Support TOML lists in cmake.define

Fixes #874

Author: alexreinking

src/scikit_build_core/builder/builder.py

@@ -245,12 +245,7 @@ def configure(
                 cmake_defines["CMAKE_OSX_ARCHITECTURES"] = ";".join(archs)
 
         # Add the pre-defined or passed CMake defines
-        cmake_defines.update(
-            {
-                k: ("TRUE" if v else "FALSE") if isinstance(v, bool) else v
-                for k, v in self.settings.cmake.define.items()
-            }
-        )
+        cmake_defines.update(self.settings.cmake.define)
 
         self.config.configure(
             defines=cmake_defines,

src/scikit_build_core/settings/skbuild_model.py

@@ -27,6 +27,21 @@ def __dir__() -> List[str]:
     return __all__
 
 
+class CMakeSettingsDefine(str):
+    def __new__(cls, raw: Union[str, bool, List[str]]) -> "CMakeSettingsDefine":
+        def escape_semicolons(item: str) -> str:
+            return item.replace(";", r"\;")
+
+        if isinstance(raw, bool):
+            value = "TRUE" if raw else "FALSE"
+        elif isinstance(raw, list):
+            value = ";".join(map(escape_semicolons, raw))
+        else:
+            value = raw
+
+        return super().__new__(cls, value)
+
+
 @dataclasses.dataclass
 class CMakeSettings:
     minimum_version: Optional[Version] = None
@@ -49,7 +64,7 @@ class CMakeSettings:
     in config or envvar will override toml. See also ``cmake.define``.
     """
 
-    define: Annotated[Dict[str, Union[str, bool]], "EnvVar"] = dataclasses.field(
+    define: Annotated[Dict[str, CMakeSettingsDefine], "EnvVar"] = dataclasses.field(
         default_factory=dict
     )
     """

tests/packages/cmake_defines/CMakeLists.txt

@@ -0,0 +1,20 @@
+cmake_minimum_required(VERSION 3.26)
+project(cmake_defines LANGUAGES NONE)
+
+set(ONE_LEVEL_LIST
+    ""
+    CACHE STRING "")
+set(NESTED_LIST
+    ""
+    CACHE STRING "")
+
+set(out_file "${CMAKE_CURRENT_BINARY_DIR}/log.txt")
+file(WRITE "${out_file}" "")
+
+foreach(list IN ITEMS ONE_LEVEL_LIST NESTED_LIST)
+  list(LENGTH ${list} length)
+  file(APPEND "${out_file}" "${list}.LENGTH = ${length}\n")
+  foreach(item IN LISTS ${list})
+    file(APPEND "${out_file}" "${item}\n")
+  endforeach()
+endforeach()

tests/packages/cmake_defines/pyproject.toml

@@ -0,0 +1,11 @@
+[tool.scikit-build]
+cmake.version = '>=3.26'
+
+[tool.scikit-build.cmake.define]
+ONE_LEVEL_LIST = [
+    "Foo",
+    "Bar",
+    "ExceptionallyLargeListEntryThatWouldOverflowTheLine",
+    "Baz",
+]
+NESTED_LIST = [ "Apple", "Lemon;Lime", "Banana" ]

tests/test_cmake_config.py

@@ -4,14 +4,17 @@
 import shutil
 import sysconfig
 from pathlib import Path
+from textwrap import dedent
 from typing import TYPE_CHECKING
 
 import pytest
 from packaging.specifiers import SpecifierSet
 from packaging.version import Version
 
+from scikit_build_core.builder.builder import Builder
 from scikit_build_core.cmake import CMake, CMaker
 from scikit_build_core.errors import CMakeNotFoundError
+from scikit_build_core.settings.skbuild_read_settings import SettingsReader
 
 if TYPE_CHECKING:
     from collections.abc import Generator
@@ -201,6 +204,41 @@ def test_cmake_paths(
     assert len(fp.calls) == 2
 
 
+@pytest.mark.configure
+def test_cmake_defines(
+    tmp_path: Path,
+):
+    source_dir = DIR / "packages" / "cmake_defines"
+    binary_dir = tmp_path / "build"
+
+    config = CMaker(
+        CMake.default_search(),
+        source_dir=source_dir,
+        build_dir=binary_dir,
+        build_type="Release",
+    )
+
+    reader = SettingsReader.from_file(source_dir / "pyproject.toml")
+
+    builder = Builder(reader.settings, config)
+    builder.configure(defines={})
+
+    configure_log = Path.read_text(binary_dir / "log.txt")
+    assert configure_log == dedent(
+        """\
+        ONE_LEVEL_LIST.LENGTH = 4
+        Foo
+        Bar
+        ExceptionallyLargeListEntryThatWouldOverflowTheLine
+        Baz
+        NESTED_LIST.LENGTH = 3
+        Apple
+        Lemon;Lime
+        Banana
+        """
+    )
+
+
 def test_get_cmake_via_envvar(monkeypatch: pytest.MonkeyPatch, fp):
     monkeypatch.setattr("shutil.which", lambda x: x)
     cmake_path = Path("some-prog")