core.common: move away import related stuff to my.core.utils.imports

moving without backward compatibility, since it's extremely unlikely they are used for any external modules

in fact, unclear if these methods still have much value at all, but keeping for now just in case

my/core/utils/imports.py

@@ -0,0 +1,37 @@
+import importlib
+import importlib.util
+from pathlib import Path
+import sys
+from typing import Optional
+from types import ModuleType
+
+from ..common import PathIsh
+
+
+# TODO only used in tests? not sure if useful at all.
+def import_file(p: PathIsh, name: Optional[str] = None) -> ModuleType:
+    p = Path(p)
+    if name is None:
+        name = p.stem
+    spec = importlib.util.spec_from_file_location(name, p)
+    assert spec is not None, f"Fatal error; Could not create module spec from {name} {p}"
+    foo = importlib.util.module_from_spec(spec)
+    loader = spec.loader; assert loader is not None
+    loader.exec_module(foo)
+    return foo
+
+
+def import_from(path: PathIsh, name: str) -> ModuleType:
+    path = str(path)
+    sys.path.append(path)
+    try:
+        return importlib.import_module(name)
+    finally:
+        sys.path.remove(path)
+
+
+def import_dir(path: PathIsh, extra: str = '') -> ModuleType:
+    p = Path(path)
+    if p.parts[0] == '~':
+        p = p.expanduser()  # TODO eh. not sure about this..
+    return import_from(p.parent, p.name + extra)

my/core/utils/itertools.py

@@ -105,12 +105,13 @@ else:
 
 
 def test_listify() -> None:
+    from ..compat import assert_type
+
     @listify
     def it() -> Iterator[int]:
         yield 1
         yield 2
 
     res = it()
-    from typing_extensions import assert_type  # TODO move to compat?
     assert_type(res, List[int])
     assert res == [1, 2]