fix: ensure needs always works

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

src/scikit_build_core/builder/_load_provider.py

@@ -10,6 +10,8 @@
 if TYPE_CHECKING:
     from collections.abc import Generator, Iterable, Mapping
 
+from ..metadata import _ALL_FIELDS
+
 __all__ = ["load_dynamic_metadata", "load_provider"]
 
 
@@ -80,6 +82,9 @@ def _load_dynamic_metadata(
 ]:
     for field, orig_config in metadata.items():
         if "provider" in orig_config:
+            if field not in _ALL_FIELDS:
+                msg = f"{field} is not a valid field"
+                raise KeyError(msg)
             config = dict(orig_config)
             provider = config.pop("provider")
             provider_path = config.pop("provider-path", None)
@@ -89,6 +94,9 @@ def _load_dynamic_metadata(
                 if isinstance(loaded_provider, DynamicMetadataNeeds)
                 else []
             )
+            if needs > _ALL_FIELDS:
+                msg = f"Invalid dyanmic_metada_needs: {needs - _ALL_FIELDS}"
+                raise KeyError(msg)
             yield field, loaded_provider, config, needs
         else:
             yield field, None, dict(orig_config), frozenset()
@@ -98,6 +106,10 @@ def load_dynamic_metadata(
     metadata: Mapping[str, Mapping[str, str]],
 ) -> list[tuple[str, DMProtocols | None, dict[str, str]]]:
     initial = {f: (p, c, n) for (f, p, c, n) in _load_dynamic_metadata(metadata)}
-    sorter = TopologicalSorter({f: n for f, (_, _, n) in initial.items()})
+
+    dynamic_fields = initial.keys()
+    sorter = TopologicalSorter(
+        {f: n & dynamic_fields for f, (_, _, n) in initial.items()}
+    )
     order = sorter.static_order()
     return [(f, *initial[f][:2]) for f in order]

src/scikit_build_core/metadata/__init__.py

@@ -6,7 +6,7 @@
     from collections.abc import Callable
 
 
-__all__: list[str] = ["_process_dynamic_metadata"]
+__all__: list[str] = ["_ALL_FIELDS", "_process_dynamic_metadata"]
 
 
 # Name is not dynamically settable, so not in this list
@@ -29,6 +29,27 @@
     ]
 )
 
+_DICT_STR_FIELDS = frozenset(
+    [
+        "urls",
+        "authors",
+        "maintainers",
+    ]
+)
+
+# "dynamic" and "name" can't be set or requested
+_ALL_FIELDS = (
+    _STR_FIELDS
+    | _LIST_STR_FIELDS
+    | _DICT_STR_FIELDS
+    | frozenset(
+        [
+            "optional-dependencies",
+            "readme",
+        ]
+    )
+)
+
 T = typing.TypeVar("T", bound="str | list[str] | dict[str, str] | dict[str, list[str]]")
 
 
@@ -47,11 +68,11 @@ def _process_dynamic_metadata(field: str, action: Callable[[str], str], result:
             msg = f"Field {field!r} must be a list of strings"
             raise RuntimeError(msg)
         return [action(r) for r in result]  # type: ignore[return-value]
-    if field == "urls":
+    if field in _DICT_STR_FIELDS:
         if not isinstance(result, dict) or not all(
             isinstance(v, str) for v in result.values()
         ):
-            msg = "Field 'urls' must be a dictionary of strings"
+            msg = f"Field {field!r} must be a dictionary of strings"
             raise RuntimeError(msg)
         return {k: action(v) for k, v in result.items()}  # type: ignore[return-value]
     if field == "optional-dependencies":