Deprecate iter(dataclass_instance), which was a confusing behavior.

runtype/dataclass.py

@@ -10,6 +10,7 @@
 from abc import ABC, abstractmethod
 import inspect
 import types
+import warnings
 
 if TYPE_CHECKING:
     from typing_extensions import dataclass_transform
@@ -201,14 +202,19 @@ def replace(inst, **kwargs):
 
 def __iter__(inst):
     "Yields a list of tuples [(name, value), ...]"
-    # TODO: deprecate this method
+    warnings.warn("This method is deprecated and will be removed in future versions."
+                  "Please use `.asdict()` or `.asitems()` instead.", DeprecationWarning)
     return ((name, getattr(inst, name)) for name in inst.__dataclass_fields__)
 
 def asdict(inst):
     """Returns a dict of {name: value, ...}
     """
     return {name: getattr(inst, name) for name in inst.__dataclass_fields__}
 
+def asitems(inst):
+    "Yields a list of tuples [(name, value), ...]"
+    return ((name, getattr(inst, name)) for name in inst.__dataclass_fields__)
+
 def aslist(inst):
     """Returns a list of the values
     """
@@ -234,7 +240,7 @@ def json(inst):
     """Returns a JSON of values, going recursively into other objects (if possible)"""
     return {
         k: _json_rec(v)
-        for k, v in inst
+        for k, v in inst.asitems()
     }
 
 def _set_if_not_exists(cls, d):
@@ -317,6 +323,7 @@ def __post_init__(self):
     _set_if_not_exists(c, {
         'replace': replace,
         'asdict': asdict,
+        'asitems': asitems,
         'aslist': aslist,
         'astuple': astuple,
         'json': json,

tests/test_basic.py

@@ -659,10 +659,10 @@ def __post_init__(self):
                 assert self.x != 0
 
         p = Point(2,3)
-        assert dict(p) == {'x':2, 'y':3}
+        assert p.asdict() == {'x':2, 'y':3}
 
         p2 = p.replace(x=30)
-        assert dict(p2) == {'x':30, 'y':3}
+        # assert dict(p2) == {'x':30, 'y':3}
         assert p2.aslist() == [30, 3]
         assert p2.astuple() == (30, 3)