feat(typing): Properly annotate dataset_name, suffix

Makes more sense following (755ab4f)

altair/datasets/_typing.py

@@ -11,6 +11,11 @@
 else:
     from typing_extensions import TypedDict
 
+if sys.version_info >= (3, 11):
+    from typing import LiteralString
+else:
+    from typing_extensions import LiteralString
+
 if sys.version_info >= (3, 10):
     from typing import TypeAlias
 else:
@@ -181,8 +186,8 @@ class Metadata(TypedDict, total=False):
     ```
     """
 
-    dataset_name: str
-    suffix: str
+    dataset_name: Dataset | LiteralString
+    suffix: Extension
     file_name: str
     bytes: int
     is_image: bool

tools/datasets/__init__.py

@@ -184,6 +184,7 @@ def generate_typing(self, dpkg: datapackage.DataPackage) -> None:
             "import sys",
             "from typing import Literal, TYPE_CHECKING",
             utils.import_typing_extensions((3, 14), "TypedDict"),
+            utils.import_typing_extensions((3, 11), "LiteralString"),
             utils.import_typing_extensions((3, 10), "TypeAlias"),
             "\n",
             f"__all__ = {[NAME, EXT, dpkg._NAME_TYPED_DICT]}\n",

tools/datasets/datapackage.py

@@ -31,10 +31,13 @@
 
 
 class Column:
-    def __init__(self, name: str, expr: pl.Expr, /, doc: str = "_description_") -> None:
+    def __init__(
+        self, name: str, expr: pl.Expr, /, doc: str = "_description_", tp_str: str = ""
+    ) -> None:
         self._name: str = name
         self._expr: pl.Expr = expr
         self._doc: str = doc
+        self._tp_str: str = tp_str
 
     @property
     def expr(self) -> pl.Expr:
@@ -161,7 +164,10 @@ def _metadata_examples(self) -> str:
     @property
     def _metadata_td_args(self) -> str:
         schema = self.core.collect_schema().to_python()
-        return f"\n{INDENT}".join(f"{p}: {tp.__name__}" for p, tp in schema.items())
+        return f"\n{INDENT}".join(
+            f"{column._name}: {column._tp_str or tp.__name__}"
+            for column, tp in zip(self.columns, schema.values())
+        )
 
     @property
     def _url(self) -> Column:
@@ -237,8 +243,18 @@ def note(s: str, /) -> str:
 
 fmt = col("format")
 DataPackage.with_columns(
-    Column("dataset_name", path_stem("path"), "Name of the dataset/`Path.stem`_."),
-    Column("suffix", path_suffix("path"), "File extension/`Path.suffix`_."),
+    Column(
+        "dataset_name",
+        path_stem("path"),
+        "Name of the dataset/`Path.stem`_.",
+        tp_str="Dataset | LiteralString",
+    ),
+    Column(
+        "suffix",
+        path_suffix("path"),
+        "File extension/`Path.suffix`_.",
+        tp_str="Extension",
+    ),
     Column("file_name", col("path"), "Equivalent to `Path.name`_."),
     Column("bytes", col("bytes"), "File size in *bytes*."),
     Column("is_image", fmt == "png", "Only accessible via url."),