fix: avoid PYTHON_VERSION breaking uv if set (#2795)

* fix: avoid PYTHON_VERSION breaking uv if set

* fix: also keep UV_PYTHON out

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* fix: specify the python version in the uv command more often

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* fix: revert env order change

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* Update windows.py

Co-authored-by: Joe Rickerby <joerick@mac.com>

---------

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>
Co-authored-by: Joe Rickerby <joerick@mac.com>

cibuildwheel/platforms/macos.py

@@ -253,6 +253,10 @@ def setup_python(
     # https://github.com/pypa/virtualenv/issues/620
     # Also see https://github.com/python/cpython/pull/9516
     env.pop("__PYVENV_LAUNCHER__", None)
+    # uv uses this over the current environment's python, so remove it to avoid confusion
+    env.pop("PYTHON_VERSION", None)
+    env.pop("PYTHON_ARCH", None)
+    env.pop("UV_PYTHON", None)
 
     # we version pip ourselves, so we don't care about pip version checking
     env["PIP_DISABLE_PIP_VERSION_CHECK"] = "1"
@@ -370,6 +374,8 @@ def setup_python(
                 uv_path,
                 "pip",
                 "install",
+                "--python",
+                which_python,
                 "--upgrade",
                 "delocate",
                 "build[virtualenv, uv]",
@@ -382,6 +388,8 @@ def setup_python(
                 uv_path,
                 "pip",
                 "install",
+                "--python",
+                which_python,
                 "--upgrade",
                 "delocate",
                 *constraint_flags(dependency_constraint),

cibuildwheel/platforms/windows.py

@@ -293,7 +293,9 @@ def setup_python(
     # set up environment variables for run_with_env
     env["PYTHON_VERSION"] = python_configuration.version
     env["PYTHON_ARCH"] = python_configuration.arch
-    env["PIP_DISABLE_PIP_VERSION_CHECK"] = "1"
+    env.pop("UV_PYTHON", None)
+    if not use_uv:
+        env["PIP_DISABLE_PIP_VERSION_CHECK"] = "1"
 
     # update env with results from CIBW_ENVIRONMENT
     env = environment.as_dictionary(prev_environment=env)
@@ -334,6 +336,8 @@ def setup_python(
                 uv_path,
                 "pip",
                 "install",
+                "--python",
+                where_python,
                 "--upgrade",
                 "build[virtualenv]",
                 *constraint_flags(dependency_constraint),