fix(uv): Transition build deps of whls back to libs

uv/private/BUILD.bazel

@@ -1,10 +1,15 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("@with_cfg.bzl", "original_settings")
 
 package(default_visibility = [
     "//docs:__pkg__",
     "//uv/private:__subpackages__",
 ])
 
+original_settings(
+    name = "py_library_original_settings",
+)
+
 bzl_library(
     name = "extension",
     srcs = ["extension.bzl"],

uv/private/defs.bzl

@@ -3,4 +3,24 @@
 load("@with_cfg.bzl", "with_cfg")
 load("//py:defs.bzl", "py_library")
 
-py_whl_library, _ = with_cfg(py_library).set(Label("//uv/private/constraints:lib_mode"), "whl").build()
+LIB_MODE = "//uv/private/constraints:lib_mode"
+
+py_whl_library, _ = with_cfg(py_library).set(Label(LIB_MODE), "whl").build()
+
+def _lib_mode_transition_impl(settings, attr):
+    return {LIB_MODE: "lib"}
+
+lib_mode_transition = transition(
+    implementation = _lib_mode_transition_impl,
+    inputs = [],
+    outputs = [LIB_MODE],
+)
+
+def _whl_mode_transition_impl(settings, attr):
+    return {LIB_MODE: "whl"}
+
+whl_mode_transition = transition(
+    implementation = _whl_mode_transition_impl,
+    inputs = [],
+    outputs = [LIB_MODE],
+)

uv/private/sdist_build/rule.bzl

@@ -6,6 +6,7 @@ load("//py/private/py_venv:types.bzl", "VirtualenvInfo")
 
 # buildifier: disable=bzl-visibility
 load("//py/private/toolchain:types.bzl", "PY_TOOLCHAIN")
+load("//uv/private:defs.bzl", "lib_mode_transition")
 
 TAR_TOOLCHAIN = "@tar.bzl//tar/toolchain:type"
 # UV_TOOLCHAIN = "@multitool//tools/uv:toolchain_type"
@@ -102,4 +103,13 @@ specified Python dependencies under the configured Python toochain.
         # UV_TOOLCHAIN,
         # FIXME: Add in a cc toolchain here
     ],
+    # KLUDGE: Reset the uv lib mode and force it to lib. This ensures that if
+    # the user requests a library graph as whl files instead of libraries AND we
+    # have to do an sdist build to create one of those whls, the sdist builds
+    # required to produce those whls will occur with their dependencies
+    # _installed as libraries_ rather than _present as whl files_.
+    #
+    # Otherwise the transitive deps of the venv will still be in whl mode and we
+    # get cool errors that `build` and other tools aren't installed.
+    cfg = lib_mode_transition,
 )