From c16bba7a83761589745299bd28807a588c2f3870 Mon Sep 17 00:00:00 2001
From: Jan Sebechlebsky <jsebechlebsky@google.com>
Date: Wed, 12 Oct 2022 19:07:24 +0200
Subject: [PATCH] Throw exception when attempting to build empty
 AudioMixingRule.

This fixes
android.media.audio.cts.AudioPlaybackCaptureTest#testMatchNothing.

The test asserts that attempting to capture playback with no
criteria specified throws and Exception. However, the reason why
the test was passing and Exception thrown was not because of
explicit check for empty AudioMixingRule, but because of
invalid mix role (not adding any rules prior to ag/20001744
caused mix type not to be inferred). If the mix role was
explicitly set for the AudioMixingRule.Builder the test would
also fail the expectation.
This cl is adding explicit check for the presence of rules when
building AudioMixingRule to fix this.

Bug: 252822301
Test: atest AudioPlaybackCaptureTest
Change-Id: If3caa635b67eca779bb2026d2da1c4727e4636e9
---
 media/java/android/media/audiopolicy/AudioMixingRule.java   | 4 ++++
 .../android/audiopolicytest/AudioMixingRuleUnitTests.java   | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/media/java/android/media/audiopolicy/AudioMixingRule.java b/media/java/android/media/audiopolicy/AudioMixingRule.java
index 08655ca6ad6b0..9c0b825fbfa30 100644
--- a/media/java/android/media/audiopolicy/AudioMixingRule.java
+++ b/media/java/android/media/audiopolicy/AudioMixingRule.java
@@ -704,8 +704,12 @@ public class AudioMixingRule {
          * Combines all of the matching and exclusion rules that have been set and return a new
          * {@link AudioMixingRule} object.
          * @return a new {@link AudioMixingRule} object
+         * @throws IllegalArgumentException if the rule is empty.
          */
         public AudioMixingRule build() {
+            if (mCriteria.isEmpty()) {
+                throw new IllegalArgumentException("Cannot build AudioMixingRule with no rules.");
+            }
             return new AudioMixingRule(
                     mTargetMixType == AudioMix.MIX_TYPE_INVALID
                             ? AudioMix.MIX_TYPE_PLAYERS : mTargetMixType,
diff --git a/media/tests/AudioPolicyTest/src/com/android/audiopolicytest/AudioMixingRuleUnitTests.java b/media/tests/AudioPolicyTest/src/com/android/audiopolicytest/AudioMixingRuleUnitTests.java
index a83e7d3a6ef1a..3cbfd50ff859e 100644
--- a/media/tests/AudioPolicyTest/src/com/android/audiopolicytest/AudioMixingRuleUnitTests.java
+++ b/media/tests/AudioPolicyTest/src/com/android/audiopolicytest/AudioMixingRuleUnitTests.java
@@ -212,6 +212,12 @@ public class AudioMixingRuleUnitTests {
                 containsInAnyOrder(isAudioMixSessionCriterion(TEST_SESSION_ID)));
     }
 
+    @Test
+    public void audioMixingRuleWithNoRulesFails() {
+        assertThrows(IllegalArgumentException.class,
+                () -> new AudioMixingRule.Builder().build());
+    }
+
 
     private static Matcher isAudioMixUidCriterion(int uid, boolean exclude) {
         return new CustomTypeSafeMatcher<AudioMixMatchCriterion>("uid mix criterion") {