Fix some downloads not being recognized

CHANGELOG.md

@@ -45,6 +45,7 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
 - Fixed a crash when opening the filters of a source with an invalid filter ([@AntsyLich](https://github.com/AntsyLich))
 - Fixed a crash when installing an extension on a device where the system installer can't ask for confirmation ([@AntsyLich](https://github.com/AntsyLich))
 - Fixed a crash when tapping in the long strip reader as it closed ([@AntsyLich](https://github.com/AntsyLich))
+- Fixed chapters downloaded before v0.21.0 showing as not downloaded when their name started with a space or dot, was long, or had a non-ASCII scanlator ([@AntsyLich](https://github.com/AntsyLich))
 
 ## [v0.21.1] - 2026-10-12
 ### Fixed

app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadProvider.kt

@@ -231,7 +231,7 @@ class DownloadProvider(
         enableChapterNameHash: Boolean = libraryPreferences.enableChapterNameHash.get(),
     ): String {
         return ChapterDirNameParts(chapterName, chapterScanlator, chapterUrl)
-            .dirName(disallowNonAsciiFilenames, enableChapterNameHash, sanitizeScanlator = true)
+            .dirName(disallowNonAsciiFilenames, enableChapterNameHash)
     }
 
     /**
@@ -254,14 +254,18 @@ class DownloadProvider(
         val booleanPairPermutation = listOf(false to false, false to true, true to false, true to true)
         val othersChapterDirNames = booleanPairPermutation
             .map { (disallowNonAsciiFilenames, enableChapterNameHash) ->
-                parts.dirName(disallowNonAsciiFilenames, enableChapterNameHash, sanitizeScanlator = true)
+                parts.dirName(disallowNonAsciiFilenames, enableChapterNameHash)
+            }
+        val splitChapterDirNames = booleanPairPermutation
+            .map { (disallowNonAsciiFilenames, enableChapterNameHash) ->
+                parts.splitDirName(disallowNonAsciiFilenames, enableChapterNameHash, sanitizeScanlator = true)
             }
 
         // Scanlators weren't sanitized for a while. One with a "/" nested its folder, so it was never found anyway.
         val scanlator = parts.chapterScanlator
         val unsanitizedScanlatorChapterDirNames = if (scanlator != null && '/' !in scanlator) {
             booleanPairPermutation.map { (disallowNonAsciiFilenames, enableChapterNameHash) ->
-                parts.dirName(disallowNonAsciiFilenames, enableChapterNameHash, sanitizeScanlator = false)
+                parts.splitDirName(disallowNonAsciiFilenames, enableChapterNameHash, sanitizeScanlator = false)
             }
         } else {
             emptyList()
@@ -272,6 +276,7 @@ class DownloadProvider(
             // chapter names)
             add(chapterNameV1)
             addAll(othersChapterDirNames)
+            addAll(splitChapterDirNames)
             addAll(unsanitizedScanlatorChapterDirNames)
         }
     }
@@ -291,7 +296,6 @@ class DownloadProvider(
         val chapterDirName = parts.dirName(
             disallowNonAscii = libraryPreferences.disallowNonAsciiFilenames.get(),
             enableHash = libraryPreferences.enableChapterNameHash.get(),
-            sanitizeScanlator = true,
         )
         val legacyChapterDirNames = getLegacyChapterDirNames(parts)
 
@@ -330,9 +334,29 @@ private class ChapterDirNameParts(chapterName: String, val chapterScanlator: Str
         chapterScanlator?.let { DiskUtil.buildValidFilename(it) }
     }
 
+    private val validDirNames = arrayOfNulls<String>(2)
+
     private val validChapterNames = arrayOfNulls<String>(2)
 
-    fun dirName(disallowNonAscii: Boolean, enableHash: Boolean, sanitizeScanlator: Boolean): String {
+    fun dirName(disallowNonAscii: Boolean, enableHash: Boolean): String {
+        val index = if (disallowNonAscii) 1 else 0
+        val dirName = validDirNames[index]
+            // The scanlator and the name are made valid together, as every version before 0.21.0 did
+            ?: DiskUtil.buildValidFilename(
+                if (chapterScanlator.isNullOrBlank()) chapterName else "${chapterScanlator}_$chapterName",
+                // Subtract 7 bytes for hash and underscore, 4 bytes for .cbz
+                DiskUtil.MAX_FILE_NAME_BYTES - 11,
+                disallowNonAscii,
+            )
+                .also { validDirNames[index] = it }
+        return if (enableHash) dirName + hashSuffix else dirName
+    }
+
+    /**
+     * The name 0.21.0 and 0.21.1 gave a chapter, which made only the chapter name valid and so differs for names
+     * starting with a space or dot, long names, and non-ASCII scanlators.
+     */
+    fun splitDirName(disallowNonAscii: Boolean, enableHash: Boolean, sanitizeScanlator: Boolean): String {
         return buildString {
             if (!chapterScanlator.isNullOrBlank()) {
                 // A "/" in the scanlator would otherwise nest the chapter in a folder of its own

app/src/test/java/eu/kanade/tachiyomi/data/download/DownloadProviderTest.kt

@@ -0,0 +1,73 @@
+package eu.kanade.tachiyomi.data.download
+
+import eu.kanade.tachiyomi.util.lang.Hash.md5
+import eu.kanade.tachiyomi.util.storage.DiskUtil
+import io.kotest.matchers.collections.shouldContain
+import io.kotest.matchers.shouldBe
+import io.mockk.mockk
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.MethodSource
+import tachiyomi.core.common.preference.InMemoryPreferenceStore
+import tachiyomi.domain.library.service.LibraryPreferences
+
+class DownloadProviderTest {
+
+    private fun provider(disallowNonAscii: Boolean): DownloadProvider {
+        val preferences = LibraryPreferences(InMemoryPreferenceStore())
+        preferences.disallowNonAsciiFilenames.set(disallowNonAscii)
+        preferences.enableChapterNameHash.set(true)
+        return DownloadProvider(mockk(relaxed = true), mockk(relaxed = true), preferences)
+    }
+
+    private fun dirNameBefore0210(name: String, scanlator: String?, url: String, disallowNonAscii: Boolean): String {
+        val dirName = if (scanlator.isNullOrBlank()) name else "${scanlator}_$name"
+        return DiskUtil.buildValidFilename(dirName, DiskUtil.MAX_FILE_NAME_BYTES - 11, disallowNonAscii) +
+            "_" + md5(url).take(6)
+    }
+
+    private fun dirName0210(name: String, scanlator: String?, url: String, disallowNonAscii: Boolean): String {
+        return DiskUtil.buildValidFilename(scanlator!!) + "_" +
+            DiskUtil.buildValidFilename(name, DiskUtil.MAX_FILE_NAME_BYTES - 11, disallowNonAscii) +
+            "_" + md5(url).take(6)
+    }
+
+    @ParameterizedTest
+    @MethodSource("chapters")
+    fun `finds chapters downloaded before 0_21_0 and names new ones the same`(
+        name: String,
+        scanlator: String?,
+        disallowNonAscii: Boolean,
+    ) {
+        val provider = provider(disallowNonAscii)
+        val expected = dirNameBefore0210(name, scanlator, URL, disallowNonAscii)
+
+        provider.getValidChapterDirNames(name, scanlator, URL) shouldContain expected
+        provider.getChapterDirName(name, scanlator, URL) shouldBe expected
+    }
+
+    @ParameterizedTest
+    @MethodSource("chapters")
+    fun `finds chapters downloaded by 0_21_0 and 0_21_1`(name: String, scanlator: String?, disallowNonAscii: Boolean) {
+        if (scanlator.isNullOrBlank()) return
+
+        provider(disallowNonAscii).getValidChapterDirNames(name, scanlator, URL) shouldContain
+            dirName0210(name, scanlator, URL, disallowNonAscii)
+    }
+
+    companion object {
+        private const val URL = "/chapter/1"
+
+        @JvmStatic
+        fun chapters() = listOf(
+            Arguments.of("Chapter 1", "Group", false),
+            Arguments.of(" Chapter 1", "Group", false),
+            Arguments.of(".Chapter 1", "Group", false),
+            Arguments.of("Chapter 1", "Group ", false),
+            Arguments.of("Chapter 1", "A/B ", false),
+            Arguments.of("Chapter ".repeat(40), "Group", false),
+            Arguments.of("Chapter 1", "翻訳グループ", true),
+            Arguments.of(" Chapter 1", null, false),
+        )
+    }
+}