Unify {to/from}_pkg_info with {to/from}_dist_info_metadata

As discussed in #383 instead of having 2 separated sets of methods
(one for `PKG-INFO` files in sdists and one for `METADATA` files in wheels)
we can have a single pair to/from functions with an
`allow_unfilled_dynamic` keyword argument.

packaging/metadata.py

@@ -200,28 +200,21 @@ def _parse_pkg_info(cls, pkg_info: bytes) -> Iterable[Tuple[str, Any]]:
             yield ("description", str(info.get_payload(decode=True), "utf-8"))
 
     @classmethod
-    def from_pkg_info(cls: Type[T], pkg_info: bytes) -> T:
+    def from_pkg_info(
+        cls: Type[T], pkg_info: bytes, *, allow_unfilled_dynamic: bool = True
+    ) -> T:
         """Parse PKG-INFO data."""
 
         attrs = cls._process_attrs(cls._parse_pkg_info(pkg_info))
         obj = cls(**dict(attrs))
-        obj._validate_required_fields()
-        obj._validate_dynamic()
-        return obj
-
-    @classmethod
-    def from_dist_info_metadata(cls: Type[T], metadata_source: bytes) -> T:
-        """Parse METADATA data."""
+        obj._validate(allow_unfilled_dynamic)
 
-        obj = cls.from_pkg_info(metadata_source)
-        obj._validate_final_metadata()
         return obj
 
-    def to_pkg_info(self) -> bytes:
+    def to_pkg_info(self, *, allow_unfilled_dynamic: bool = True) -> bytes:
         """Generate PKG-INFO data."""
 
-        self._validate_required_fields()
-        self._validate_dynamic()
+        self._validate(allow_unfilled_dynamic)
 
         info = EmailMessage(self._PARSING_POLICY)
         info.add_header("Metadata-Version", self.metadata_version)
@@ -251,12 +244,6 @@ def to_pkg_info(self) -> bytes:
 
         return info.as_bytes()
 
-    def to_dist_info_metadata(self) -> bytes:
-        """Generate METADATA data."""
-
-        self._validate_final_metadata()
-        return self.to_pkg_info()
-
     # --- Auxiliary Methods and Properties ---
     # Not part of the API, but can be overwritten by subclasses
     # (useful when providing a prof-of-concept for new PEPs)
@@ -343,16 +330,25 @@ def _unescape_description(cls, content: str) -> str:
         continuation = (line.lstrip("|") for line in lines[1:])
         return "\n".join(chain(lines[:1], continuation))
 
+    def _validate(self, allow_unfilled_dynamic: bool) -> bool:
+        self._validate_required_fields()
+        self._validate_dynamic()
+        if not allow_unfilled_dynamic:
+            self._validate_unfilled_dynamic()
+
+        return True
+
     def _validate_dynamic(self) -> bool:
         for item in self.dynamic:
             field = _field_name(item)
             if not hasattr(self, field):
                 raise InvalidCoreMetadataField(item)
             if field in self._NOT_DYNAMIC:
                 raise InvalidDynamicField(item)
+
         return True
 
-    def _validate_final_metadata(self) -> bool:
+    def _validate_unfilled_dynamic(self) -> bool:
         unresolved = [k for k in self.dynamic if not getattr(self, _field_name(k))]
         if unresolved:
             raise UnfilledDynamicFields(unresolved)

tests/test_metadata.py

@@ -6,6 +6,7 @@
 import json
 import tarfile
 from email.policy import compat32
+from functools import partial
 from hashlib import md5
 from itertools import chain
 from pathlib import Path
@@ -207,11 +208,11 @@ def test_parsing(self, spec: str) -> None:
         text = bytes(dedent(example["file_contents"]), "UTF-8")
         pkg_info = CoreMetadata.from_pkg_info(text)
         if example["is_final_metadata"]:
-            metadata = CoreMetadata.from_dist_info_metadata(text)
+            metadata = CoreMetadata.from_pkg_info(text, allow_unfilled_dynamic=False)
             assert_equal_metadata(metadata, pkg_info)
         if example["has_dynamic_fields"]:
             with pytest.raises(UnfilledDynamicFields):
-                CoreMetadata.from_dist_info_metadata(text)
+                CoreMetadata.from_pkg_info(text, allow_unfilled_dynamic=False)
         for field in ("requires_dist", "provides_dist", "obsoletes_dist"):
             for value in getattr(pkg_info, field):
                 assert isinstance(value, Requirement)
@@ -225,10 +226,10 @@ def test_serliazing(self, spec: str) -> None:
         text = bytes(dedent(example["file_contents"]), "UTF-8")
         pkg_info = CoreMetadata.from_pkg_info(text)
         if example["is_final_metadata"]:
-            assert isinstance(pkg_info.to_dist_info_metadata(), bytes)
+            assert isinstance(pkg_info.to_pkg_info(allow_unfilled_dynamic=False), bytes)
         if example["has_dynamic_fields"]:
             with pytest.raises(UnfilledDynamicFields):
-                pkg_info.to_dist_info_metadata()
+                pkg_info.to_pkg_info(allow_unfilled_dynamic=False)
         pkg_info_text = pkg_info.to_pkg_info()
         assert isinstance(pkg_info_text, bytes)
         # Make sure generated document is not empty
@@ -274,14 +275,14 @@ class TestIntegration:
     @pytest.mark.parametrize("pkg, version", examples())
     def test_parse(self, pkg: str, version: str) -> None:
         for dist in download_dists(pkg, version):
+            from_ = CoreMetadata.from_pkg_info
+            to_ = CoreMetadata.to_pkg_info
             if dist.suffix == ".whl":
                 orig = read_metadata(dist)
-                from_ = CoreMetadata.from_dist_info_metadata
-                to_ = CoreMetadata.to_dist_info_metadata
+                from_ = partial(from_, allow_unfilled_dynamic=False)
+                to_ = partial(to_, allow_unfilled_dynamic=False)
             else:
                 orig = read_pkg_info(dist)
-                from_ = CoreMetadata.from_pkg_info
-                to_ = CoreMetadata.to_pkg_info
 
             # Given PKG-INFO or METADATA from existing packages on PyPI
             # - Make sure they can be parsed