Implement the build_dir format variables

Signed-off-by: Cristian Le <[email protected]>

Author: LecrisUT

src/scikit_build_core/build/_file_processor.py

@@ -7,6 +7,8 @@
 
 import pathspec
 
+from scikit_build_core.format import DummyFormatter
+
 if TYPE_CHECKING:
     from collections.abc import Generator, Sequence
 
@@ -51,12 +53,7 @@ def each_unignored_file(
         if p != Path(".gitignore")
     }
 
-    exclude_build_dir = build_dir.format(
-        cache_tag="*",
-        wheel_tag="*",
-        build_type="*",
-        state="*",
-    )
+    exclude_build_dir = build_dir.format(**DummyFormatter())
 
     exclude_lines = (
         [*EXCLUDE_LINES, exclude_build_dir] if exclude_build_dir else EXCLUDE_LINES

src/scikit_build_core/build/wheel.py

@@ -3,7 +3,6 @@
 import dataclasses
 import os
 import shutil
-import sys
 import sysconfig
 import tempfile
 from collections.abc import Mapping
@@ -20,6 +19,7 @@
 from ..builder.wheel_tag import WheelTag
 from ..cmake import CMake, CMaker
 from ..errors import FailedLiveProcessError
+from ..format import Formatter
 from ..settings.skbuild_read_settings import SettingsReader
 from ._editable import editable_redirect, libdir_to_installed, mapping_to_modules
 from ._init import setup_logging
@@ -279,10 +279,11 @@ def _build_wheel_impl_impl(
             build_dir = (
                 Path(
                     settings.build_dir.format(
-                        cache_tag=sys.implementation.cache_tag,
-                        wheel_tag=str(tags),
-                        build_type=settings.cmake.build_type,
-                        state=state,
+                        **Formatter(
+                            settings=settings,
+                            tags=tags,
+                            state=state,
+                        )
                     )
                 )
                 if settings.build_dir

src/scikit_build_core/format.py

@@ -3,15 +3,18 @@
 from __future__ import annotations
 
 import dataclasses
+import sys
 from collections.abc import Mapping
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, Literal
 
 if TYPE_CHECKING:
     from collections.abc import Iterator
 
+    from scikit_build_core.builder.wheel_tag import WheelTag
     from scikit_build_core.settings.skbuild_model import ScikitBuildSettings
 
 __all__ = [
+    "DummyFormatter",
     "Formatter",
 ]
 
@@ -22,18 +25,45 @@ class Formatter(Mapping[str, Any]):
 
     _dict: dict[str, Any] = dataclasses.field(init=False)
     """Dict storage of the acceptable variable keys and their expanded values."""
-    settings: ScikitBuildSettings
+    settings: ScikitBuildSettings | None = None
     """Parsed settings."""
+    state: (
+        Literal["sdist", "wheel", "editable", "metadata_wheel", "metadata_editable"]
+        | None
+    ) = None
+    tags: WheelTag | None = None
 
     def __getitem__(self, key: str) -> Any:
         return self._dict[key]
 
     def __len__(self) -> int:
-        return len(self._dict)
+        return len(list(iter(self)))
 
-    def __iter__(self) -> Iterator[Any]:
-        return iter(self._dict)
+    def __iter__(self) -> Iterator[str]:
+        # Filter out all the unknown/unset values so that when unpacking
+        # only the known/populated key-value pairs are expanded
+        for key in self._dict:
+            if self._dict[key] is not None:
+                yield key
 
     def __post_init__(self) -> None:
-        # TODO: Initialize the container with all known values
-        self._dict = {}
+        # For consistency and so that DummyFormatter can override all know keys,
+        # we define all the known keys or populate them with a `None`
+        self._dict = {
+            "cache_tag": sys.implementation.cache_tag,
+            "wheel_tag": str(self.tags) if self.tags else None,
+            "build_type": self.settings.cmake.build_type if self.settings else None,
+            "state": self.state if self.state else None,
+        }
+
+
+class DummyFormatter(Formatter):
+    """Dummy formatter that evaluates the formatting keys to dummy values."""
+
+    def __getitem__(self, key: str) -> str:
+        if key in self._dict:
+            return "*"
+        raise KeyError
+
+    def __iter__(self) -> Iterator[str]:
+        return iter(self._dict)

src/scikit_build_core/hatch/plugin.py

@@ -6,7 +6,6 @@
 import importlib.metadata
 import os
 import shutil
-import sys
 import sysconfig
 import tempfile
 import typing
@@ -24,6 +23,7 @@
 from ..builder.get_requires import GetRequires
 from ..builder.wheel_tag import WheelTag
 from ..cmake import CMake, CMaker
+from ..format import Formatter
 from ..settings.skbuild_read_settings import SettingsReader
 
 __all__ = ["ScikitBuildHook"]
@@ -162,10 +162,11 @@ def _initialize(self, *, build_data: dict[str, Any]) -> None:
         build_dir = (
             Path(
                 settings.build_dir.format(
-                    cache_tag=sys.implementation.cache_tag,
-                    wheel_tag=str(tags),
-                    build_type=settings.cmake.build_type,
-                    state=state,
+                    **Formatter(
+                        settings=settings,
+                        tags=tags,
+                        state=state,
+                    )
                 )
             )
             if settings.build_dir