Correct missing arguments message in presence of kwargs unpacking

Author: sterliakov

mypy/checkexpr.py

@@ -2389,14 +2389,22 @@ def check_argument_count(
         )
 
         # Check for too many or few values for formals.
+        missing_contiguous_pos_block = []
+        seen_kw = False
         for i, kind in enumerate(callee.arg_kinds):
             mapped_args = formal_to_actual[i]
+            seen_kw = seen_kw or any(actual_kinds[k].is_named(star=True) for k in mapped_args)
             if kind.is_required() and not mapped_args and not is_unexpected_arg_error:
                 # No actual for a mandatory formal
-                if kind.is_positional():
-                    self.msg.too_few_arguments(callee, context, actual_names)
-                    if object_type and callable_name and "." in callable_name:
-                        self.missing_classvar_callable_note(object_type, callable_name, context)
+                if (
+                    kind.is_positional()
+                    and not seen_kw
+                    and (
+                        not missing_contiguous_pos_block
+                        or missing_contiguous_pos_block[-1] == i - 1
+                    )
+                ):
+                    missing_contiguous_pos_block.append(i)
                 else:
                     argname = callee.arg_names[i] or "?"
                     self.msg.missing_named_argument(callee, context, argname)
@@ -2432,6 +2440,22 @@ def check_argument_count(
                     if actual_kinds[mapped_args[0]] == nodes.ARG_STAR2 and paramspec_entries > 1:
                         self.msg.fail("ParamSpec.kwargs should only be passed once", context)
                         ok = False
+        if missing_contiguous_pos_block:
+            if ArgKind.ARG_STAR2 in actual_kinds:
+                # To generate a correct message, expand kwargs manually. If a name was
+                # missing from the call but doesn't belong to continuous positional prefix,
+                # it was already reported as a missing kwarg. All args before first prefix
+                # item are guaranteed to have been passed positionally.
+                names_to_use = [None] * missing_contiguous_pos_block[0] + [
+                    name
+                    for i, name in enumerate(callee.arg_names)
+                    if name is not None and i not in missing_contiguous_pos_block
+                ]
+            else:
+                names_to_use = actual_names
+            self.msg.too_few_arguments(callee, context, names_to_use)
+            if object_type and callable_name and "." in callable_name:
+                self.missing_classvar_callable_note(object_type, callable_name, context)
         return ok
 
     def check_for_extra_actual_arguments(

test-data/unit/check-functions.test

@@ -2467,6 +2467,79 @@ f(b=4) # E: Missing positional argument "a" in call to "f"
 def f(a, b, c, d=None) -> None: pass
 f(1, d=3) # E: Missing positional arguments "b", "c" in call to "f"
 
+[case testMissingArgumentsErrorFromTypedDict]
+from typing import Optional,TypedDict
+
+class DA(TypedDict):
+    a: int
+class DB(TypedDict):
+    b: int
+class DC(TypedDict):
+    c: int
+
+class DAB(DA, DB): pass
+class DAC(DA, DC): pass
+class DBC(DB, DC): pass
+class DABC(DA, DB, DC): pass
+
+da: DA
+db: DB
+dc: DC
+dab: DAB
+dac: DAC
+dbc: DBC
+dabc: DABC
+
+def f(a: int, b: int, c: int, d: Optional[int] = None) -> None: pass
+
+f(**da)  # E: Missing named argument "b" for "f" \
+         # E: Missing named argument "c" for "f"
+f(**db)  # E: Missing named argument "c" for "f" \
+         # E: Missing positional argument "a" in call to "f"
+f(**dc)  # E: Missing positional arguments "a", "b" in call to "f"
+f(**dab)  # E: Missing named argument "c" for "f"
+f(**dac)  # E: Missing named argument "b" for "f"
+f(**dbc)  # E: Missing positional argument "a" in call to "f"
+f(**dabc)
+
+def g(a: int, /, b: int, c: int) -> None: pass
+
+g(**da)  # E: Extra argument "a" from **args for "g"
+g(0, **da)  # E: Extra argument "a" from **args for "g"
+g(**db)  # E: Missing named argument "c" for "g" \
+         # E: Too few arguments for "g"
+g(0, **db)  # E: Missing named argument "c" for "g"
+g(**dc)  # E: Too few arguments for "g"
+g(0, **dc)  # E: Missing positional argument "b" in call to "g"
+g(**dab)  # E: Extra argument "a" from **args for "g"
+g(0, **dab)  # E: Extra argument "a" from **args for "g"
+g(**dac)  # E: Extra argument "a" from **args for "g"
+g(0, **dac)  # E: Extra argument "a" from **args for "g"
+g(**dbc)  # E: Too few arguments for "g"
+g(0, **dbc)
+g(**dabc)  # E: Extra argument "a" from **args for "g"
+
+def h(a: int, b: int, /, c: int) -> None: pass
+
+h(**da)  # E: Extra argument "a" from **args for "h"
+h(0, **da)  # E: Extra argument "a" from **args for "h"
+h(0, 1, **da)  # E: Extra argument "a" from **args for "h"
+h(**db)  # E: Extra argument "b" from **args for "h"
+h(0, **db)  # E: Extra argument "b" from **args for "h"
+h(0, 1, **db)  # E: Extra argument "b" from **args for "h"
+h(**dc)  # E: Too few arguments for "h"
+h(0, **dc)  # E: Too few arguments for "h"
+h(0, 1, **dc)
+h(**dab)  # E: Extra argument "b" from **args for "h"
+h(0, **dab)  # E: Extra argument "b" from **args for "h"
+h(**dac)  # E: Extra argument "a" from **args for "h"
+h(0, **dac)  # E: Extra argument "a" from **args for "h"
+h(**dbc)  # E: Extra argument "b" from **args for "h"
+h(0, **dbc)  # E: Extra argument "b" from **args for "h"
+h(**dabc)  # E: Extra argument "b" from **args for "h"
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]
+
 [case testReturnTypeLineNumberWithDecorator]
 def dec(f): pass