fix(typing): Relax dict annotations in channels.py (#3573)

tests/vegalite/v5/test_api.py

@@ -644,6 +644,24 @@ def test_when_multiple_fields():
         )
 
 
+def test_when_typing(cars) -> None:
+    color = (
+        alt.when(alt.datum.Weight_in_lbs >= 3500)
+        .then(alt.value("black"))
+        .otherwise(alt.value("white"))
+    )
+    source = cars
+    chart = (  # noqa: F841
+        alt.Chart(source)
+        .mark_rect()
+        .encode(
+            x=alt.X("Cylinders:N").axis(labelColor=color),
+            y=alt.Y("Origin:N", axis=alt.Axis(tickColor=color)),
+            color=color,
+        )
+    )
+
+
 @pytest.mark.parametrize(
     ("channel", "then", "otherwise"),
     [

tools/generate_schema_wrapper.py

@@ -819,6 +819,8 @@ def vegalite_main(skip_download: bool = False) -> None:
     ]
     ruff_write_lint_format_str(outfile, content)
 
+    TypeAliasTracer.update_aliases(("Map", "Mapping[str, Any]"))
+
     files: dict[Path, str | Iterable[str]] = {}
 
     # Generate the core schema wrappers
@@ -871,7 +873,6 @@ def vegalite_main(skip_download: bool = False) -> None:
         f"Tracer cache collected {TypeAliasTracer.n_entries!r} entries."
     )
     print(msg)
-    TypeAliasTracer.update_aliases(("Map", "Mapping[str, Any]"))
     TypeAliasTracer.write_module(
         fp_typing, "OneOrSeq", header=HEADER, extra=TYPING_EXTRA
     )

tools/schemapi/utils.py

@@ -38,7 +38,7 @@
     "string": "str",
     "number": "float",
     "integer": "int",
-    "object": "dict",
+    "object": "Map",
     "boolean": "bool",
     "array": "list",
     "null": "None",
@@ -159,7 +159,7 @@ def is_cached(self, tp: str, /) -> bool:
 
         Currently used as a sort key, to place literals/aliases last.
         """
-        return tp in self._literals_invert or tp in self._literals
+        return tp in self._literals_invert or tp in self._literals or tp in self._aliases  # fmt: skip
 
     def write_module(
         self, fp: Path, *extra_all: str, header: LiteralString, extra: LiteralString
@@ -449,7 +449,7 @@ def get_python_type_representation(  # noqa: C901
                     )
                 )
             type_representations.extend(options)
-        elif self.is_object():
+        elif self.is_object() and not for_type_hints:
             type_representations.append("dict")
         elif self.is_array():
             # A list is invariant in its type parameter. This means that e.g.