[WIP] Introduce a new editable mode build-dir

docs/reference/configs.md

@@ -249,7 +249,7 @@ print(mk_skbuild_docs())
 
 ```{eval-rst}
 .. confval:: editable.mode
-  :type: ``"redirect" | "inplace"``
+  :type: ``"redirect" | "inplace" | "build-dir"``
   :default: "redirect"
 
   Select the editable mode to use. Can be "redirect" (default) or "inplace".

src/scikit_build_core/build/_editable.py

@@ -14,13 +14,44 @@
 if typing.TYPE_CHECKING:
     from collections.abc import Sequence
 
-__all__ = ["editable_redirect", "libdir_to_installed", "mapping_to_modules"]
+__all__ = [
+    "editable_build_dir",
+    "editable_redirect",
+    "libdir_to_installed",
+    "mapping_to_modules",
+]
 
 
 def __dir__() -> list[str]:
     return __all__
 
 
+def editable_build_dir(
+    *,
+    source_files: dict[str, str],
+) -> str:
+    """
+    Prepare the contents of the _editable_redirect.py file as build-dir mode.
+    """
+
+    # We can reuse the `_editable_redirect.py` file without the rebuild/install
+    # feature and providing only source files to map.
+    editable_py = resources / "_editable_redirect.py"
+    editable_txt: str = editable_py.read_text(encoding="utf-8")
+
+    # Wheel_files are always empty here.
+    wheel_files: dict[str, str] = {}
+
+    arguments = (
+        source_files,  # known_source_files
+        wheel_files,  # known_wheel_files
+        None,  # path
+    )
+    arguments_str = ", ".join(repr(x) for x in arguments)
+    editable_txt += f"\n\ninstall({arguments_str})\n"
+    return editable_txt
+
+
 def editable_redirect(
     *,
     modules: dict[str, str],

src/scikit_build_core/build/wheel.py

@@ -23,7 +23,12 @@
 from ..errors import FailedLiveProcessError
 from ..format import pyproject_format
 from ..settings.skbuild_read_settings import SettingsReader
-from ._editable import editable_redirect, libdir_to_installed, mapping_to_modules
+from ._editable import (
+    editable_build_dir,
+    editable_redirect,
+    libdir_to_installed,
+    mapping_to_modules,
+)
 from ._init import setup_logging
 from ._pathutil import (
     packages_to_file_mapping,
@@ -56,22 +61,36 @@ def _make_editable(
     settings: ScikitBuildSettings,
     wheel: WheelWriter,
     packages: Iterable[str],
+    mode: Literal["redirect", "inplace", "build-dir"],
 ) -> None:
     modules = mapping_to_modules(mapping, libdir)
     installed = libdir_to_installed(libdir)
     if settings.wheel.install_dir.startswith("/"):
         msg = "Editable installs cannot rebuild an absolute wheel.install-dir. Use an override to change if needed."
         raise AssertionError(msg)
-    editable_txt = editable_redirect(
-        modules=modules,
-        installed=installed,
-        reload_dir=reload_dir,
-        rebuild=settings.editable.rebuild,
-        verbose=settings.editable.verbose,
-        build_options=build_options,
-        install_options=install_options,
-        install_dir=settings.wheel.install_dir,
-    )
+    if mode == "redirect":
+        editable_txt = editable_redirect(
+            modules=modules,
+            installed=installed,
+            reload_dir=reload_dir,
+            rebuild=settings.editable.rebuild,
+            verbose=settings.editable.verbose,
+            build_options=build_options,
+            install_options=install_options,
+            install_dir=settings.wheel.install_dir,
+        )
+    elif mode == "build-dir":
+        if not settings.build_dir:
+            msg = "Editable mode build-dir must have the build-dir option set."
+            raise ValueError(msg)
+        source_files = modules
+        # TODO: get the source files from the build-dir
+        editable_txt = editable_build_dir(
+            source_files=source_files,
+        )
+    else:
+        msg = f"Unexpected editable mode used: {mode}"
+        raise NotImplementedError(msg)
 
     wheel.writestr(
         f"_{name}_editable.py",
@@ -500,7 +519,7 @@ def _build_wheel_impl_impl(
             str_pkgs = (
                 str(Path.cwd().joinpath(p).parent.resolve()) for p in packages.values()
             )
-            if editable and settings.editable.mode == "redirect":
+            if editable and settings.editable.mode in ("redirect", "build-dir"):
                 reload_dir = build_dir.resolve() if settings.build_dir else None
 
                 _make_editable(
@@ -513,6 +532,7 @@ def _build_wheel_impl_impl(
                     wheel=wheel,
                     name=normalized_name,
                     packages=str_pkgs,
+                    mode=settings.editable.mode,
                 )
             elif editable and settings.editable.mode == "inplace":
                 if not packages:

src/scikit_build_core/resources/scikit-build.schema.json

@@ -260,7 +260,8 @@
         "mode": {
           "enum": [
             "redirect",
-            "inplace"
+            "inplace",
+            "build-dir"
           ],
           "default": "redirect",
           "description": "Select the editable mode to use. Can be \"redirect\" (default) or \"inplace\"."

src/scikit_build_core/settings/skbuild_model.py

@@ -327,7 +327,7 @@ class BackportSettings:
 
 @dataclasses.dataclass
 class EditableSettings:
-    mode: Literal["redirect", "inplace"] = "redirect"
+    mode: Literal["redirect", "inplace", "build-dir"] = "redirect"
     """
     Select the editable mode to use. Can be "redirect" (default) or "inplace".
     """