLE);
+    buffer.append(sampleCode);
+    buffer.append(FAKE_METHOD_CLOSE);
+    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));
+    }
+    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/test/java/com/google/api/generator/gapic/utils/BUILD.bazel

@@ -4,6 +4,7 @@ package(default_visibility = ["//visibility:public"])
 
 TESTS = [
     "JavaStyleTest",
+    "SampleCodeJavaFormatterTest"
 ]
 
 filegroup(
@@ -16,6 +17,8 @@ filegroup(
     srcs = ["{0}.java".format(test_name)],
     test_class = "com.google.api.generator.gapic.utils.{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/utils",
         "@com_google_truth_truth//jar",
         "@junit_junit//jar",

src/test/java/com/google/api/generator/gapic/utils/SampleCodeJavaFormatterTest.java

@@ -0,0 +1,148 @@
+// 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.utils;
+
+import static junit.framework.TestCase.assertEquals;
+
+import com.google.api.generator.engine.ast.AssignmentExpr;
+import com.google.api.generator.engine.ast.Expr;
+import com.google.api.generator.engine.ast.ExprStatement;
+import com.google.api.generator.engine.ast.MethodInvocationExpr;
+import com.google.api.generator.engine.ast.PrimitiveValue;
+import com.google.api.generator.engine.ast.Statement;
+import com.google.api.generator.engine.ast.TryCatchStatement;
+import com.google.api.generator.engine.ast.TypeNode;
+import com.google.api.generator.engine.ast.Value;
+import com.google.api.generator.engine.ast.ValueExpr;
+import com.google.api.generator.engine.ast.VaporReference;
+import com.google.api.generator.engine.ast.Variable;
+import com.google.api.generator.engine.ast.VariableExpr;
+import com.google.api.generator.engine.writer.JavaWriterVisitor;
+import com.google.api.generator.gapic.utils.SampleCodeJavaFormatter.FormatException;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.Test;
+
+public class SampleCodeJavaFormatterTest {
+
+  @Test
+  public void validFormatSampleCode_tryCatchStatement() {
+    List<Statement> statements = Arrays.asList(createTryCatchSampleCode());
+    String result = SampleCodeJavaFormatter.format(writeStatements(statements));
+    String expected =
+        String.format(createLines(3), "try (boolean condition = false) {\n", "  int x = 3;\n", "}");
+    assertEquals(expected, result);
+  }
+
+  @Test
+  public void validFormatSampleCode_longLineStatement() {
+    TypeNode type =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setPakkage("com.google.pubsub.v1")
+                .setName("SubscriptionAdminSettings")
+                .build());
+    VariableExpr varDclExpr = createVariableDeclExpr("subscriptionAdminSettings", type);
+    VariableExpr varExpr = createVariableExpr("SubscriptionAdminSettings", type);
+    MethodInvocationExpr firstMethodExpr =
+        MethodInvocationExpr.builder()
+            .setMethodName("newBuilder")
+            .setExprReferenceExpr(varExpr)
+            .build();
+    MethodInvocationExpr secondMethodExpr =
+        MethodInvocationExpr.builder()
+            .setMethodName("setEndpoint")
+            .setExprReferenceExpr(firstMethodExpr)
+            .setArguments(Arrays.asList(createVariableExpr("myEndpoint", TypeNode.STRING)))
+            .build();
+    MethodInvocationExpr methodExpr =
+        MethodInvocationExpr.builder()
+            .setMethodName("build")
+            .setExprReferenceExpr(secondMethodExpr)
+            .setReturnType(type)
+            .build();
+    List<Statement> statements =
+        Arrays.asList(
+            ExprStatement.withExpr(
+                AssignmentExpr.builder()
+                    .setVariableExpr(varDclExpr)
+                    .setValueExpr(methodExpr)
+                    .build()));
+    String result = SampleCodeJavaFormatter.format(writeStatements(statements));
+    String expected =
+        String.format(
+            createLines(2),
+            "SubscriptionAdminSettings subscriptionAdminSettings =\n",
+            "    SubscriptionAdminSettings.newBuilder().setEndpoint(myEndpoint).build();");
+    assertEquals(expected, result);
+  }
+
+  @Test(expected = FormatException.class)
+  public void invalidFormatSampleCode_nonStatement() {
+    SampleCodeJavaFormatter.format("abc");
+  }
+
+  /** =============================== HELPERS =============================== */
+  private static String createLines(int numLines) {
+    return new String(new char[numLines]).replace("\0", "%s");
+  }
+
+  private static Statement createTryCatchSampleCode() {
+    TryCatchStatement tryCatch =
+        TryCatchStatement.builder()
+            .setTryResourceExpr(createAssignmentExpr("condition", "false", TypeNode.BOOLEAN))
+            .setTryBody(
+                Arrays.asList(ExprStatement.withExpr(createAssignmentExpr("x", "3", TypeNode.INT))))
+            .setIsSampleCode(true)
+            .build();
+    return tryCatch;
+  }
+
+  private static AssignmentExpr createAssignmentExpr(
+      String variableName, String value, TypeNode type) {
+    VariableExpr variableExpr = createVariableDeclExpr(variableName, type);
+    Value val = PrimitiveValue.builder().setType(type).setValue(value).build();
+    Expr valueExpr = ValueExpr.builder().setValue(val).build();
+    return AssignmentExpr.builder().setVariableExpr(variableExpr).setValueExpr(valueExpr).build();
+  }
+
+  private static VariableExpr createVariableDeclExpr(String variableName, TypeNode type) {
+    return createVariableExpr(variableName, type, true);
+  }
+
+  private static VariableExpr createVariableExpr(String variableName, TypeNode type) {
+    return createVariableExpr(variableName, type, false);
+  }
+
+  private static VariableExpr createVariableExpr(
+      String variableName, TypeNode type, boolean isDecl) {
+    return VariableExpr.builder()
+        .setVariable(createVariable(variableName, type))
+        .setIsDecl(isDecl)
+        .build();
+  }
+
+  private static Variable createVariable(String variableName, TypeNode type) {
+    return Variable.builder().setName(variableName).setType(type).build();
+  }
+
+  private static String writeStatements(List<Statement> statements) {
+    JavaWriterVisitor javaWriterVisitor = new JavaWriterVisitor();
+    for (Statement statement : statements) {
+      statement.accept(javaWriterVisitor);
+    }
+    return javaWriterVisitor.write();
+  }
+}