fix(args): throw when CLI args are not recognized

src/main/java/com/google/cloud/discotoproto3converter/ConverterApp.java

@@ -40,10 +40,23 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 
 public abstract class ConverterApp {
   private final ConverterWriter writer;
 
+  static final Set<String> ALLOWED_ARGUMENTS =
+      new HashSet<>(
+          Arrays.asList(
+              "--discovery_doc_path",
+              "--previous_proto_file_path",
+              "--output_file_path",
+              "--service_ignorelist",
+              "--message_ignorelist",
+              "--relative_link_prefix",
+              "--enums_as_strings",
+              "--output_comments"));
+
   protected ConverterApp(ConverterWriter writer) {
     this.writer = writer;
   }
@@ -108,7 +121,7 @@ public void convert(String[] args) throws IOException {
         parsedArgs.get("--output_comments"));
   }
 
-  private Map<String, String> parseArgs(String[] args) {
+  protected Map<String, String> parseArgs(String[] args) {
     Map<String, String> parsedArgs = new HashMap<>();
 
     // Optional Parameters
@@ -119,7 +132,11 @@ private Map<String, String> parseArgs(String[] args) {
 
     for (String arg : args) {
       String[] argNameVal = arg.split("=");
-      parsedArgs.put(argNameVal[0], argNameVal[1]);
+      String argName = argNameVal[0];
+      if (!ALLOWED_ARGUMENTS.contains(argName)) {
+        throw new IllegalArgumentException(String.format("unrecognized argument \"%s\"", argName));
+      }
+      parsedArgs.put(argName, argNameVal[1]);
     }
 
     return parsedArgs;

src/test/java/com/google/cloud/discotoproto3converter/ConverterAppTest.java

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2024 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
+ *
+ *     https://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.cloud.discotoproto3converter;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import java.util.Map;
+import org.junit.Test;
+
+public class ConverterAppTest {
+
+  @Test
+  public void parseArgsFull() {
+    DiscoToProto3ConverterApp app = new DiscoToProto3ConverterApp();
+    Map<String, String> parsedArgs =
+        app.parseArgs(
+            new String[] {
+              "--discovery_doc_path=alpha",
+              "--previous_proto_file_path=beta",
+              "--output_file_path=gamma",
+              "--service_ignorelist=delta",
+              "--message_ignorelist=epsilon",
+              "--relative_link_prefix=zeta",
+              "--enums_as_strings=eta",
+              "--output_comments=theta"
+            });
+
+    assertEquals("alpha", parsedArgs.get("--discovery_doc_path"));
+    assertEquals("beta", parsedArgs.get("--previous_proto_file_path"));
+    assertEquals("gamma", parsedArgs.get("--output_file_path"));
+    assertEquals("delta", parsedArgs.get("--service_ignorelist"));
+    assertEquals("epsilon", parsedArgs.get("--message_ignorelist"));
+    assertEquals("zeta", parsedArgs.get("--relative_link_prefix"));
+    assertEquals("eta", parsedArgs.get("--enums_as_strings"));
+    assertEquals("theta", parsedArgs.get("--output_comments"));
+  }
+
+  @Test
+  public void parseArgsDefault() {
+    DiscoToProto3ConverterApp app = new DiscoToProto3ConverterApp();
+    Map<String, String> parsedArgs =
+        app.parseArgs(
+            new String[] {
+              "--discovery_doc_path=alpha",
+              "--previous_proto_file_path=beta",
+              "--output_file_path=gamma",
+              "--relative_link_prefix=zeta"
+            });
+
+    assertEquals("alpha", parsedArgs.get("--discovery_doc_path"));
+    assertEquals("beta", parsedArgs.get("--previous_proto_file_path"));
+    assertEquals("gamma", parsedArgs.get("--output_file_path"));
+    assertEquals("", parsedArgs.get("--service_ignorelist"));
+    assertEquals("", parsedArgs.get("--message_ignorelist"));
+    assertEquals("zeta", parsedArgs.get("--relative_link_prefix"));
+    assertEquals("false", parsedArgs.get("--enums_as_strings"));
+    assertEquals("true", parsedArgs.get("--output_comments"));
+  }
+
+  @Test
+  public void parseArgsUnrecognized() {
+    DiscoToProto3ConverterApp app = new DiscoToProto3ConverterApp();
+    assertThrows(
+        java.lang.IllegalArgumentException.class,
+        () ->
+            app.parseArgs(
+                new String[] {
+                  "--discovery_doc_path=alpha",
+                  "--unsupported_arg=omega",
+                  "--previous_proto_file_path=beta",
+                  "--output_file_path=gamma",
+                  "--relative_link_prefix=zeta"
+                }));
+  }
+}