[ggj][ast] feat: add EmptyLineStatement

src/main/java/com/google/api/generator/engine/ast/AstNodeVisitor.java

@@ -87,6 +87,8 @@ public interface AstNodeVisitor {
 
   public void visit(CommentStatement commentStatement);
 
+  public void visit(EmptyLineStatement emptyLineStatement);
+
   /** =============================== OTHER =============================== */
   public void visit(MethodDefinition methodDefinition);
 

src/main/java/com/google/api/generator/engine/ast/EmptyLineStatement.java

@@ -0,0 +1,28 @@
+// 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.engine.ast;
+
+public class EmptyLineStatement implements Statement {
+  private EmptyLineStatement() {}
+
+  @Override
+  public void accept(AstNodeVisitor visitor) {
+    visitor.visit(this);
+  }
+
+  public static EmptyLineStatement create() {
+    return new EmptyLineStatement();
+  }
+}

src/main/java/com/google/api/generator/engine/writer/ImportWriterVisitor.java

@@ -25,6 +25,7 @@
 import com.google.api.generator.engine.ast.CastExpr;
 import com.google.api.generator.engine.ast.ClassDefinition;
 import com.google.api.generator.engine.ast.CommentStatement;
+import com.google.api.generator.engine.ast.EmptyLineStatement;
 import com.google.api.generator.engine.ast.EnumRefExpr;
 import com.google.api.generator.engine.ast.Expr;
 import com.google.api.generator.engine.ast.ExprStatement;
@@ -316,23 +317,28 @@ public void visit(SynchronizedStatement synchronizedStatement) {
 
   @Override
   public void visit(CommentStatement commentStatement) {
-    // Do nothing
+    // Nothing to do.
+  }
+
+  @Override
+  public void visit(EmptyLineStatement emptyLineStatement) {
+    // Nothing to do.
   }
 
   /** =============================== COMMENT =============================== */
   @Override
   public void visit(LineComment lineComment) {
-    // Do nothing
+    // Nothing to do.
   }
 
   @Override
   public void visit(BlockComment blockComment) {
-    // Do nothing
+    // Nothing to do.
   }
 
   @Override
   public void visit(JavaDocComment javaDocComment) {
-    // Do nothing
+    // Nothing to do.
   }
 
   /** =============================== OTHER =============================== */

src/main/java/com/google/api/generator/engine/writer/JavaWriterVisitor.java

@@ -25,6 +25,7 @@
 import com.google.api.generator.engine.ast.CastExpr;
 import com.google.api.generator.engine.ast.ClassDefinition;
 import com.google.api.generator.engine.ast.CommentStatement;
+import com.google.api.generator.engine.ast.EmptyLineStatement;
 import com.google.api.generator.engine.ast.EnumRefExpr;
 import com.google.api.generator.engine.ast.Expr;
 import com.google.api.generator.engine.ast.ExprStatement;
@@ -622,6 +623,11 @@ public void visit(CommentStatement commentStatement) {
     commentStatement.comment().accept(this);
   }
 
+  @Override
+  public void visit(EmptyLineStatement emptyLineStatement) {
+    newline();
+  }
+
   /** =============================== COMMENT =============================== */
   public void visit(LineComment lineComment) {
     // Split comments by new line and add `//` to each line.

src/test/java/com/google/api/generator/engine/writer/ImportWriterVisitorTest.java

@@ -14,6 +14,7 @@
 
 package com.google.api.generator.engine.writer;
 
+import static com.google.common.truth.Truth.assertThat;
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertFalse;
 import static junit.framework.Assert.assertTrue;
@@ -25,6 +26,7 @@
 import com.google.api.generator.engine.ast.CastExpr;
 import com.google.api.generator.engine.ast.ClassDefinition;
 import com.google.api.generator.engine.ast.ConcreteReference;
+import com.google.api.generator.engine.ast.EmptyLineStatement;
 import com.google.api.generator.engine.ast.EnumRefExpr;
 import com.google.api.generator.engine.ast.Expr;
 import com.google.api.generator.engine.ast.ExprStatement;
@@ -1020,6 +1022,13 @@ public void writeLogicalOperationExprImports() {
         "import com.google.api.generator.engine.ast.UnaryOperationExpr;\n\n");
   }
 
+  @Test
+  public void writeEmptyLineStatementImports() {
+    EmptyLineStatement statement = EmptyLineStatement.create();
+    statement.accept(writerVisitor);
+    assertThat(writerVisitor.write()).isEmpty();
+  }
+
   private static TypeNode createType(Class clazz) {
     return TypeNode.withReference(ConcreteReference.withClazz(clazz));
   }

src/test/java/com/google/api/generator/engine/writer/JavaWriterVisitorTest.java

@@ -28,6 +28,7 @@
 import com.google.api.generator.engine.ast.ClassDefinition;
 import com.google.api.generator.engine.ast.CommentStatement;
 import com.google.api.generator.engine.ast.ConcreteReference;
+import com.google.api.generator.engine.ast.EmptyLineStatement;
 import com.google.api.generator.engine.ast.EnumRefExpr;
 import com.google.api.generator.engine.ast.Expr;
 import com.google.api.generator.engine.ast.ExprStatement;
@@ -2234,6 +2235,13 @@ public void writeAssignmentOperationExpr_xorAssignment() {
     assertThat(writerVisitor.write()).isEqualTo("h ^= Objects.hashCode(fixedValue)");
   }
 
+  @Test
+  public void writeEmptyLineStatement() {
+    EmptyLineStatement statement = EmptyLineStatement.create();
+    statement.accept(writerVisitor);
+    assertEquals(writerVisitor.write(), "\n");
+  }
+
   private static String createLines(int numLines) {
     return new String(new char[numLines]).replace("\0", "%s");
   }