feat: add ThisObjectValue

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

@@ -0,0 +1,54 @@
+// 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;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Preconditions;
+
+@AutoValue
+public abstract class ThisObjectValue implements ObjectValue {
+  private static final String THIS_VALUE = "this";
+
+  @Override
+  public abstract TypeNode type();
+
+  @Override
+  public String value() {
+    return THIS_VALUE;
+  }
+
+  public static ThisObjectValue withType(TypeNode type) {
+    return builder().setType(type).build();
+  }
+
+  private static Builder builder() {
+    return new AutoValue_ThisObjectValue.Builder();
+  }
+
+  @AutoValue.Builder
+  abstract static class Builder {
+    abstract Builder setType(TypeNode type);
+
+    abstract ThisObjectValue autoBuild();
+
+    private ThisObjectValue build() {
+      ThisObjectValue thisObjectValue = autoBuild();
+      Preconditions.checkState(
+          TypeNode.isReferenceType(thisObjectValue.type()),
+          "The \"this\" object can only refer to object types");
+      return thisObjectValue;
+    }
+  }
+}

src/test/java/com/google/api/generator/engine/ast/BUILD.bazel

@@ -25,6 +25,7 @@ TESTS = [
     "VariableTest",
     "VaporReferenceTest",
     "MethodInvocationExprTest",
+    "ThisObjectValueTest",
 ]
 
 filegroup(

src/test/java/com/google/api/generator/engine/ast/ThisObjectValueTest.java

@@ -0,0 +1,51 @@
+// 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;
+
+import static org.junit.Assert.assertThrows;
+
+import org.junit.Test;
+
+public class ThisObjectValueTest {
+  @Test
+  public void validThisObjectValue_basic() {
+    VaporReference ref =
+        VaporReference.builder()
+            .setName("Student")
+            .setPakkage("com.google.example.examples.v1")
+            .build();
+    TypeNode typeNode = TypeNode.withReference(ref);
+    ThisObjectValue.withType(typeNode);
+    // No exception thrown, we're good.
+  }
+
+  @Test
+  public void invalidThisObjectValue_nonReferenceType() {
+    assertThrows(
+        IllegalStateException.class,
+        () -> {
+          ThisObjectValue.withType(TypeNode.DOUBLE);
+        });
+  }
+
+  @Test
+  public void invalidThisObjectValue_nullType() {
+    assertThrows(
+        IllegalStateException.class,
+        () -> {
+          ThisObjectValue.withType(TypeNode.NULL);
+        });
+  }
+}

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

@@ -44,6 +44,7 @@
 import com.google.api.generator.engine.ast.Statement;
 import com.google.api.generator.engine.ast.StringObjectValue;
 import com.google.api.generator.engine.ast.TernaryExpr;
+import com.google.api.generator.engine.ast.ThisObjectValue;
 import com.google.api.generator.engine.ast.ThrowExpr;
 import com.google.api.generator.engine.ast.TryCatchStatement;
 import com.google.api.generator.engine.ast.TypeNode;
@@ -1654,6 +1655,54 @@ public void writeClassDefinition_statementsAndMethods() {
             "}\n"));
   }
 
+  @Test
+  public void writeThisObjectValue_methodReturn() {
+    VaporReference ref =
+        VaporReference.builder().setName("Student").setPakkage("com.google.example.v1").build();
+    TypeNode classType = TypeNode.withReference(ref);
+    MethodDefinition methodDefinition =
+        MethodDefinition.builder()
+            .setName("apply")
+            .setScope(ScopeNode.PUBLIC)
+            .setReturnType(TypeNode.withReference(ref))
+            .setReturnExpr(
+                ValueExpr.builder().setValue(ThisObjectValue.withType(classType)).build())
+            .build();
+    methodDefinition.accept(writerVisitor);
+    assertEquals(
+        writerVisitor.write(),
+        String.format("public Student apply() {\n" + "return this;\n" + "}\n"));
+  }
+
+  @Test
+  public void writeThisObjectValue_accessFieldAndInvokeMethod() {
+    VaporReference ref =
+        VaporReference.builder().setName("Student").setPakkage("com.google.example.v1").build();
+    TypeNode classType = TypeNode.withReference(ref);
+    ThisObjectValue thisObjectValue = ThisObjectValue.withType(classType);
+    ValueExpr thisValueExpr = ValueExpr.withValue(thisObjectValue);
+    VariableExpr varExpr =
+        VariableExpr.builder()
+            .setVariable(Variable.builder().setName("id").setType(TypeNode.STRING).build())
+            .build();
+    Variable subVariable = Variable.builder().setName("name").setType(TypeNode.STRING).build();
+    VariableExpr thisVariableExpr =
+        VariableExpr.builder().setVariable(subVariable).setExprReferenceExpr(thisValueExpr).build();
+
+    MethodInvocationExpr methodExpr =
+        MethodInvocationExpr.builder()
+            .setMethodName("getName")
+            .setExprReferenceExpr(ValueExpr.withValue(thisObjectValue))
+            .setArguments(Arrays.asList(varExpr))
+            .setReturnType(TypeNode.STRING)
+            .build();
+    AssignmentExpr assignmentExpr =
+        AssignmentExpr.builder().setVariableExpr(thisVariableExpr).setValueExpr(methodExpr).build();
+
+    assignmentExpr.accept(writerVisitor);
+    assertThat(writerVisitor.write()).isEqualTo("this.name = this.getName(id)");
+  }
+
   private static String createLines(int numLines) {
     return new String(new char[numLines]).replace("\0", "%s");
   }