added unittests for multi_input_obj coercion

pydra/utils/tests/test_typing.py

@@ -6,7 +6,7 @@
 import tempfile
 import pytest
 from pydra import mark
-from ...engine.specs import File, LazyOutField
+from ...engine.specs import File, LazyOutField, MultiInputObj
 from ..typing import TypeParser
 from pydra import Workflow
 from fileformats.application import Json, Yaml, Xml
@@ -202,7 +202,7 @@ def test_type_check_fail3():
 
 
 def test_type_check_fail4():
-    with pytest.raises(TypeError, match="Cannot coerce <class 'dict'> into"):
+    with pytest.raises(TypeError, match="Cannot coerce .*(d|D)ict.* into"):
         TypeParser(ty.Sequence)(lz(ty.Dict[str, int]))
 
 
@@ -780,3 +780,63 @@ def test_type_is_instance3():
 
 def test_type_is_instance4():
     assert TypeParser.is_instance(Json, type)
+
+
+def test_multi_input_obj_coerce1():
+    assert TypeParser(MultiInputObj[str])("a") == ["a"]
+
+
+def test_multi_input_obj_coerce2():
+    assert TypeParser(MultiInputObj[str])(["a"]) == ["a"]
+
+
+def test_multi_input_obj_coerce3():
+    assert TypeParser(MultiInputObj[ty.List[str]])(["a"]) == [["a"]]
+
+
+def test_multi_input_obj_coerce3a():
+    assert TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])(["a"]) == [["a"]]
+
+
+def test_multi_input_obj_coerce3b():
+    assert TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])([["a"]]) == [["a"]]
+
+
+def test_multi_input_obj_coerce4():
+    assert TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])([1]) == [1]
+
+
+def test_multi_input_obj_coerce4a():
+    with pytest.raises(TypeError):
+        TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])([[1]])
+
+
+def test_multi_input_obj_check_type1():
+    TypeParser(MultiInputObj[str])(lz(str))
+
+
+def test_multi_input_obj_check_type2():
+    TypeParser(MultiInputObj[str])(lz(ty.List[str]))
+
+
+def test_multi_input_obj_check_type3():
+    TypeParser(MultiInputObj[ty.List[str]])(lz(ty.List[str]))
+
+
+def test_multi_input_obj_check_type3a():
+    TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])(lz(ty.List[str]))
+
+
+def test_multi_input_obj_check_type3b():
+    TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])(lz(ty.List[ty.List[str]]))
+
+
+def test_multi_input_obj_check_type4():
+    TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])(lz(ty.List[int]))
+
+
+def test_multi_input_obj_check_type4a():
+    with pytest.raises(TypeError):
+        TypeParser(MultiInputObj[ty.Union[int, ty.List[str]]])(
+            lz(ty.List[ty.List[int]])
+        )

pydra/utils/typing.py

@@ -2,6 +2,7 @@
 import inspect
 from pathlib import Path
 import os
+from copy import copy
 import sys
 import typing as ty
 import logging
@@ -12,6 +13,7 @@
     MultiInputObj,
     MultiOutputObj,
 )
+from ..utils import add_exc_note
 from fileformats import field
 
 try:
@@ -337,18 +339,26 @@ def coerce_obj(obj, type_):
                     f"Cannot coerce {obj!r} into {type_}{msg}{self.label_str}"
                 ) from e
 
-        # Special handling for MultiInputObjects (which are annoying)
-        if isinstance(self.pattern, tuple) and self.pattern[0] == MultiInputObj:
-            try:
-                self.check_coercible(object_, self.pattern[1][0])
-            except TypeError:
-                pass
+        try:
+            return expand_and_coerce(object_, self.pattern)
+        except TypeError as e:
+            # Special handling for MultiInputObjects (which are annoying)
+            if isinstance(self.pattern, tuple) and self.pattern[0] == MultiInputObj:
+                # Attempt to coerce the object into arg type of the MultiInputObj first,
+                # and if that fails, try to coerce it into a list of the arg type
+                inner_type_parser = copy(self)
+                inner_type_parser.pattern = self.pattern[1][0]
+                try:
+                    return [inner_type_parser.coerce(object_)]
+                except TypeError:
+                    add_exc_note(
+                        e,
+                        "Also failed to coerce to the arg-type of the MultiInputObj "
+                        f"({self.pattern[1][0]})",
+                    )
+                    raise e
             else:
-                obj = [object_]
-        else:
-            obj = object_
-
-        return expand_and_coerce(obj, self.pattern)
+                raise e
 
     def check_type(self, type_: ty.Type[ty.Any]):
         """Checks the given type to see whether it matches or is a subtype of the
@@ -485,12 +495,26 @@ def check_sequence(tp_args, pattern_args):
             for arg in tp_args:
                 expand_and_check(arg, pattern_args[0])
 
-        # Special handling for MultiInputObjects (which are annoying)
-        if isinstance(self.pattern, tuple) and self.pattern[0] == MultiInputObj:
-            pattern = (ty.Union, [self.pattern[1][0], (ty.List, self.pattern[1])])
-        else:
-            pattern = self.pattern
-        return expand_and_check(type_, pattern)
+        try:
+            return expand_and_check(type_, self.pattern)
+        except TypeError as e:
+            # Special handling for MultiInputObjects (which are annoying)
+            if isinstance(self.pattern, tuple) and self.pattern[0] == MultiInputObj:
+                # Attempt to coerce the object into arg type of the MultiInputObj first,
+                # and if that fails, try to coerce it into a list of the arg type
+                inner_type_parser = copy(self)
+                inner_type_parser.pattern = self.pattern[1][0]
+                try:
+                    inner_type_parser.check_type(type_)
+                except TypeError:
+                    add_exc_note(
+                        e,
+                        "Also failed to coerce to the arg-type of the MultiInputObj "
+                        f"({self.pattern[1][0]})",
+                    )
+                    raise e
+            else:
+                raise e
 
     def check_coercible(self, source: ty.Any, target: ty.Union[type, ty.Any]):
         """Checks whether the source object is coercible to the target type given the coercion