Now launcher has a nice launch ui and it can launch MiNeCRaFt.

core_lib/game/version_info.py

@@ -306,11 +306,16 @@ def fetch_specific_version_manifest(version_manifest: dict, spec_version: str) -
 # mapping
 get_specific_version_manifest = fetch_specific_version_manifest
 
-def find_useful_part_in_specific_version_manifest(spec_version_manifest: dict)\
+def default_java_version():
+    return {"component": "jre-legacy", "majorVersion": 8}
+
+def find_useful_part_in_specific_version_manifest(spec_version_manifest: dict,
+                                                  failback_java_version: dict | None=None) \
         -> tuple[dict | None, dict | None, dict | None, dict | None, list | None, str | None, str | None]:
     """
     Return useful part from version manifest.
     :param spec_version_manifest: Specific version's data
+    :param failback_java_version: Failback java version data (default is Java 8)
     :return:
         arguments: dict (contains jvm and game args, for newer version of Minecraft)
         asset_index: dict
@@ -323,11 +328,15 @@ def find_useful_part_in_specific_version_manifest(spec_version_manifest: dict)\
     arguments = spec_version_manifest.get("arguments", {})
     asset_index = spec_version_manifest.get("assetIndex", {})
     downloads = spec_version_manifest.get("downloads", {})
-    java_version = spec_version_manifest.get("javaVersion", {})
     libraries = spec_version_manifest.get("libraries", [])
     main_class = spec_version_manifest.get("mainClass", None)
     legacy_game_args = spec_version_manifest.get("minecraftArguments", None)
 
+    if failback_java_version is None:
+        failback_java_version = default_java_version()
+
+    java_version = spec_version_manifest.get("javaVersion", failback_java_version)
+
     if not arguments and not legacy_game_args:
         raise VersionDataKeyNotFoundException(
             "No version manifest available in version manifest. (\"arguments\" or \"minecraftArguments\")"
@@ -500,4 +509,10 @@ def download_core_file(manifest: dict, destination: Path, is_server=False, raise
             "Core file url is None. Unable to download it."
         )
 
-    return file
+    return file
+
+
+LATEST_VERSION_ALIASES = {
+    "latest-release": {"displayName": "Latest Release"},
+    "latest-snapshot": {"displayName": "Latest Snapshot"},
+}

core_lib/qt/messagebox.py

@@ -46,6 +46,38 @@ def warning(parent: QWidget, title: str, message: str,
     ).exec()
 
 
+def error_with_plain_text(
+    parent: QWidget,
+    title: str,
+    message: str,
+    content: str,
+) -> None:
+    dialog = QDialog(parent)
+    dialog.setWindowTitle(title)
+    dialog.resize(720, 420)
+
+    layout = QVBoxLayout(dialog)
+
+    label = QLabel(message)
+    label.setWordWrap(True)
+
+    details_box = QPlainTextEdit()
+    details_box.setReadOnly(True)
+    details_box.setPlainText(content)
+    details_box.setSizePolicy(
+        QSizePolicy.Policy.Expanding,
+        QSizePolicy.Policy.Expanding,
+    )
+
+    buttons = QDialogButtonBox(QDialogButtonBox.StandardButton.Ok)
+    buttons.accepted.connect(dialog.accept)
+
+    layout.addWidget(label)
+    layout.addWidget(details_box, 1)
+    layout.addWidget(buttons)
+    dialog.exec()
+
+
 def ask_yes_no_with_plain_text(parent: QWidget, title: str, message: str, content: str):
     dialog = QDialog(parent)
     dialog.setWindowTitle(title)