misc: Add load_(classes|class_names|object)()

Add some functions to aid in dynamically loading objects.

Signed-off-by: Jan Lindemann <jan@janware.com>

tools/python/jwutils/misc.py

@@ -3,6 +3,7 @@ import atexit
 import tempfile
 import filecmp
 import inspect
+import importlib
 from typing import Set
 from jwutils import log
 
@@ -50,7 +51,7 @@ def object_builtin_name(o, full=True): # export
         return o.__class__.__name__  # Avoid reporting __builtin__
     return module + '.' + o.__class__.__name__
 
-def get_derived_classes(mod, base): # export
+def get_derived_classes(mod, base, flt=None): # export
     members = inspect.getmembers(mod, inspect.isclass)
     r = []
     for name, c in members:
@@ -61,9 +62,43 @@ def get_derived_classes(mod, base): # export
         if not base in inspect.getmro(c):
             log.slog(log.DEBUG, "  is not derived from", base, "only", inspect.getmro(c))
             continue
+        if flt and not re.match(flt, name):
+            slog(DEBUG, '  "{}.{}" has wrong name'.format(mod, name))
+            continue
         r.append(c)
     return r
 
+def load_classes(path, baseclass, flt=None): # export
+    r = []
+    for p in path.split(':'):
+        mod = importlib.import_module(path)
+        r.extend(get_derived_classes(mod, baseclass, flt))
+    return r
+
+def load_class_names(path, baseclass, flt=None, remove_flt=False): # export
+    classes = load_classes(path, baseclass, flt)
+    r = []
+    for c in classes:
+        name = c.__name__
+        if flt and remove_flt:
+            name = re.subst(flt, "", name)
+        if name not in r:
+            r.append(name)
+        else:
+            pass
+            #log.slog(log.WARNING, "{} is already in in {}".format(name, r))
+    return r
+
+# TODO: handling of "name" / "flt" is awkward
+def load_object(path, baseclass, name = None, *args, **kwargs): # export
+    mod = importlib.import_module(path)
+    classes = get_derived_classes(mod, baseclass, flt=None)
+    if len(classes) == 0:
+        raise Exception("no class {} found".format(name))
+    if len(classes) > 1:
+        raise Exception("{} classes matching {} found".format(len(classes), name))
+    return classes[0](*args, **kwargs)
+
 def commit_tmpfile(tmp: str, path: str) -> None: # export
     caller = log.get_caller_pos()
     if os.path.isfile(path) and filecmp.cmp(tmp, path):