revert: remove attribute locking

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

README.md

@@ -49,13 +49,6 @@ A backend is also expected to copy entries from `project.licence_files`, which
 are paths relative to the project directory, into the `dist-info/licenses`
 folder, preserving the original source structure.
 
-## Modifying metadata
-
-By default, `StandardMetadata` metadata fields are immutable unless a field is
-listed in `dynaimc` (not to be confused with `dynamic_metadata`). If you want to
-modify fields that are not dynamic, you can use the `dataclasses.replace` /
-`copy.replace` (Python 3.13+) function.
-
 ## Dynamic Metadata (METADATA 2.2+)
 
 Pyproject-metadata supports dynamic metadata. To use it, specify your METADATA

pyproject_metadata/__init__.py

@@ -126,7 +126,6 @@ class _SmartMessageSetter:
     reduce boilerplate.
 
     If a value is None, do nothing.
-    If a value contains a newline, indent it (may produce a warning in the future).
     """
 
     message: email.message.Message
@@ -252,23 +251,10 @@ class StandardMetadata:
     """
     If True, all errors will be collected and raised in an ExceptionGroup.
     """
-    _locked_metadata: bool = False
-    """
-    Internal flag to prevent setting non-dynamic fields after initialization.
-    """
 
     def __post_init__(self) -> None:
         self.validate()
 
-    def __setattr__(self, name: str, value: Any) -> None:
-        if self._locked_metadata:
-            metadata_name = name.replace("_", "-")
-            locked_fields = constants.KNOWN_METADATA_FIELDS - set(self.dynamic)
-            if metadata_name in locked_fields:
-                msg = f"Field {name!r} is not dynamic"
-                raise AttributeError(msg)
-        super().__setattr__(name, value)
-
     @property
     def auto_metadata_version(self) -> str:
         """
@@ -442,7 +428,6 @@ def from_pyproject(  # noqa: C901
                 metadata_version=metadata_version,
                 all_errors=all_errors,
             )
-            self._locked_metadata = True
 
         pyproject.finalize("Failed to parse pyproject.toml")
         assert self is not None

tests/test_standard_metadata.py

@@ -1488,10 +1488,7 @@ def test_modify_dynamic() -> None:
         }
     )
     metadata.requires_python = packaging.specifiers.SpecifierSet(">=3.12")
-    with pytest.raises(
-        AttributeError, match=re.escape("Field 'version' is not dynamic")
-    ):
-        metadata.version = packaging.version.Version("1.2.3")
+    metadata.version = packaging.version.Version("1.2.3")
 
 
 def test_missing_keys_warns() -> None: