Launch the executable a Store package declares (#400)

Store and GDK folders name their game in MicrosoftGame.config or
appxmanifest.xml. Picking the top-level Unreal bootstrap instead failed
with "CreateProcess() returned 2" when the Store had renamed the
shipping exe.

Co-authored-by: xXJsonDeruloXx <danielhimebauch@gmail.com>

app/src/main/java/com/droiddeck/launcher/frontend/AddedGames.kt

@@ -98,18 +98,26 @@ object AddedGames {
         return null
     }
 
-    /** The .exe files a game folder offers, best first ([GameExePicker]); also what its exe box lists, in that order. */
+    /** The .exe files a game folder offers, best first ([GameExePicker]); declared Store exes lead. */
     fun candidates(folder: File): List<File> = rank(folder).exes
 
-    /** [GameExePicker]'s ranking of [folder], without the names this list never offers. */
+    /** [GameExePicker]'s ranking, with a Store-declared executable taking precedence when present. */
     fun rank(folder: File): GameExePicker.Ranking {
         val key = "${folder.path}|${folder.lastModified()}"
         val now = System.currentTimeMillis()
         ranked[key]?.takeIf { now - it.first < RANK_FRESH_MS }?.let { return it.second }
-        return GameExePicker.rank(folder) { !SKIP.matches(it.name) }.also {
-            if (ranked.size > 256) ranked.clear()
-            ranked[key] = now to it
-        }
+        val guessed = GameExePicker.rank(folder) { !SKIP.matches(it.name) }
+        val declared = declaredExes(folder)
+        val preferred = declared.map { it.path }.toSet()
+        val result = if (declared.isEmpty()) guessed else GameExePicker.Ranking(
+            declared + guessed.exes.filter { it.path !in preferred },
+            List(declared.size) { Int.MAX_VALUE } + guessed.exes.zip(guessed.scores)
+                .filter { it.first.path !in preferred }.map { it.second },
+            uncertain = false,
+        )
+        if (ranked.size > 256) ranked.clear()
+        ranked[key] = now to result
+        return result
     }
 
     /** A folder's ranking for a minute, so one add (rank, then the game built from it) walks it once. */
@@ -160,6 +168,24 @@ object AddedGames {
             else -> peName
         }
     }
+    /** The executables MicrosoftGame.config or appxmanifest.xml declares that exist inside [folder]. */
+    internal fun declaredExes(folder: File): List<File> {
+        val names = DECLARED.flatMap { (file, pattern) ->
+            runCatching { pattern.findAll(File(folder, file).readText()).map { it.groupValues[1] }.toList() }.getOrDefault(emptyList())
+        }
+        val root = runCatching { folder.canonicalPath + File.separator }.getOrNull() ?: return emptyList()
+        return names.asSequence()
+            .map { File(folder, it.trim().replace('\\', '/').trimStart('/')) }
+            .filter { it.name.endsWith(".exe", ignoreCase = true) && !SKIP.matches(it.name) && it.isFile }
+            .filter { runCatching { it.canonicalPath.startsWith(root) }.getOrDefault(false) }
+            .distinctBy { it.path }
+            .toList()
+    }
+
+    private val DECLARED = listOf(
+        "MicrosoftGame.config" to Regex("<Executable\\b[^>]*?\\bName\\s*=\\s*\"([^\"]+)\"", RegexOption.IGNORE_CASE),
+        "appxmanifest.xml" to Regex("<Application\\b[^>]*?\\bExecutable\\s*=\\s*\"([^\"]+)\"", RegexOption.IGNORE_CASE),
+    )
 
     fun scan(context: Context): List<Game> {
         val out = ArrayList<Game>()

app/src/test/java/com/droiddeck/launcher/frontend/AddedGamesScanTest.kt

@@ -27,4 +27,45 @@ class AddedGamesScanTest {
         SessionPrefs.setAddedGamesDirs(app, listOf(games.path))
         assertEquals(listOf("Example"), AddedGames.scan(app).map { it.name })
     }
+
+    @Test fun aStorePackageLaunchesTheExecutableItDeclares() {
+        val game = tmp.newFolder("Minecraft Dungeons")
+        File(game, "Dungeons.exe").writeText("unreal bootstrap")
+        File(game, "Dungeons/Binaries/Win64").mkdirs()
+        File(game, "Dungeons/Binaries/Win64/Dungeons.exe").writeText("the game, renamed from Dungeons-Win64-Shipping.exe")
+        File(game, "MicrosoftGame.config").writeText(
+            "<Game><ExecutableList>\n  <Executable Name=\"Dungeons\\Binaries\\Win64\\Dungeons.exe\"\n\n    Id=\"Game\" />\n</ExecutableList></Game>",
+        )
+        assertEquals(File(game, "Dungeons/Binaries/Win64/Dungeons.exe").path, AddedGames.candidates(game).first().path)
+        assertEquals(2, AddedGames.candidates(game).size)
+    }
+
+    @Test fun anAppxManifestNamesTheGameWhenThereIsNoConfig() {
+        val game = tmp.newFolder("Store Game")
+        File(game, "Launcher.exe").writeText("bootstrap")
+        File(game, "Game/Binaries/Win64").mkdirs()
+        File(game, "Game/Binaries/Win64/Game.exe").writeText("game")
+        File(game, "appxmanifest.xml").writeText("<Package><Applications><Application Id=\"Game\" Executable=\"Game\\Binaries\\Win64\\Game.exe\" /></Applications></Package>")
+        assertEquals(File(game, "Game/Binaries/Win64/Game.exe").path, AddedGames.candidates(game).first().path)
+    }
+
+    @Test fun aDeclaredTopLevelExecutableKeepsItsPlace() {
+        val game = tmp.newFolder("Minecraft Dungeons II")
+        File(game, "Dungeons.exe").writeText("bootstrap")
+        File(game, "Other.exe").writeText("a much longer other executable")
+        File(game, "MicrosoftGame.config").writeText("<Executable Name=\"Dungeons.exe\" Id=\"App\" />")
+        assertEquals(listOf("Dungeons.exe", "Other.exe"), AddedGames.candidates(game).map { it.name })
+    }
+
+    @Test fun declaredHelpersMissingFilesAndPathsOutsideTheFolderAreIgnored() {
+        val game = tmp.newFolder("Pass Game")
+        File(game, "PassGame.exe").writeText("game")
+        File(game, "gamelaunchhelper.exe").writeText("needs gaming services")
+        tmp.newFile("Outside.exe").writeText("not this game")
+        File(game, "MicrosoftGame.config").writeText(
+            "<Executable Name=\"gamelaunchhelper.exe\" /><Executable Name=\"Missing.exe\" /><Executable Name=\"..\\Outside.exe\" />",
+        )
+        assertEquals(emptyList<File>(), AddedGames.declaredExes(game))
+        assertEquals(listOf("PassGame.exe"), AddedGames.candidates(game).map { it.name })
+    }
 }