[Text Consistency] Improve consecutive newlines cleaning

NewlineNormalizer replaces consecutive newlines with a single newline in the input text.
This also catches whitespace characters.
Fixes: 337021118
Test: NewlineNormalizerTest
Flag: ACONFIG android.app.Flags.clean_up_spans_and_new_lines STAGING

Change-Id: Id0d0ec324ba40ce7f1acf9dd9b712f46b8ed1431

3 files changed, 112 insertions, 1 deletions

diff --git a/core/java/android/app/Notification.java b/core/java/android/app/Notification.java
index 05a2aece789f..60ae65b0546c 100644
--- a/core/java/android/app/Notification.java
+++ b/core/java/android/app/Notification.java
@@ -115,6 +115,7 @@ import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.graphics.ColorUtils;
 import com.android.internal.util.ArrayUtils;
 import com.android.internal.util.ContrastColorUtil;
+import com.android.internal.util.NewlineNormalizer;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -3187,7 +3188,7 @@ public class Notification implements Parcelable
             return charSequence;
         }
 
-        return charSequence.toString().replaceAll("[\r\n]+", "\n");
+        return NewlineNormalizer.normalizeNewlines(charSequence.toString());
     }
 
     private static CharSequence removeTextSizeSpans(CharSequence charSequence) {
diff --git a/core/java/com/android/internal/util/NewlineNormalizer.java b/core/java/com/android/internal/util/NewlineNormalizer.java
new file mode 100644
index 000000000000..0104d1f56f83
--- /dev/null
+++ b/core/java/com/android/internal/util/NewlineNormalizer.java
@@ -0,0 +1,39 @@
+/*
+ * 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.internal.util;
+
+
+import java.util.regex.Pattern;
+
+/**
+ * Utility class that replaces consecutive empty lines with single new line.
+ * @hide
+ */
+public class NewlineNormalizer {
+
+    private static final Pattern MULTIPLE_NEWLINES = Pattern.compile("\\v(\\s*\\v)?");
+
+    // Private constructor to prevent instantiation
+    private NewlineNormalizer() {}
+
+    /**
+     * Replaces consecutive newlines with a single newline in the input text.
+     */
+    public static String normalizeNewlines(String text) {
+        return MULTIPLE_NEWLINES.matcher(text).replaceAll("\n");
+    }
+}
diff --git a/core/tests/utiltests/src/com/android/internal/util/NewlineNormalizerTest.java b/core/tests/utiltests/src/com/android/internal/util/NewlineNormalizerTest.java
new file mode 100644
index 000000000000..bcdac610a49d
--- /dev/null
+++ b/core/tests/utiltests/src/com/android/internal/util/NewlineNormalizerTest.java
@@ -0,0 +1,71 @@
+/*
+ * 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.internal.util;
+
+import static junit.framework.Assert.assertEquals;
+
+
+import android.platform.test.annotations.DisabledOnRavenwood;
+import android.platform.test.ravenwood.RavenwoodRule;
+
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * Test for {@link NewlineNormalizer}
+ * @hide
+ */
+@DisabledOnRavenwood(blockedBy = NewlineNormalizer.class)
+@RunWith(AndroidJUnit4.class)
+public class NewlineNormalizerTest {
+
+    @Rule
+    public final RavenwoodRule mRavenwood = new RavenwoodRule();
+
+    @Test
+    public void testEmptyInput() {
+        assertEquals("", NewlineNormalizer.normalizeNewlines(""));
+    }
+
+    @Test
+    public void testSingleNewline() {
+        assertEquals("\n", NewlineNormalizer.normalizeNewlines("\n"));
+    }
+
+    @Test
+    public void testMultipleConsecutiveNewlines() {
+        assertEquals("\n", NewlineNormalizer.normalizeNewlines("\n\n\n\n\n"));
+    }
+
+    @Test
+    public void testNewlinesWithSpacesAndTabs() {
+        String input = "Line 1\n  \n \t \n\tLine 2";
+        // Adjusted expected output to include the tab character
+        String expected = "Line 1\n\tLine 2";
+        assertEquals(expected, NewlineNormalizer.normalizeNewlines(input));
+    }
+
+    @Test
+    public void testMixedNewlineCharacters() {
+        String input = "Line 1\r\nLine 2\u000BLine 3\fLine 4\u2028Line 5\u2029Line 6";
+        String expected = "Line 1\nLine 2\nLine 3\nLine 4\nLine 5\nLine 6";
+        assertEquals(expected, NewlineNormalizer.normalizeNewlines(input));
+    }
+}