wip

learn_sql_model/optional.py

@@ -0,0 +1,63 @@
+import textwrap
+
+
+def _optional_import_(
+    module: str,
+    name: str = None,
+    group: str = None,
+    package="learn_sql_model",
+):
+    """
+    lazily throws import errors only then the optional import is used, and
+    includes a group install command for the user to install all dependencies
+    for the requested feature.
+    """
+    import importlib
+
+    try:
+        module = importlib.import_module(module)
+        return module if name is None else getattr(module, name)
+    except ImportError as e:
+        msg = textwrap.dedent(
+            f"""
+        "pip install '{package}[{group}]'" package to make use of this feature
+        Alternatively "pip install '{package}[all]'" package to install all optional dependencies
+        """
+        )
+        import_error = e
+
+        class _failed_import:
+            """
+            Lazily throw an import error.  Errors should be thrown whether the
+            user tries to call the module, get an attubute from the module, or
+            getitem from the module.
+
+            """
+
+            def _failed_import(self, *args):
+                raise ImportError(msg) from import_error
+
+            def __call__(self, *args):
+                """
+                Throw error if the user tries to call the module i.e
+                _optional_import_('dummy')()
+                """
+                self._failed_import(*args)
+
+            def __getattr__(self, name):
+                """
+                Throw error if the user tries to get an attribute from the
+                module i.e _optional_import_('dummy').dummy.
+                """
+                if name == "_failed_import":
+                    return object.__getattribute__(self, name)
+                self._failed_import()
+
+            def __getitem__(self, name):
+                """
+                Throw error if the user tries to get an item from the module
+                i.e _optional_import_('dummy')['dummy']
+                """
+                self._failed_import()
+
+        return _failed_import()