[CLI] Raise explicit error for shell-script extensions on Windows (#4846)

* [CLI] Raise explicit error for shell-script extensions on Windows

* [CLI] Surface install errors from extension auto-install

* [CLI] Drop Windows-specific extension install tests

Author: hanouticelina

docs/source/en/guides/cli-extensions.md

@@ -39,6 +39,10 @@ falls back to installing the repo as a Python package.
 A shell script extension is the simplest type. You only need a GitHub repository with an executable file
 named `hf-<name>` at the root.
 
+> [!WARNING]
+> Shell script extensions are not supported on Windows. If your extension must work on Windows, make it a
+> [Python extension](#create-a-python-extension) instead.
+
 ### Minimal example
 
 Create a repository named `hf-hello` on GitHub with a single file:

src/huggingface_hub/cli/extensions.py

@@ -375,11 +375,8 @@ def _auto_install_official_extension(short_name: str) -> Path | None:
         out.confirm(f"'{short_name}' is an official Hugging Face extension ({owner}/{repo_name}). Install it?")
     except ConfirmationError:
         return None
-    try:
-        manifest = _install_extension(owner=owner, repo_name=repo_name, short_name=short_name)
-        return Path(manifest.executable_path).expanduser()
-    except Exception:
-        return None
+    manifest = _install_extension(owner=owner, repo_name=repo_name, short_name=short_name)
+    return Path(manifest.executable_path).expanduser()
 
 
 def _load_installed_extension_for_update(name: str) -> ExtensionManifest:
@@ -435,6 +432,11 @@ def _install_extension(
             binary = None
 
         if binary is not None:
+            if os.name == "nt":
+                raise CLIError(
+                    f"'{owner}/{repo_name}' is a shell-script extension, which is not supported on Windows. "
+                    "Only Python extensions can be installed on Windows."
+                )
             executable_path = _install_binary_extension(
                 extension_dir=extension_dir, short_name=short_name, binary=binary
             )
@@ -500,8 +502,7 @@ def _fetch_latest_commit_sha(*, owner: str, repo_name: str) -> str:
 
 
 def _fetch_remote_binary(*, owner: str, repo_name: str, short_name: str) -> bytes:
-    executable_name = _get_executable_name(short_name)
-    raw_url = f"https://raw.githubusercontent.com/{owner}/{repo_name}/HEAD/{executable_name}"
+    raw_url = f"https://raw.githubusercontent.com/{owner}/{repo_name}/HEAD/hf-{short_name}"
     response = _github_request("GET", raw_url)
     return response.content
 

tests/test_cli.py

@@ -5140,6 +5140,7 @@ def test_unknown_command_spends_no_api_quota(self, github: _FakeGitHubSession) -
             ("Contribute to huggingface/hf-demo development by creating an account on GitHub.", None),
         ],
     )
+    @pytest.mark.skipif(os.name == "nt", reason="Shell-script extensions are not supported on Windows.")
     def test_install_uses_head_refs_and_a_single_api_call(
         self, github: _FakeGitHubSession, about: str, expected_description: str | None
     ) -> None:
@@ -5161,6 +5162,7 @@ def test_install_uses_head_refs_and_a_single_api_call(
         raw_urls = [url for url in github.urls if url.startswith(raw_prefix)]
         assert raw_urls and all(url.removeprefix(raw_prefix).startswith("HEAD/") for url in raw_urls)
 
+    @pytest.mark.skipif(os.name == "nt", reason="Shell-script extensions are not supported on Windows.")
     def test_install_completes_when_the_api_quota_is_exhausted(self, github: _FakeGitHubSession) -> None:
         # The extension itself comes from the CDN, so only the optional version marker is lost.
         github.responses = {