cache packages_distributions (#11453)

* cache packages_distributions

* remove unused exception reference

* make style
Signed-off-by: Vladimir Mandic <mandic00@live.com>

* change name to _package_map

---------
Signed-off-by: Vladimir Mandic <mandic00@live.com>
Co-authored-by: DN6 <dhruv.nair@gmail.com>

src/diffusers/utils/import_utils.py

@@ -36,7 +36,10 @@ if sys.version_info < (3, 8):
     import importlib_metadata
 else:
     import importlib.metadata as importlib_metadata
-
+try:
+    _package_map = importlib_metadata.packages_distributions()  # load-once to avoid expensive calls
+except Exception:
+    _package_map = None
 
 logger = logging.get_logger(__name__)  # pylint: disable=invalid-name
 
@@ -56,15 +59,13 @@ _is_google_colab = "google.colab" in sys.modules or any(k.startswith("COLAB_") f
 
 
 def _is_package_available(pkg_name: str, get_dist_name: bool = False) -> Tuple[bool, str]:
+    global _package_map
     pkg_exists = importlib.util.find_spec(pkg_name) is not None
     pkg_version = "N/A"
 
     if pkg_exists:
-        try:
-            package_map = importlib_metadata.packages_distributions()
-        except Exception as e:
-            package_map = defaultdict(list)
-            if isinstance(e, AttributeError):
+        if _package_map is None:
+            _package_map = defaultdict(list)
             try:
                 # Fallback for Python < 3.10
                 for dist in importlib_metadata.distributions():
@@ -74,17 +75,16 @@ def _is_package_available(pkg_name: str, get_dist_name: bool = False) -> Tuple[b
                     } - {None}
                     _top_level_inferred = filter(lambda name: "." not in name, _infered_opt_names)
                     for pkg in _top_level_declared or _top_level_inferred:
-                            package_map[pkg].append(dist.metadata["Name"])
+                        _package_map[pkg].append(dist.metadata["Name"])
             except Exception as _:
                 pass
-
         try:
-            if get_dist_name and pkg_name in package_map and package_map[pkg_name]:
-                if len(package_map[pkg_name]) > 1:
+            if get_dist_name and pkg_name in _package_map and _package_map[pkg_name]:
+                if len(_package_map[pkg_name]) > 1:
                     logger.warning(
-                        f"Multiple distributions found for package {pkg_name}. Picked distribution: {package_map[pkg_name][0]}"
+                        f"Multiple distributions found for package {pkg_name}. Picked distribution: {_package_map[pkg_name][0]}"
                     )
-                pkg_name = package_map[pkg_name][0]
+                pkg_name = _package_map[pkg_name][0]
             pkg_version = importlib_metadata.version(pkg_name)
             logger.debug(f"Successfully imported {pkg_name} version {pkg_version}")
         except (ImportError, importlib_metadata.PackageNotFoundError):