feat: Introduce an experimental uv toolchain

examples/bzlmod/MODULE.bazel

@@ -43,6 +43,13 @@ python.toolchain(
 # rules based on the `python_version` arg values.
 use_repo(python, "python_3_10", "python_3_9", "python_versions")
 
+# EXPERIMENTAL: This is experimental and may be removed without notice
+uv = use_extension("@rules_python//python/uv:extensions.bzl", "uv")
+uv.toolchain(uv_version = "0.2.23")
+use_repo(uv, "uv_toolchains")
+
+register_toolchains("@uv_toolchains//:all")
+
 # This extension allows a user to create modifications to how rules_python
 # creates different wheel repositories.  Different attributes allow the user
 # to modify the BUILD file, and copy files.

python/BUILD.bazel

@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 """This package contains two sets of rules:
 
     1) the "core" Python rules, which were historically bundled with Bazel and
@@ -41,6 +42,7 @@ filegroup(
         "//python/pip_install:distribution",
         "//python/private:distribution",
         "//python/runfiles:distribution",
+        "//python/uv:distribution",
     ],
     visibility = ["//:__pkg__"],
 )

python/private/python.bzl

@@ -17,6 +17,7 @@
 load("@bazel_features//:features.bzl", "bazel_features")
 load("//python:repositories.bzl", "python_register_toolchains")
 load(":pythons_hub.bzl", "hub_repo")
+load(":text_util.bzl", "render")
 load(":toolchains_repo.bzl", "multi_toolchain_aliases")
 load(":util.bzl", "IS_BAZEL_6_4_OR_HIGHER")
 
@@ -25,20 +26,6 @@ load(":util.bzl", "IS_BAZEL_6_4_OR_HIGHER")
 _MAX_NUM_TOOLCHAINS = 9999
 _TOOLCHAIN_INDEX_PAD_LENGTH = len(str(_MAX_NUM_TOOLCHAINS))
 
-def _toolchain_prefix(index, name):
-    """Prefixes the given name with the index, padded with zeros to ensure lexicographic sorting.
-
-    Examples:
-      _toolchain_prefix(   2, "foo") == "_0002_foo_"
-      _toolchain_prefix(2000, "foo") == "_2000_foo_"
-    """
-    return "_{}_{}_".format(_left_pad_zero(index, _TOOLCHAIN_INDEX_PAD_LENGTH), name)
-
-def _left_pad_zero(index, length):
-    if index < 0:
-        fail("index must be non-negative")
-    return ("0" * length + str(index))[-length:]
-
 # Printing a warning msg not debugging, so we have to disable
 # the buildifier check.
 # buildifier: disable=print
@@ -202,7 +189,7 @@ def _python_impl(module_ctx):
         name = "pythons_hub",
         default_python_version = default_toolchain.python_version,
         toolchain_prefixes = [
-            _toolchain_prefix(index, toolchain.name)
+            render.toolchain_prefix(index, toolchain.name, _TOOLCHAIN_INDEX_PAD_LENGTH)
             for index, toolchain in enumerate(toolchains)
         ],
         toolchain_python_versions = [t.python_version for t in toolchains],

python/private/text_util.bzl

@@ -99,11 +99,27 @@ def _render_tuple(items, *, value_repr = repr):
         ")",
     ])
 
+def _toolchain_prefix(index, name, pad_length):
+    """Prefixes the given name with the index, padded with zeros to ensure lexicographic sorting.
+
+    Examples:
+      toolchain_prefix(   2, "foo", 4) == "_0002_foo_"
+      toolchain_prefix(2000, "foo", 4) == "_2000_foo_"
+    """
+    return "_{}_{}_".format(_left_pad_zero(index, pad_length), name)
+
+def _left_pad_zero(index, length):
+    if index < 0:
+        fail("index must be non-negative")
+    return ("0" * length + str(index))[-length:]
+
 render = struct(
     alias = _render_alias,
     dict = _render_dict,
     indent = _indent,
+    left_pad_zero = _left_pad_zero,
     list = _render_list,
     select = _render_select,
     tuple = _render_tuple,
+    toolchain_prefix = _toolchain_prefix,
 )

python/uv/BUILD.bazel

@@ -0,0 +1,78 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# EXPERIMENTAL: This is experimental and may be removed without notice
+
+load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("//python/uv/private:current_toolchain.bzl", "current_toolchain")
+
+package(default_visibility = ["//:__subpackages__"])
+
+filegroup(
+    name = "distribution",
+    srcs = glob(["**"]) + [
+        "//python/uv/private:distribution",
+    ],
+    visibility = ["//:__subpackages__"],
+)
+
+# For stardoc to reference the files
+exports_files(["defs.bzl"])
+
+toolchain_type(
+    name = "uv_toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+current_toolchain(
+    name = "current_toolchain",
+    # Marked manual so that `bazel test //...` passes
+    # even if no toolchain is registered.
+    tags = ["manual"],
+    # EXPERIMENTAL: Visibility is restricted to allow for changes.
+    visibility = ["@rules_python//examples:__subpackages__"],
+)
+
+bzl_library(
+    name = "defs",
+    srcs = ["defs.bzl"],
+    # EXPERIMENTAL: Visibility is restricted to allow for changes.
+    visibility = ["//:__subpackages__"],
+)
+
+bzl_library(
+    name = "extensions",
+    srcs = ["extensions.bzl"],
+    # EXPERIMENTAL: Visibility is restricted to allow for changes.
+    visibility = ["//:__subpackages__"],
+    deps = [":repositories"],
+)
+
+bzl_library(
+    name = "repositories",
+    srcs = ["repositories.bzl"],
+    # EXPERIMENTAL: Visibility is restricted to allow for changes.
+    visibility = ["//:__subpackages__"],
+    deps = [
+        "//python/uv/private:toolchains_repo",
+        "//python/uv/private:versions",
+    ],
+)
+
+bzl_library(
+    name = "toolchain",
+    srcs = ["toolchain.bzl"],
+    # EXPERIMENTAL: Visibility is restricted to allow for changes.
+    visibility = ["//:__subpackages__"],
+)

python/uv/defs.bzl

@@ -0,0 +1,23 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+EXPERIMENTAL: This is experimental and may be removed without notice
+
+A toolchain for uv
+"""
+
+load("//python/uv/private:providers.bzl", _UvToolchainInfo = "UvToolchainInfo")
+
+UvToolchainInfo = _UvToolchainInfo

python/uv/extensions.bzl

@@ -0,0 +1,50 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+EXPERIMENTAL: This is experimental and may be removed without notice
+
+A module extension for working with uv.
+"""
+
+load("//python/uv:repositories.bzl", "uv_register_toolchains")
+
+_DOC = """\
+A module extension for working with uv.
+"""
+
+uv_toolchain = tag_class(attrs = {
+    "uv_version": attr.string(doc = "Explicit version of uv.", mandatory = True),
+})
+
+def _uv_toolchain_extension(module_ctx):
+    for mod in module_ctx.modules:
+        for toolchain in mod.tags.toolchain:
+            if not mod.is_root:
+                fail(
+                    "Only the root module may configure the uv toolchain.",
+                    "This prevents conflicting registrations with any other modules.",
+                    "NOTE: We may wish to enforce a policy where toolchain configuration is only allowed in the root module, or in rules_python. See https://github.com/bazelbuild/bazel/discussions/22024",
+                )
+
+            uv_register_toolchains(
+                uv_version = toolchain.uv_version,
+                register_toolchains = False,
+            )
+
+uv = module_extension(
+    doc = _DOC,
+    implementation = _uv_toolchain_extension,
+    tag_classes = {"toolchain": uv_toolchain},
+)

python/uv/private/BUILD.bazel

@@ -0,0 +1,45 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+
+filegroup(
+    name = "distribution",
+    srcs = glob(["**"]),
+    visibility = ["//python/uv:__pkg__"],
+)
+
+bzl_library(
+    name = "current_toolchain",
+    srcs = ["current_toolchain.bzl"],
+    visibility = ["//python/uv:__subpackages__"],
+)
+
+bzl_library(
+    name = "toolchain_types",
+    srcs = ["toolchain_types.bzl"],
+    visibility = ["//python/uv:__subpackages__"],
+)
+
+bzl_library(
+    name = "toolchains_repo",
+    srcs = ["toolchains_repo.bzl"],
+    visibility = ["//python/uv:__subpackages__"],
+)
+
+bzl_library(
+    name = "versions",
+    srcs = ["versions.bzl"],
+    visibility = ["//python/uv:__subpackages__"],
+)

python/uv/private/current_toolchain.bzl

@@ -0,0 +1,56 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""This module implements an alias rule to the resolved toolchain.
+"""
+
+load("//python/uv/private:toolchain_types.bzl", "UV_TOOLCHAIN_TYPE")
+
+_DOC = """\
+Exposes a concrete toolchain which is the result of Bazel resolving the
+toolchain for the execution or target platform.
+Workaround for https://github.com/bazelbuild/bazel/issues/14009
+"""
+
+# Forward all the providers
+def _current_toolchain_impl(ctx):
+    toolchain_info = ctx.toolchains[UV_TOOLCHAIN_TYPE]
+
+    # Bazel requires executable rules to create the executable themselves,
+    # so we create a symlink in this rule so that it appears this rule created its executable.
+    original_uv_executable = toolchain_info.uv_toolchain_info.uv[DefaultInfo].files_to_run.executable
+    symlink_uv_executable = ctx.actions.declare_file("uv_symlink_{}".format(original_uv_executable.basename))
+    ctx.actions.symlink(output = symlink_uv_executable, target_file = original_uv_executable)
+
+    new_default_info = DefaultInfo(
+        files = depset([symlink_uv_executable]),
+        runfiles = toolchain_info.default_info.default_runfiles,
+        executable = symlink_uv_executable,
+    )
+
+    return [
+        toolchain_info,
+        new_default_info,
+        toolchain_info.template_variable_info,
+        toolchain_info.uv_toolchain_info,
+    ]
+
+# Copied from java_toolchain_alias
+# https://cs.opensource.google/bazel/bazel/+/master:tools/jdk/java_toolchain_alias.bzl
+current_toolchain = rule(
+    implementation = _current_toolchain_impl,
+    toolchains = [UV_TOOLCHAIN_TYPE],
+    doc = _DOC,
+    executable = True,
+)

python/uv/private/providers.bzl

@@ -0,0 +1,31 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""This module contains the definitions of all providers."""
+
+UvToolchainInfo = provider(
+    doc = "Information about how to invoke the uv executable.",
+    fields = {
+        "uv": """
+:type: Target
+
+The uv binary `Target`
+""",
+        "version": """
+:type: str
+
+The uv version
+""",
+    },
+)