feat(project_override): add add_dynamic_field to project_override

Allows declaratively adding PEP 621 dynamic fields to pyproject.toml
via package settings YAML, replacing the need for custom prepare_source
plugins for this common operation.

- New `add_dynamic_field` list in `project_override` settings
- Validates entries against PEP 621 allowed field names
- Merges with existing `[project] dynamic` without duplicates

Closes: #934
Co-Authored-By: Claude Code <noreply@anthropic.com>
Signed-off-by: Josef Skladanka <jskladan@redhat.com>

Author: jskladan

docs/customization.md

@@ -373,6 +373,10 @@ Packages are matched by canonical name.
 - `update_build_requires` a list of requirement specifiers. Existing specs
   are replaced and missing specs are added. The option can be used to add,
   remove, or change a version constraint.
+- `add_dynamic_field` is a list of
+  [PEP 621](https://peps.python.org/pep-0621/#dynamic) field names to add
+  to `[project] dynamic`. New entries are merged with any existing dynamic
+  fields without duplicates.
 
 ```yaml
 project_override:
@@ -382,6 +386,9 @@ project_override:
         - setuptools>=68.0.0
         - torch
         - triton
+    add_dynamic_field:
+        - readme
+        - version
 ```
 
 Incoming `pyproject.toml`:
@@ -396,6 +403,9 @@ Output:
 ```yaml
 [build-system]
 requires = ["setuptools>=68.0.0", "torch", "triton"]
+
+[project]
+dynamic = ["readme", "version"]
 ```
 
 ## Override plugins

src/fromager/packagesettings/__init__.py

@@ -2,6 +2,7 @@
 
 from ._hooks import default_update_extra_environ, get_extra_environ
 from ._models import (
+    PEP621_DYNAMIC_FIELDS,
     BuildOptions,
     DownloadSource,
     GitOptions,
@@ -33,6 +34,7 @@
 
 __all__ = (
     "MODEL_CONFIG",
+    "PEP621_DYNAMIC_FIELDS",
     "Annotations",
     "BuildDirectory",
     "BuildOptions",

src/fromager/packagesettings/_models.py

@@ -260,6 +260,27 @@ class BuildOptions(pydantic.BaseModel):
     """If true, this package must be built on its own (not in parallel with other packages). Default: False."""
 
 
+PEP621_DYNAMIC_FIELDS: frozenset[str] = frozenset(
+    {
+        "version",
+        "description",
+        "readme",
+        "requires-python",
+        "license",
+        "authors",
+        "maintainers",
+        "keywords",
+        "classifiers",
+        "urls",
+        "scripts",
+        "gui-scripts",
+        "entry-points",
+        "dependencies",
+        "optional-dependencies",
+    }
+)
+
+
 class ProjectOverride(pydantic.BaseModel):
     """Override pyproject.toml settings
 
@@ -271,6 +292,9 @@ class ProjectOverride(pydantic.BaseModel):
         - ninja
       requires_external:
         - openssl-libs
+      add_dynamic_field:
+        - readme
+        - version
     """
 
     model_config = MODEL_CONFIG
@@ -296,13 +320,33 @@ class ProjectOverride(pydantic.BaseModel):
        ``tomlkit.loads(dist(pkgname).read_text("fromager-build-settings"))``.
     """
 
+    add_dynamic_field: list[str] = Field(default_factory=list)
+    """Add fields to ``[project] dynamic`` in pyproject.toml (PEP 621)
+
+    Each entry must be a valid PEP 621 dynamic field name.
+    See https://peps.python.org/pep-0621/#dynamic
+    """
+
     @pydantic.field_validator("update_build_requires")
     @classmethod
     def validate_update_build_requires(cls, v: list[str]) -> list[str]:
         for reqstr in v:
             Requirement(reqstr)
         return v
 
+    @pydantic.field_validator("add_dynamic_field")
+    @classmethod
+    def validate_add_dynamic_field(cls, v: list[str]) -> list[str]:
+        invalid = sorted(set(v) - PEP621_DYNAMIC_FIELDS)
+        if invalid:
+            allowed = sorted(PEP621_DYNAMIC_FIELDS)
+            raise ValueError(
+                f"invalid dynamic field(s): {invalid}. "
+                f"Allowed values per PEP 621: {allowed}. "
+                f"See https://peps.python.org/pep-0621/#dynamic"
+            )
+        return v
+
 
 class VariantInfo(pydantic.BaseModel):
     """Variant information for a package

src/fromager/pyproject.py

@@ -29,13 +29,16 @@ class PyprojectFix:
 
     - add missing pyproject.toml
     - add or update `[build-system] requires`
+    - add fields to `[project] dynamic` (PEP 621)
 
     Requirements in `update_build_requires` are added to
     `[build-system] requires`. If a requirement name matches an existing
     name, then the requirement is replaced.
 
     Requirements in `remove_build_requires` are removed from
     `[build-system] requires`.
+
+    Entries in `add_dynamic_field` are merged into `[project] dynamic`.
     """
 
     def __init__(
@@ -45,18 +48,21 @@ def __init__(
         build_dir: pathlib.Path,
         update_build_requires: list[str],
         remove_build_requires: list[NormalizedName],
+        add_dynamic_field: list[str] | None = None,
     ) -> None:
         self.req = req
         self.build_dir = build_dir
         self.update_requirements = update_build_requires
         self.remove_requirements = remove_build_requires
+        self.add_dynamic = add_dynamic_field or []
         self.pyproject_toml = self.build_dir / "pyproject.toml"
         self.setup_py = self.build_dir / "setup.py"
 
     def run(self) -> None:
         doc = self._load()
         build_system = self._default_build_system(doc)
         self._update_build_requires(build_system)
+        self._update_dynamic_fields(doc)
         logger.debug(
             "pyproject.toml %s: %s=%r, %s=%r",
             BUILD_SYSTEM,
@@ -132,6 +138,25 @@ def _update_build_requires(self, build_system: TomlDict) -> None:
                 new_requires,
             )
 
+    def _update_dynamic_fields(self, doc: tomlkit.TOMLDocument) -> None:
+        """Merge new entries into ``[project] dynamic``."""
+        if not self.add_dynamic:
+            return
+        project: TomlDict = doc.setdefault("project", {})
+        old_dynamic: list[str] = project.get("dynamic", [])
+        merged = list(old_dynamic)
+        for field in self.add_dynamic:
+            if field not in merged:
+                merged.append(field)
+        merged.sort()
+        if set(merged) != set(old_dynamic):
+            project["dynamic"] = merged
+            logger.info(
+                "changed project dynamic from %r to %r",
+                old_dynamic,
+                merged,
+            )
+
 
 def apply_project_override(
     ctx: context.WorkContext, req: Requirement, sdist_root_dir: pathlib.Path
@@ -140,17 +165,20 @@ def apply_project_override(
     pbi = ctx.package_build_info(req)
     update_build_requires = pbi.project_override.update_build_requires
     remove_build_requires = pbi.project_override.remove_build_requires
-    if update_build_requires or remove_build_requires:
+    add_dynamic_field = pbi.project_override.add_dynamic_field
+    if update_build_requires or remove_build_requires or add_dynamic_field:
         logger.debug(
             f"applying project_override: "
-            f"{update_build_requires=}, {remove_build_requires=}"
+            f"{update_build_requires=}, {remove_build_requires=}, "
+            f"{add_dynamic_field=}"
         )
         build_dir = pbi.build_dir(sdist_root_dir)
         PyprojectFix(
             req,
             build_dir=build_dir,
             update_build_requires=update_build_requires,
             remove_build_requires=remove_build_requires,
+            add_dynamic_field=add_dynamic_field,
         ).run()
     else:
         logger.debug("no project_override")

tests/test_packagesettings.py

@@ -10,6 +10,7 @@
 
 from fromager import build_environment, context
 from fromager.packagesettings import (
+    PEP621_DYNAMIC_FIELDS,
     Annotations,
     BuildDirectory,
     EnvVars,
@@ -77,6 +78,7 @@
         "remove_build_requires": ["cmake"],
         "update_build_requires": ["setuptools>=68.0.0", "torch"],
         "requires_external": ["openssl-libs"],
+        "add_dynamic_field": ["readme"],
     },
     "resolver_dist": {
         "include_sdists": True,
@@ -139,6 +141,7 @@
         "remove_build_requires": [],
         "update_build_requires": [],
         "requires_external": [],
+        "add_dynamic_field": [],
     },
     "resolver_dist": {
         "sdist_server_url": None,
@@ -180,6 +183,7 @@
         "remove_build_requires": [],
         "update_build_requires": [],
         "requires_external": [],
+        "add_dynamic_field": [],
     },
     "resolver_dist": {
         "sdist_server_url": None,
@@ -902,3 +906,44 @@ def test_version_none_no_reference(
     result = pbi.get_extra_environ(template_env={}, version=None)
     assert result["FOO"] == "bar"
     assert "__version__" not in result
+
+
+def test_add_dynamic_field_from_yaml() -> None:
+    ps = PackageSettings.from_string(
+        "test-pkg",
+        """
+project_override:
+    add_dynamic_field:
+        - readme
+        - version
+""",
+    )
+    assert ps.project_override.add_dynamic_field == ["readme", "version"]
+
+
+@pytest.mark.parametrize("invalid_field", ["name", "typo", "Name"])
+def test_add_dynamic_field_rejects_invalid(invalid_field: str) -> None:
+    with pytest.raises(RuntimeError, match="Allowed values per PEP 621"):
+        PackageSettings.from_string(
+            "test-pkg",
+            f"""
+project_override:
+    add_dynamic_field:
+        - {invalid_field}
+""",
+        )
+
+
+def test_add_dynamic_field_accepts_all_pep621_fields() -> None:
+    fields_yaml = "\n".join(f"        - {f}" for f in sorted(PEP621_DYNAMIC_FIELDS))
+    ps = PackageSettings.from_string(
+        "test-pkg",
+        f"""
+project_override:
+    add_dynamic_field:
+{fields_yaml}
+""",
+    )
+    assert sorted(ps.project_override.add_dynamic_field) == sorted(
+        PEP621_DYNAMIC_FIELDS
+    )

tests/test_pyproject.py

@@ -177,3 +177,66 @@ def test_pyproject_override_multiple_requires(tmp_path: pathlib.Path) -> None:
             "setuptools",
         ]
     ]
+
+
+def test_pyproject_add_dynamic_field_no_project_section(
+    tmp_path: pathlib.Path,
+) -> None:
+    tmp_path.joinpath("pyproject.toml").write_text(PYPROJECT_TOML)
+    req = Requirement("testproject==1.0.0")
+    fixer = pyproject.PyprojectFix(
+        req,
+        build_dir=tmp_path,
+        update_build_requires=[],
+        remove_build_requires=[],
+        add_dynamic_field=["readme", "version"],
+    )
+    fixer.run()
+    doc = tomlkit.loads(tmp_path.joinpath("pyproject.toml").read_text())
+    assert isinstance(doc["project"], typing.Container)
+    assert dict(doc["project"].items())["dynamic"] == ["readme", "version"]
+
+
+def test_pyproject_add_dynamic_field_merges_existing(
+    tmp_path: pathlib.Path,
+) -> None:
+    tmp_path.joinpath("pyproject.toml").write_text(
+        textwrap.dedent("""
+            [project]
+            name = "testproject"
+            dynamic = ["version", "description"]
+        """)
+    )
+    req = Requirement("testproject==1.0.0")
+    fixer = pyproject.PyprojectFix(
+        req,
+        build_dir=tmp_path,
+        update_build_requires=[],
+        remove_build_requires=[],
+        add_dynamic_field=["readme", "version"],
+    )
+    fixer.run()
+    doc = tomlkit.loads(tmp_path.joinpath("pyproject.toml").read_text())
+    assert isinstance(doc["project"], typing.Container)
+    assert dict(doc["project"].items())["dynamic"] == [
+        "description",
+        "readme",
+        "version",
+    ]
+
+
+def test_pyproject_add_dynamic_field_empty_list(
+    tmp_path: pathlib.Path,
+) -> None:
+    tmp_path.joinpath("pyproject.toml").write_text(PYPROJECT_TOML)
+    req = Requirement("testproject==1.0.0")
+    fixer = pyproject.PyprojectFix(
+        req,
+        build_dir=tmp_path,
+        update_build_requires=[],
+        remove_build_requires=[],
+        add_dynamic_field=[],
+    )
+    fixer.run()
+    doc = tomlkit.loads(tmp_path.joinpath("pyproject.toml").read_text())
+    assert "project" not in doc

tests/testdata/context/overrides/settings/test_pkg.yaml

@@ -36,6 +36,8 @@ project_override:
         - torch
     requires_external:
         - openssl-libs
+    add_dynamic_field:
+        - readme
 resolver_dist:
     sdist_server_url: https://sdist.test/egg
     include_sdists: true