[ggj][infra][2/5] feat: integrate java-diff-util library with dummy test

BUILD.bazel

@@ -15,6 +15,7 @@ JAVA_SRCS = [
 TEST_SRCS = [
     "//src/test/java/com/google/api/generator/engine:engine_files",
     "//src/test/java/com/google/api/generator/gapic:gapic_files",
+    "//src/test/java/com/google/api/generator/test/framework:framework_files",
 ]
 
 # ============= Proto wrappers =================

dependencies.properties

@@ -20,6 +20,7 @@ maven.com_google_code_findbugs_jsr305=com.google.code.findbugs:jsr305:3.0.0
 maven.com_google_auto_value_auto_value=com.google.auto.value:auto-value:1.7.2
 maven.com_google_auto_value_auto_value_annotations=com.google.auto.value:auto-value-annotations:1.7.2
 maven.com_google_protobuf_protobuf_java=com.google.protobuf:protobuf-java:3.12.2
+maven.io_github_java_diff_utils=io.github.java-diff-utils:java-diff-utils:4.0
 maven.javax_annotation_api=javax.annotation:javax.annotation-api:1.3.2
 maven.javax_validation_javax_validation_api=javax.validation:validation-api:2.0.1.Final
 

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

@@ -12,10 +12,12 @@ filegroup(
 [java_test(
     name = test_name,
     srcs = ["{0}.java".format(test_name)],
+    data = ["//src/test/java/com/google/api/generator/gapic/dummy/goldens:goldens_files"],
     test_class = "com.google.api.generator.gapic.dummy.{0}".format(test_name),
     deps = [
         "//src/main/java/com/google/api/generator/engine/ast",
         "//src/main/java/com/google/api/generator/engine/writer",
+        "//src/test/java/com/google/api/generator/test/framework",
         "@junit_junit//jar",
     ],
 ) for test_name in TESTS]

src/test/java/com/google/api/generator/gapic/dummy/FileDiffInfraDummyTest.java

@@ -14,14 +14,15 @@
 
 package com.google.api.generator.gapic.dummy;
 
-import static junit.framework.Assert.assertEquals;
-
 import com.google.api.generator.engine.ast.BlockComment;
 import com.google.api.generator.engine.ast.ClassDefinition;
 import com.google.api.generator.engine.ast.CommentStatement;
 import com.google.api.generator.engine.ast.LineComment;
 import com.google.api.generator.engine.ast.ScopeNode;
 import com.google.api.generator.engine.writer.JavaWriterVisitor;
+import com.google.api.generator.test.framework.Assert;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Arrays;
 import org.junit.Test;
 
@@ -33,6 +34,9 @@ public class FileDiffInfraDummyTest {
   // created.
   //
   // TODO(xiaozhenliu): remove this test class once the file-diff infra is in place and well-tested.
+  private static final String GOLDENFILES_DIRECTORY =
+      "src/test/java/com/google/api/generator/gapic/dummy/goldens/";
+
   @Test
   public void simpleClass() {
     ClassDefinition classDef =
@@ -47,7 +51,9 @@ public void simpleClass() {
             .build();
     JavaWriterVisitor visitor = new JavaWriterVisitor();
     classDef.accept(visitor);
-    assertEquals(visitor.write(), EXPECTED_CLASS_STRING_SIMPLE);
+    Path goldenFilePath =
+        Paths.get(GOLDENFILES_DIRECTORY, "FileDiffInfraDummyTestSimpleClass.golden");
+    Assert.assertCodeEquals(goldenFilePath, visitor.write());
   }
 
   @Test
@@ -63,7 +69,18 @@ public void classWithHeader() {
             .build();
     JavaWriterVisitor visitor = new JavaWriterVisitor();
     classDef.accept(visitor);
-    assertEquals(visitor.write(), EXPECTED_CLASS_STRING_WITH_HEADER);
+    Path goldenFilePath =
+        Paths.get(GOLDENFILES_DIRECTORY, "FileDiffInfraDummyTestClassWithHeader.golden");
+    Assert.assertCodeEquals(goldenFilePath, visitor.write());
+  }
+
+  // Add a simple test for two strings comparison.
+  @Test
+  public void simpleLineComment() {
+    JavaWriterVisitor visitor = new JavaWriterVisitor();
+    LineComment lineComment = LineComment.withComment("test strings comparison.");
+    lineComment.accept(visitor);
+    Assert.assertCodeEquals("// test strings comparison.", visitor.write());
   }
 
   private static final String APACHE_LICENSE_STRING =
@@ -77,28 +94,4 @@ public void classWithHeader() {
           + "WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n"
           + "See the License for the specific language governing permissions and\n"
           + "limitations under the License.";
-
-  private static final String EXPECTED_CLASS_STRING_SIMPLE =
-      "package com.google.showcase.v1beta1.stub;\n\n"
-          + "// This is a test class for file-diff infra\n"
-          + "public class EchoStubSettings {}\n";
-
-  private static final String EXPECTED_CLASS_STRING_WITH_HEADER =
-      "/*\n"
-          + " * Copyright 2020 Google LLC\n"
-          + " *\n"
-          + " * Licensed under the Apache License, Version 2.0 (the \"License\");\n"
-          + " * you may not use this file except in compliance with the License.\n"
-          + " * You may obtain a copy of the License at\n"
-          + " *\n"
-          + " *      https://www.apache.org/licenses/LICENSE-2.0\n"
-          + " *\n"
-          + " * Unless required by applicable law or agreed to in writing, software\n"
-          + " * distributed under the License is distributed on an \"AS IS\" BASIS,\n"
-          + " * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n"
-          + " * See the License for the specific language governing permissions and\n"
-          + " * limitations under the License.\n"
-          + " */\n\n"
-          + "package com.google.showcase.v1beta1.stub;\n\n"
-          + "public class EchoStubSettings {}\n";
 }

src/test/java/com/google/api/generator/test/framework/Assert.java

@@ -0,0 +1,44 @@
+// 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.test.framework;
+
+import java.nio.file.Path;
+import java.util.List;
+import junit.framework.AssertionFailedError;
+
+public class Assert {
+  /**
+   * Assert that the generated code is identical with the content in corresponding golden file. The
+   * differences will be emitted to the test-logs if any.
+   *
+   * @param goldenPath the path of the golden file.
+   * @param codegen the generated source code.
+   */
+  public static void assertCodeEquals(Path goldenPath, String codegen) {
+    List<String> diffList = Differ.diff(goldenPath, codegen);
+    if (!diffList.isEmpty()) {
+      throw new AssertionFailedError("Differences found: \n" + String.join("\n", diffList));
+    }
+  }
+
+  // Assert that two strings are identical, else throw AssertionFailedError and emit the
+  // differences to the test-logs.
+  public static void assertCodeEquals(String expected, String codegen) {
+    List<String> diffList = Differ.diff(expected, codegen);
+    if (!diffList.isEmpty()) {
+      throw new AssertionFailedError("Differences found: \n" + String.join("\n", diffList));
+    }
+  }
+}

src/test/java/com/google/api/generator/test/framework/BUILD.bazel

@@ -0,0 +1,17 @@
+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "framework_files",
+    srcs = glob(["*.java"]),
+)
+
+java_library(
+    name = "framework",
+    srcs = [
+        ":framework_files",
+    ],
+    deps = [
+        "@io_github_java_diff_utils//jar",
+        "@junit_junit//jar",
+    ],
+)

src/test/java/com/google/api/generator/test/framework/Differ.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.test.framework;
+
+import com.github.difflib.DiffUtils;
+import com.github.difflib.UnifiedDiffUtils;
+import com.github.difflib.algorithm.DiffException;
+import com.github.difflib.patch.Patch;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.List;
+
+public class Differ {
+  private static final String LINE_SPLITTER = "\\r?\\n";
+
+  public static List<String> diff(Path goldenFilePath, String codegen) {
+    List<String> revised = Arrays.asList(codegen.split(LINE_SPLITTER));
+    List<String> original = null;
+    try {
+      original = Files.readAllLines(goldenFilePath);
+    } catch (IOException e) {
+      throw new GoldenFileReadException(
+          String.format("Error occurs when reading golden file %s", goldenFilePath));
+    }
+    return diffTwoStringLists(original, revised);
+  }
+
+  public static List<String> diff(String expectedStr, String actualStr) {
+    List<String> revised = Arrays.asList(actualStr.split(LINE_SPLITTER));
+    List<String> original = Arrays.asList(expectedStr.split(LINE_SPLITTER));
+    return diffTwoStringLists(original, revised);
+  }
+
+  private static List<String> diffTwoStringLists(List<String> original, List<String> revised) {
+    Patch<String> diff = null;
+    try {
+      diff = DiffUtils.diff(original, revised);
+    } catch (DiffException e) {
+      throw new ComputeDiffException("Could not compute the differences.");
+    }
+    List<String> unifiedDiff =
+        UnifiedDiffUtils.generateUnifiedDiff("golden", "codegen", original, diff, 2);
+    return unifiedDiff;
+  }
+
+  private static class GoldenFileReadException extends RuntimeException {
+    public GoldenFileReadException(String errorMessage) {
+      super(errorMessage);
+    }
+  }
+
+  private static class ComputeDiffException extends RuntimeException {
+    public ComputeDiffException(String errorMessage) {
+      super(errorMessage);
+    }
+  }
+}