Move optional import stuff out to a separate module to avoid circular imports

Author: charles-turner-1

intake_esm/__init__.py

@@ -11,25 +11,12 @@
 from intake_esm.core import esm_datastore
 from intake_esm.derived import DerivedVariableRegistry, default_registry
 from intake_esm.utils import set_options, show_versions
+from intake_esm._imports import _to_opt_import_flag, _from_opt_import_flag
+from intake_esm import _imports as _import_module
 
 from intake_esm._version import __version__
 
-_optional_imports: dict[str, bool | None] = {'esmvalcore': None}
-
-
-def _to_opt_import_flag(name: str) -> str:
-    """Dynamically create import flags for optional imports."""
-    return f'_{name.upper()}_AVAILABLE'
-
-
-def _from_opt_import_flag(name: str) -> str:
-    """Dynamically retrive the optional import name from its flag."""
-    if name.startswith('_') and name.endswith('_AVAILABLE'):
-        return name[1:-10].lower()
-    raise ValueError(
-        f"Invalid optional import flag '{name}'. Expected format: '_<import_name>_AVAILABLE'."
-    )
-
+import_flags = [_to_opt_import_flag(name) for name in _import_module._optional_imports]
 
 __all__ = [
     'esm_datastore',
@@ -38,7 +25,8 @@ def _from_opt_import_flag(name: str) -> str:
     'set_options',
     'show_versions',
     'tutorial',
-] + [_to_opt_import_flag(name) for name in _optional_imports]
+    '__version__',
+] + import_flags
 
 
 def __getattr__(attr: str) -> object:
@@ -49,17 +37,10 @@ def __getattr__(attr: str) -> object:
     if attr in (gl := globals()):
         return gl[attr]
 
-    import_flags = [_to_opt_import_flag(name) for name in _optional_imports]
-
-    if attr in import_flags:
-        import_name = _from_opt_import_flag(attr)
-        if _optional_imports.get(import_name, None) is None:
-            _optional_imports[import_name] = bool(importlib.util.find_spec(import_name))
-            return _optional_imports[import_name]
-        else:
-            return _optional_imports[import_name]
-
-    raise AttributeError(
-        f"Module '{__name__}' has no attribute '{attr}'. "
-        f'Did you mean one of {", ".join(import_flags)}?'
-    )
+    try:
+        return getattr(_import_module, attr)
+    except AttributeError:
+        raise AttributeError(
+            f"Module '{__name__}' has no attribute '{attr}'. "
+            f'Did you mean one of {", ".join(import_flags)}?'
+        )

intake_esm/_imports.py

@@ -0,0 +1,41 @@
+import importlib
+
+_optional_imports: dict[str, bool | None] = {'esmvalcore': None}
+
+
+def _to_opt_import_flag(name: str) -> str:
+    """Dynamically create import flags for optional imports."""
+    return f'_{name.upper()}_AVAILABLE'
+
+
+def _from_opt_import_flag(name: str) -> str:
+    """Dynamically retrive the optional import name from its flag."""
+    if name.startswith('_') and name.endswith('_AVAILABLE'):
+        return name[1:-10].lower()
+    raise ValueError(
+        f"Invalid optional import flag '{name}'. Expected format: '_<import_name>_AVAILABLE'."
+    )
+
+
+def __getattr__(attr: str) -> object:
+    """
+    Lazy load optional imports.
+    """
+
+    if attr in (gl := globals()):
+        return gl[attr]
+
+    import_flags = [_to_opt_import_flag(name) for name in _optional_imports]
+
+    if attr in import_flags:
+        import_name = _from_opt_import_flag(attr)
+        if _optional_imports.get(import_name, None) is None:
+            _optional_imports[import_name] = bool(importlib.util.find_spec(import_name))
+            return _optional_imports[import_name]
+        else:
+            return _optional_imports[import_name]
+
+    raise AttributeError(
+        f"Module '{__name__}' has no attribute '{attr}'. "
+        f'Did you mean one of {", ".join(import_flags)}?'
+    )

tests/conftest.py

@@ -21,8 +21,8 @@ def sample_bad_input():
 def cleanup_init():
     """
     This resets the _optional_imports dictionary in intake_esm to it's default
-    state, so we can test lazy loading and whatnot
+    state before & after tests that use it  so we can test lazy loading and whatnot
     """
+    intake_esm._imports._optional_imports = {'esmvalcore': None}
     yield
-
-    intake_esm._optional_imports = {'esmvalcore': None}
+    intake_esm._imports._optional_imports = {'esmvalcore': None}

tests/test_init.py

@@ -13,6 +13,7 @@ def test__all__(cleanup_init):
         'set_options',
         'show_versions',
         'tutorial',
+        '__version__',
         '_ESMVALCORE_AVAILABLE',
     ]