WIP: [proposal] New patcher config

docs/conf.py

@@ -28,6 +28,7 @@
     "sphinxcontrib.autodoc_pydantic",
     "sphinx.ext.autodoc",
     "sphinx.ext.intersphinx",
+    "sphinxcontrib.spelling",
 ]
 
 # Enable MyST extensions to support reStructuredText directives in Markdown

docs/index.rst

@@ -39,6 +39,7 @@ those special cases directly into fromager.
    cli.rst
    glossary.rst
    develop.md
+   proposals/index.rst
 
 What's with the name?
 ---------------------

docs/proposals/index.rst

@@ -0,0 +1,7 @@
+Fromager Enhancement Proposals
+==============================
+
+.. toctree::
+   :maxdepth: 1
+
+   new-patcher-config

docs/proposals/new-patcher-config.md

@@ -0,0 +1,110 @@
+# New patcher configuration
+
+- Author: Christian Heimes
+- Created: 2026-02-26
+- Status: Open
+
+## What
+
+This enhancement document proposal a new approach to patch sources and wheel
+metadata through declarative configuration.
+
+## Why
+
+TODO
+
+## Goals
+
+- provide simple patching facilities with a declarative configuration approach
+- support version-specific patching (e.g. patch build system requirements for
+  `>=1.0,<1.0`).
+- make common tasks like fixing sdist metadata (`PKG-INFO`) easier
+- add patching of wheel and sdist package metadata to remove or modify
+  installation requirements (`requires-dist` field).
+
+## Non-goals
+
+- Patch files will not be deprecated and removed. Patches are still useful
+  and will be supported in the future.
+- CPU architecture-specific patches won't be supported, because they are a
+  misfeature. Patches will be
+
+## How
+
+The new system will use a new top-level configuration key `patch`, which is
+an array of patch operations. Each patch operation has a title, optional
+version specifier, and an action like `replace-line`, `fix-pkg-info`, or
+`pyproject-build-system`.
+
+- The action name acts as a tag ([discriminated union](https://docs.pydantic.dev/latest/concepts/unions/#discriminated-unions)).
+- The `title` is a human-readable description that explains the purpose of
+  the operation.
+- The optional field `when_version` can be used to limit the action,
+   e.g. `>=1.0,<1.0`.
+   > **NOTE**: `when_version` is not compatible with nightly builds.
+- Some actions have a `ignore_missing` boolean flag. If an action has no
+  effect, then it fails and stops the build unless `ignore_missing` is set.
+
+Example:
+
+```yaml
+patch:
+  - title: Comment out 'foo' requirement for version >= 1.2
+    action: replace-line
+    files:
+      - 'requirements.txt'
+    search: '^(foo.*)$'
+    replace: '# \\1'
+    when_version: '>=1.2'
+    ignore_missing: true
+
+  - title: Remove 'bar' from constraints.txt
+    action: delete-line
+    files:
+      - 'constraints.txt'
+    search: 'bar.*'
+
+  - title: Remove 'somepackage' installation requirement
+    action: remove-install-requires
+    requirement: somepackage
+
+  - title: Fix PKG-INFO metadata version
+    action: fix-pkg-info
+    metadata_version: '2.4'
+    when_version: '<1.0'
+
+  - title: Add missing setuptools to pyproject.toml
+    action: pyproject-build-system
+    update_build_requires:
+      - setuptools
+
+   - title: Update Torch install requirement to version in build env
+    action: pin-install-requires-to-build
+    requirement: torch
+```
+
+### Actions
+
+All file names are relative to `sdist_root_dir`.
+
+- The `replace-line` action replaces lines in one or more files.
+
+- The `delete-line` action removes a line from one or more files.
+
+- The `pyproject-build-system` action replaces the old `project_override`
+  settings `update_build_requires` and `remove_build_requires`.
+
+- The `remove-install-requires` action removes a `requires-dist` entry from
+  sdist and wheel installation requirements. The requirement is matched by
+  name-only or by full requirement (including specifier set and markers).
+
+- The `pin-install-requires-to-build` pins `requires-dist` in sdist
+  and wheel metadata to the exact version in the build environment. The
+  primary use case is Torch. If a package is build with Torch 2.9.1, then
+  we want the wheel to depend on exactly `torch==2.9.1`.
+
+### Deprecations
+
+The old settings `project_override.update_build_requires` and
+`project_override.remove_build_requires` will be deprecated and eventually
+removed.

docs/spelling_wordlist.txt

@@ -0,0 +1,66 @@
+args
+backend
+backend
+backends
+canonicalize
+changelog
+changelogs
+cheeseshop
+codebase
+config
+containerfile
+cpu
+customizations
+cython
+deprecations
+downloader
+env
+filesystem
+fromager
+frontend
+frontends
+graphviz
+iterable
+json
+linter
+localhost
+matcher
+mypy
+namespace
+numpy
+openssl
+platlib
+podman
+pre
+prebuilt
+purelib
+py
+pydantic
+pypi
+pyproject
+repo
+sdist
+sdists
+setuptools
+stderr
+stdin
+stdout
+subcommands
+subdirectory
+submodule
+submodules
+subprocesses
+toml
+toplevel
+traceback
+tracebacks
+txt
+unshare
+url
+urls
+vendored
+vendoring
+versionless
+virtualenv
+whitespace
+yaml

pyproject.toml

@@ -85,6 +85,7 @@ docs = [
     "myst-parser",
     "sphinx-rtd-theme",
     "autodoc-pydantic",
+    "sphinxcontrib.spelling",
 ]
 
 [project.urls]