Unpin numpy 2 for install, build against numpy rc for isolated builds

.github/workflows/cibuildwheel.yml

@@ -94,10 +94,10 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       CIBW_BEFORE_BUILD: >-
-        pip install certifi numpy>=1.25 &&
+        pip install certifi &&
         rm -rf {package}/build
       CIBW_BEFORE_BUILD_WINDOWS: >-
-        pip install certifi delvewheel numpy>=1.25 &&
+        pip install certifi delvewheel &&
         rm -rf {package}/build
       CIBW_REPAIR_WHEEL_COMMAND_WINDOWS: >-
         delvewheel repair -w {dest_dir} {wheel}

pyproject.toml

@@ -2,10 +2,21 @@
 build-backend = "setuptools.build_meta"
 requires = [
     "certifi>=2020.06.20",
-    "numpy>=1.25",
     "pybind11>=2.6",
     "setuptools>=64",
     "setuptools_scm>=7",
+
+    # Comments on numpy build requirement range:
+    #
+    #   1. >=2.0.x is the numpy requirement for wheel builds for distribution
+    #      on PyPI - building against 2.x yields wheels that are also
+    #      ABI-compatible with numpy 1.x at runtime.
+    #   2. Note that building against numpy 1.x works fine too - users and
+    #      redistributors can do this by installing the numpy version they like
+    #      and disabling build isolation.
+    #   3. The <2.3 upper bound is for matching the numpy deprecation policy,
+    #      it should not be loosened.
+    "numpy>=2.0.0rc1,<2.3",
 ]
 
 [tool.setuptools_scm]

setup.py

@@ -333,7 +333,7 @@ def make_release_tree(self, base_dir, files):
         "cycler>=0.10",
         "fonttools>=4.22.0",
         "kiwisolver>=1.3.1",
-        "numpy>=1.21,<2",
+        "numpy>=1.21",
         "packaging>=20.0",
         "pillow>=8",
         "pyparsing>=2.3.1",