Add magic value REPLACEME (#881)

* Add magic value REPLACEME

* Lint

esphome/helpers.py

@@ -261,3 +261,51 @@ def file_compare(path1, path2):
             if not blob1:
                 # Reached end
                 return True
+
+
+# A dict of types that need to be converted to heaptypes before a class can be added
+# to the object
+_TYPE_OVERLOADS = {
+    int: type('int', (int,), dict()),
+    float: type('float', (float,), dict()),
+    str: type('str', (str,), dict()),
+    dict: type('dict', (str,), dict()),
+    list: type('list', (list,), dict()),
+}
+
+if IS_PY2:
+    _TYPE_OVERLOADS[long] = type('long', (long,), dict())
+    _TYPE_OVERLOADS[unicode] = type('unicode', (unicode,), dict())
+
+# cache created classes here
+_CLASS_LOOKUP = {}
+
+
+def add_class_to_obj(value, cls):
+    """Add a class to a python type.
+
+    This function modifies value so that it has cls as a basetype.
+    The value itself may be modified by this action! You must use the return
+    value of this function however, since some types need to be copied first (heaptypes).
+    """
+    if isinstance(value, cls):
+        # If already is instance, do not add
+        return value
+
+    try:
+        orig_cls = value.__class__
+        key = (orig_cls, cls)
+        new_cls = _CLASS_LOOKUP.get(key)
+        if new_cls is None:
+            new_cls = orig_cls.__class__(orig_cls.__name__, (orig_cls, cls), {})
+            _CLASS_LOOKUP[key] = new_cls
+        value.__class__ = new_cls
+        return value
+    except TypeError:
+        # Non heap type, look in overloads dict
+        for type_, func in _TYPE_OVERLOADS.items():
+            # Use type() here, we only need to trigger if it's the exact type,
+            # as otherwise we don't need to overload the class
+            if type(value) is type_:  # pylint: disable=unidiomatic-typecheck
+                return add_class_to_obj(func(value), cls)
+        raise