Add basic test coverage for sysystemfeatures-gen args

Test the following scenarios:
 * An invalid feature version is provided
 * An "android"-prefixed raw feature name is provided

In the case of the latter, any "android"-namespaced feature
must come by way of an existing PackagerManager.FEATURE_ definition.

Bug: 376463304
Test: atest systemfeatures-gen-tests
Flag: build.RELEASE_USE_SYSTEM_FEATURE_BUILD_FLAGS
Change-Id: If74899b5ebeeee7db0e9b2c8162076f8edd4381f

3 files changed, 112 insertions, 4 deletions

diff --git a/tools/systemfeatures/Android.bp b/tools/systemfeatures/Android.bp
index 590f7190881a..e6d0a3d4149f 100644
--- a/tools/systemfeatures/Android.bp
+++ b/tools/systemfeatures/Android.bp
@@ -58,6 +58,7 @@ java_test_host {
         "junit",
         "objenesis",
         "mockito",
+        "systemfeatures-gen-lib",
         "truth",
     ],
 }
diff --git a/tools/systemfeatures/src/com/android/systemfeatures/SystemFeaturesGenerator.kt b/tools/systemfeatures/src/com/android/systemfeatures/SystemFeaturesGenerator.kt
index 196b5e7c02ab..1abe77fd3ceb 100644
--- a/tools/systemfeatures/src/com/android/systemfeatures/SystemFeaturesGenerator.kt
+++ b/tools/systemfeatures/src/com/android/systemfeatures/SystemFeaturesGenerator.kt
@@ -71,7 +71,7 @@ object SystemFeaturesGenerator {
         println("Usage: SystemFeaturesGenerator <outputClassName> [options]")
         println(" Options:")
         println("  --readonly=true|false    Whether to encode features as build-time constants")
-        println("  --feature=\$NAME:\$VER   A feature+version pair, where \$VER can be:")
+        println("  --feature=\$NAME:\$VER     A feature+version pair, where \$VER can be:")
         println("                             * blank/empty == undefined (variable API)")
         println("                             * valid int   == enabled   (constant API)")
         println("                             * UNAVAILABLE == disabled  (constant API)")
@@ -89,6 +89,17 @@ object SystemFeaturesGenerator {
     /** Main entrypoint for build-time system feature codegen. */
     @JvmStatic
     fun main(args: Array<String>) {
+        generate(args, System.out)
+    }
+
+    /**
+     * Simple API entrypoint for build-time system feature codegen.
+     *
+     * Note: Typically this would be implemented in terms of a proper Builder-type input argument,
+     * but it's primarily used for testing as opposed to direct production usage.
+     */
+    @JvmStatic
+    fun generate(args: Array<String>, output: Appendable) {
         if (args.size < 1) {
             usage()
             return
@@ -155,7 +166,7 @@ object SystemFeaturesGenerator {
             .addFileComment("This file is auto-generated. DO NOT MODIFY.\n")
             .addFileComment("Args: ${args.joinToString(" \\\n           ")}")
             .build()
-            .writeTo(System.out)
+            .writeTo(output)
     }
 
     /*
@@ -171,12 +182,27 @@ object SystemFeaturesGenerator {
         return when (featureArgs.getOrNull(1)) {
             null, "" -> FeatureInfo(name, null, readonly = false)
             "UNAVAILABLE" -> FeatureInfo(name, null, readonly = true)
-            else -> FeatureInfo(name, featureArgs[1].toIntOrNull(), readonly = true)
+            else -> {
+                val featureVersion =
+                    featureArgs[1].toIntOrNull()
+                        ?: throw IllegalArgumentException(
+                            "Invalid feature version input for $name: ${featureArgs[1]}"
+                        )
+                FeatureInfo(name, featureArgs[1].toInt(), readonly = true)
+            }
         }
     }
 
     private fun parseFeatureName(name: String): String =
-        if (name.startsWith("FEATURE_")) name else "FEATURE_$name"
+        when {
+            name.startsWith("android") ->
+                throw IllegalArgumentException(
+                    "Invalid feature name input: \"android\"-namespaced features must be " +
+                    "provided as PackageManager.FEATURE_* suffixes, not raw feature strings."
+                )
+            name.startsWith("FEATURE_") -> name
+            else -> "FEATURE_$name"
+        }
 
     /*
      * Adds per-feature query methods to the class with the form:
diff --git a/tools/systemfeatures/tests/src/SystemFeaturesGeneratorApiTest.java b/tools/systemfeatures/tests/src/SystemFeaturesGeneratorApiTest.java
new file mode 100644
index 000000000000..f8c585d60ef7
--- /dev/null
+++ b/tools/systemfeatures/tests/src/SystemFeaturesGeneratorApiTest.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * 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.android.systemfeatures;
+
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnit;
+import org.mockito.junit.MockitoRule;
+
+import java.io.IOException;
+
+// Note: This is a very simple argument test to validate certain behaviors for
+// invalid arguments. Correctness and validity is largely exercised by
+// SystemFeaturesGeneratorTest.
+@RunWith(JUnit4.class)
+public class SystemFeaturesGeneratorApiTest {
+
+    @Rule public final MockitoRule mockito = MockitoJUnit.rule();
+
+    @Mock private Appendable mOut;
+
+    @Test
+    public void testEmpty() throws IOException {
+        final String[] args = new String[] {};
+        // This should just print the commandline and return.
+        SystemFeaturesGenerator.generate(args, mOut);
+        verify(mOut, never()).append(any());
+    }
+
+    @Test
+    public void testBasic() throws IOException {
+        final String[] args = new String[] {
+            "com.foo.Features",
+            "--feature=TELEVISION:0",
+        };
+        SystemFeaturesGenerator.generate(args, mOut);
+        verify(mOut, atLeastOnce()).append(any());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testInvalidFeatureVersion() throws IOException {
+        final String[] args = new String[] {
+            "com.foo.Features",
+            "--feature=TELEVISION:blarg",
+        };
+        SystemFeaturesGenerator.generate(args, mOut);
+        verify(mOut, never()).append(any());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testInvalidFeatureNameFromAndroidNamespace() throws IOException {
+        final String[] args = new String[] {
+            "com.foo.Features",
+            "--feature=android.hardware.doesntexist:0",
+        };
+        SystemFeaturesGenerator.generate(args, mOut);
+        verify(mOut, never()).append(any());
+    }
+}