Fix nullability issues for testutil.truth

PiperOrigin-RevId: 289658098

testutils/build.gradle

@@ -36,6 +36,8 @@ dependencies {
     api 'androidx.test.ext:junit:' + androidxTestJUnitVersion
     api 'junit:junit:' + junitVersion
     api 'com.google.truth:truth:' + truthVersion
+    compileOnly 'org.checkerframework:checker-qual:' + checkerframeworkVersion
+    compileOnly 'org.checkerframework:checker-compat-qual:' + checkerframeworkVersion
     implementation 'androidx.annotation:annotation:' + androidxAnnotationVersion
     implementation project(modulePrefix + 'library-core')
     testImplementation project(modulePrefix + 'testutils')

testutils/src/main/java/com/google/android/exoplayer2/testutil/truth/SpannedSubject.java

@@ -45,6 +45,8 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import org.checkerframework.checker.nullness.compatqual.NullableType;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /** A Truth {@link Subject} for assertions on {@link Spanned} instances containing text styling. */
 // TODO: add support for more Spans i.e. all those used in com.google.android.exoplayer2.text.
@@ -74,6 +76,11 @@ public final class SpannedSubject extends Subject {
   }
 
   public void hasNoSpans() {
+    if (actual == null) {
+      failWithoutActual(simpleFact("Spanned must not be null"));
+      return;
+    }
+
     Object[] spans = actual.getSpans(0, actual.length(), Object.class);
     if (spans.length > 0) {
       failWithoutActual(
@@ -599,7 +606,8 @@ public final class SpannedSubject extends Subject {
       failWithoutActual(simpleFact("Spanned must not be null"));
       return;
     }
-    Object[] matchingSpans = actual.getSpans(start, end, spanClazz);
+
+    @NullableType Object[] matchingSpans = actual.getSpans(start, end, spanClazz);
     if (matchingSpans.length != 0) {
       failWithoutActual(
           simpleFact(
@@ -612,15 +620,21 @@ public final class SpannedSubject extends Subject {
   }
 
   private <T> List<T> findMatchingSpans(int startIndex, int endIndex, Class<T> spanClazz) {
+    if (actual == null) {
+      failWithoutActual(simpleFact("Spanned must not be null"));
+      return Collections.emptyList();
+    }
+
     List<T> spans = new ArrayList<>();
     for (T span : actual.getSpans(startIndex, endIndex, spanClazz)) {
       if (actual.getSpanStart(span) == startIndex && actual.getSpanEnd(span) == endIndex) {
         spans.add(span);
       }
     }
-    return spans;
+    return Collections.unmodifiableList(spans);
   }
 
+  @RequiresNonNull("actual")
   private void failWithExpectedSpan(
       int start, int end, Class<?> spanType, String spannedSubstring) {
     failWithoutActual(
@@ -887,7 +901,7 @@ public final class SpannedSubject extends Subject {
     @Override
     public AndSpanFlags withFamily(String fontFamily) {
       List<Integer> matchingSpanFlags = new ArrayList<>();
-      List<String> spanFontFamilies = new ArrayList<>();
+      List<@NullableType String> spanFontFamilies = new ArrayList<>();
 
       for (TypefaceSpan span : actualSpans) {
         spanFontFamilies.add(span.getFamily());
@@ -1059,7 +1073,7 @@ public final class SpannedSubject extends Subject {
       }
 
       @Override
-      public boolean equals(Object o) {
+      public boolean equals(@Nullable Object o) {
         if (this == o) {
           return true;
         }

testutils/src/main/java/com/google/android/exoplayer2/testutil/truth/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.testutil.truth;
+
+import com.google.android.exoplayer2.util.NonNullApi;