Frontend Manager: avoid redundant gh calls for static versions (#5152)

* Frontend Manager: avoid redundant gh calls for static versions

* actually, removing old tmpdir isn't needed

I tested - downloader code handles this case well already
(also rmdir was wrong func anyway, needed shutil.rmtree if it had content)

* add code comment

app/frontend_management.py

@@ -151,6 +151,15 @@ def init_frontend_unsafe(cls, version_string: str, provider: Optional[FrontEndPr
             return cls.DEFAULT_FRONTEND_PATH
 
         repo_owner, repo_name, version = cls.parse_version_string(version_string)
+
+        if version.startswith("v"):
+            expected_path = str(Path(cls.CUSTOM_FRONTENDS_ROOT) / f"{repo_owner}_{repo_name}" / version.lstrip("v"))
+            if os.path.exists(expected_path):
+                logging.info(f"Using existing copy of specific frontend version tag: {repo_owner}/{repo_name}@{version}")
+                return expected_path
+
+        logging.info(f"Initializing frontend: {repo_owner}/{repo_name}@{version}, requesting version details from GitHub...")
+
         provider = provider or FrontEndProvider(repo_owner, repo_name)
         release = provider.get_release(version)
 
@@ -159,16 +168,20 @@ def init_frontend_unsafe(cls, version_string: str, provider: Optional[FrontEndPr
             Path(cls.CUSTOM_FRONTENDS_ROOT) / provider.folder_name / semantic_version
         )
         if not os.path.exists(web_root):
+            # Use tmp path until complete to avoid path exists check passing from interrupted downloads
+            tmp_path = web_root + ".tmp"
             try:
-                os.makedirs(web_root, exist_ok=True)
+                os.makedirs(tmp_path, exist_ok=True)
                 logging.info(
                     "Downloading frontend(%s) version(%s) to (%s)",
                     provider.folder_name,
                     semantic_version,
-                    web_root,
+                    tmp_path,
                 )
                 logging.debug(release)
-                download_release_asset_zip(release, destination_path=web_root)
+                download_release_asset_zip(release, destination_path=tmp_path)
+                if os.listdir(tmp_path):
+                    os.rename(tmp_path, web_root)
             finally:
                 # Clean up the directory if it is empty, i.e. the download failed
                 if not os.listdir(web_root):