test: unit test for normalizeForSearch

- extract method to extension file

AnkiDroid/src/main/java/com/ichi2/anki/CardBrowser.kt

@@ -382,7 +382,6 @@ open class CardBrowser :
         )
 
         val launchOptions = intent?.toCardBrowserLaunchOptions() // must be called after super.onCreate()
-
         // must be called once we have an accessible collection
         viewModel = createViewModel(launchOptions)
 

AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserViewModel.kt

@@ -47,6 +47,7 @@ import com.ichi2.anki.model.CardsOrNotes.NOTES
 import com.ichi2.anki.model.SortType
 import com.ichi2.anki.pages.CardInfoDestination
 import com.ichi2.anki.preferences.SharedPreferencesProvider
+import com.ichi2.anki.utils.ext.normalizeForSearch
 import com.ichi2.annotations.NeedsTest
 import com.ichi2.libanki.Card
 import com.ichi2.libanki.CardId
@@ -85,9 +86,7 @@ import java.io.DataOutputStream
 import java.io.File
 import java.io.FileInputStream
 import java.io.FileOutputStream
-import java.text.Normalizer
 import java.util.Collections
-import java.util.regex.Pattern
 import kotlin.math.max
 import kotlin.math.min
 
@@ -969,11 +968,6 @@ class CardBrowserViewModel(
 
     private suspend fun shouldIgnoreAccents() = withCol { config.getBool(ConfigKey.Bool.IGNORE_ACCENTS_IN_SEARCH) }
 
-    private fun String.normalizeForSearch(): String {
-        val normalized = Normalizer.normalize(this, Normalizer.Form.NFD)
-        return Pattern.compile("\\p{InCombiningDiacriticalMarks}+").matcher(normalized).replaceAll("")
-    }
-
     /**
      * @see com.ichi2.anki.searchForRows
      */

AnkiDroid/src/main/java/com/ichi2/anki/utils/ext/String.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2025 Ashish Yadav <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.ichi2.anki.utils.ext
+
+import java.text.Normalizer
+import java.util.regex.Pattern
+
+private val DIACRITICAL_MARKS_PATTERN = Pattern.compile("\\p{InCombiningDiacriticalMarks}+")
+
+/**
+ * Normalizes the given string by removing diacritical marks (accents) to enable accent-insensitive searches.
+ *
+ * This method uses Unicode normalization in **NFD (Normalization Form Decomposition)** mode, which separates
+ * base characters from their diacritical marks. Then, it removes all combining diacritical marks using a regex.
+ *
+ * Example usage:
+ * ```
+ * val input = "café naïve résumé"
+ * val normalized = input.normalizeForSearch()
+ * println(normalized) // Output: "cafe naive resume"
+ * ```
+ *
+ * @receiver The input string that may contain accented characters.
+ * @return A new string with accents removed.
+ */
+fun String.normalizeForSearch(): String {
+    val normalized = Normalizer.normalize(this, Normalizer.Form.NFD)
+    return DIACRITICAL_MARKS_PATTERN.matcher(normalized).replaceAll("")
+}

AnkiDroid/src/main/res/xml/preferences_general.xml

@@ -24,7 +24,6 @@
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
-    xmlns:app1="urn:oasis:names:tc:xliff:document:1.2"
     android:title="@string/pref_cat_general"
     android:key="@string/pref_general_screen_key">
         <ListPreference

AnkiDroid/src/test/java/com/ichi2/anki/browser/CardBrowserViewModelTest.kt

@@ -59,6 +59,7 @@ import com.ichi2.anki.model.SortType.SORT_FIELD
 import com.ichi2.anki.servicelayer.NoteService
 import com.ichi2.anki.setFlagFilterSync
 import com.ichi2.anki.utils.ext.ifNotZero
+import com.ichi2.anki.utils.ext.normalizeForSearch
 import com.ichi2.libanki.CardId
 import com.ichi2.libanki.DeckId
 import com.ichi2.libanki.Note
@@ -81,8 +82,11 @@ import org.hamcrest.Matchers.hasSize
 import org.hamcrest.Matchers.lessThan
 import org.hamcrest.Matchers.not
 import org.hamcrest.Matchers.nullValue
+import org.junit.Assert.assertEquals
 import org.junit.Test
 import org.junit.jupiter.api.assertInstanceOf
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.CsvSource
 import org.junit.runner.RunWith
 import timber.log.Timber
 import java.io.File
@@ -552,6 +556,21 @@ class CardBrowserViewModelTest : JvmTest() {
             }
         }
 
+    @ParameterizedTest
+    @CsvSource(
+        "café Ábaco naïve résumé, cafe Abaco naive resume",
+        "élégant déjà vu, elegant deja vu",
+        "hello world, hello world",
+        "'', ''",
+        "1234!@# café, 1234!@# cafe",
+    )
+    fun `test normalizeForSearch`(
+        input: String,
+        expected: String,
+    ) {
+        assertEquals(expected, input.normalizeForSearch())
+    }
+
     @Test
     fun `suspend - notes - no selection`() =
         runViewModelNotesTest(notes = 2) {