Improve Flutter SDK installation and detection

Refactored Flutter SDK installation logic to prompt users before installing if the SDK is missing or invalid, and added get_flutter_dir utility for consistent SDK path resolution. Enhanced batch file detection to check the expected install directory first, and standardized user prompts for SDK installation.

Author: FeodorFitsner

sdk/python/packages/flet-cli/src/flet_cli/commands/flutter_base.py

@@ -18,6 +18,7 @@
 from flet.utils import cleanup_path, is_windows
 from flet.utils.platform_utils import get_bool_env_var
 from flet_cli.commands.base import BaseCommand
+from flet_cli.utils.flutter import get_flutter_dir, install_flutter
 
 PYODIDE_ROOT_URL = "https://cdn.jsdelivr.net/pyodide/v0.27.7/full"
 DEFAULT_TEMPLATE_URL = "gh:flet-dev/flet-build-template"
@@ -118,6 +119,24 @@ def initialize_command(self):
             or not self.dart_exe
             or not self.flutter_version_valid()
         ):
+            if not self.assume_yes:
+                console.log(
+                    "Flutter SDK not found or invalid version installed.",
+                    style=warning_style,
+                )
+                prompt = (
+                    "Flutter SDK "
+                    f"{MINIMAL_FLUTTER_VERSION} is required. It will be installed now. "
+                    "Proceed? [y/n] "
+                )
+
+                if not self._prompt_input(prompt):
+                    self.skip_flutter_doctor = True
+                    self.cleanup(
+                        1,
+                        "Flutter SDK installation is required. "
+                        "Re-run with --yes to install automatically.",
+                    )
             self.install_flutter()
 
         if self.verbose > 0:
@@ -164,7 +183,6 @@ def install_flutter(self):
         self.update_status(
             f"[bold blue]Installing Flutter {MINIMAL_FLUTTER_VERSION}..."
         )
-        from flet_cli.utils.flutter import install_flutter
 
         flutter_dir = install_flutter(
             str(MINIMAL_FLUTTER_VERSION), self.log_stdout, progress=self.progress
@@ -270,7 +288,7 @@ def _confirm_android_sdk_installation(self) -> bool:
 
         prompt = (
             "\nAndroid SDK is required. If it's missing or incomplete, "
-            "it will be installed now. Proceed? [y/N] "
+            "it will be installed now. Proceed? [y/n] "
         )
 
         if self._prompt_input(prompt):
@@ -286,6 +304,12 @@ def _prompt_input(self, prompt: str) -> bool:
             self.live.start()
 
     def find_flutter_batch(self, exe_filename: str):
+        install_dir = get_flutter_dir(str(MINIMAL_FLUTTER_VERSION))
+        ext = ".bat" if is_windows() else ""
+        batch_path = os.path.join(install_dir, "bin", f"{exe_filename}{ext}")
+        if os.path.exists(batch_path):
+            return batch_path
+
         batch_path = shutil.which(exe_filename)
         if not batch_path:
             return None

sdk/python/packages/flet-cli/src/flet_cli/utils/flutter.py

@@ -4,10 +4,11 @@
 from pathlib import Path
 from typing import Optional
 
-from flet_cli.utils.distros import download_with_progress, extract_with_progress
 from rich.console import Console
 from rich.progress import Progress
 
+from flet_cli.utils.distros import download_with_progress, extract_with_progress
+
 
 def get_flutter_url(version):
     """Determines the Flutter archive URL based on the platform."""
@@ -28,9 +29,14 @@ def get_flutter_url(version):
         raise ValueError(f"Unsupported platform: {system}")
 
 
+def get_flutter_dir(version):
+    home_dir = Path.home()
+    return os.path.join(home_dir, "flutter", version)
+
+
 def install_flutter(version, log, progress: Optional[Progress] = None):
+    install_dir = get_flutter_dir(version)
     home_dir = Path.home()
-    install_dir = os.path.join(home_dir, "flutter", version)
 
     if not os.path.exists(install_dir):
         url = get_flutter_url(version)