Add is_iterable and use in test_asset_check_decorator

python_modules/dagster/dagster/_check/__init__.py

@@ -1233,6 +1233,34 @@ def opt_nullable_iterable_param(
     return iterable_param(obj, param_name, of_type, additional_message)
 
 
+def old_is_iterable(
+    obj: object,
+    of_type: Optional[TypeOrTupleOfTypes] = None,
+    additional_message: Optional[str] = None,
+) -> Iterable:
+    if not isinstance(obj, Iterable):
+        raise _type_mismatch_error(obj, list, additional_message)
+
+    if not of_type:
+        return obj
+
+    return _check_iterable_items(obj, of_type, "list")
+
+
+def is_iterable(
+    obj: object,
+    of_type: Optional[TTypeOrTupleOfTTypes[T]] = None,
+    additional_message: Optional[str] = None,
+) -> Iterable[T]:
+    if not isinstance(obj, Iterable):
+        raise _type_mismatch_error(obj, list, additional_message)
+
+    if not of_type:
+        return obj
+
+    return _check_iterable_items(obj, of_type, "list")
+
+
 # ########################
 # ##### SET
 # ########################

python_modules/dagster/dagster_tests/definitions_tests/decorators_tests/test_asset_check_decorator.py

@@ -848,9 +848,7 @@ def checks() -> Iterable[AssetCheckResult]:
         yield AssetCheckResult(passed=False, asset_key="asset1", check_name="check2")
         yield AssetCheckResult(passed=True, asset_key="asset2")
 
-    checks_ret_obj = checks()
-    assert isinstance(checks_ret_obj, Iterable)
-    results = check.is_list(list(checks_ret_obj), of_type=AssetCheckResult)
+    results = check.is_list(check.is_iterable(checks()), of_type=AssetCheckResult)
     assert len(results) == 3
     assert all(isinstance(result, AssetCheckResult) for result in results)
     assert results[0].passed

python_modules/dagster/dagster_tests/general_tests/check_tests/test_check.py

@@ -3,7 +3,7 @@
 import sys
 from collections import defaultdict
 from contextlib import contextmanager
-from typing import Dict, Iterable, List, Mapping, Optional, Sequence, Set, Union
+from typing import Any, Dict, Iterable, List, Mapping, Optional, Sequence, Set, Union
 
 import dagster._check as check
 import pytest
@@ -1514,6 +1514,42 @@ def test_opt_iterable():
         check.opt_iterable_param(["atr", None], "nonedoesntcount", of_type=str)
 
 
+def test_is_iterable() -> None:
+    assert check.is_iterable([]) == []
+    assert check.is_iterable((1, 2)) == tuple([1, 2])
+    assert check.is_iterable("foo") == "foo"  # str is iterable
+    assert check.is_iterable({"a": 1}) == {"a": 1}  # dict is iterable
+
+    assert check.is_iterable([1, "str"]) == [1, "str"]
+
+    with pytest.raises(CheckError):
+        check.is_iterable([1, "str"], of_type=int)
+
+    with pytest.raises(CheckError):
+        check.is_iterable([1, "str"], of_type=str)
+
+    with pytest.raises(CheckError):
+        check.is_iterable(None)
+
+    with pytest.raises(CheckError):
+        check.is_iterable(1)
+
+
+def test_is_iterable_typing() -> None:
+    def returns_iterable_of_int_but_typed_any() -> Any:
+        return [1, 2]
+
+    def returns_iterable_of_t() -> Iterable[int]:
+        any_typed = returns_iterable_of_int_but_typed_any()
+        retval = check.is_iterable(any_typed, of_type=str)
+        # That the type: ignore is necessary is proof that
+        # is_iterable flows type information correctly
+        return retval  # type: ignore
+
+    # meaningless assert. The test is show the typechecker working
+    assert returns_iterable_of_t
+
+
 # ###################################################################################################
 # ##### CHECK BUILDER
 # ###################################################################################################