refactor: API for deriving customized versions of the base rules

docs/BUILD.bazel

@@ -103,11 +103,14 @@ sphinx_stardocs(
         "//python/cc:py_cc_toolchain_bzl",
         "//python/cc:py_cc_toolchain_info_bzl",
         "//python/entry_points:py_console_script_binary_bzl",
+        "//python/private:attr_builders_bzl",
+        "//python/private:builders_util_bzl",
         "//python/private:py_binary_rule_bzl",
         "//python/private:py_cc_toolchain_rule_bzl",
         "//python/private:py_library_rule_bzl",
         "//python/private:py_runtime_rule_bzl",
         "//python/private:py_test_rule_bzl",
+        "//python/private:rule_builders_bzl",
         "//python/private/api:py_common_api_bzl",
         "//python/private/pypi:config_settings_bzl",
         "//python/private/pypi:pkg_aliases_bzl",

docs/_includes/field_kwargs_doc.md

@@ -0,0 +1,11 @@
+:::{field} kwargs
+:type: dict[str, Any]
+
+Additional kwargs to use when building. This is to allow manipulations that
+aren't directly supported by the builder's API. The state of this dict
+may or may not reflect prior API calls, and subsequent API calls may
+modify this dict. The general contract is that modifications to this will
+be respected when `build()` is called, assuming there were no API calls
+in between.
+:::
+

python/private/BUILD.bazel

@@ -51,10 +51,20 @@ filegroup(
     visibility = ["//python:__pkg__"],
 )
 
+bzl_library(
+    name = "attr_builders_bzl",
+    srcs = ["attr_builders.bzl"],
+    deps = [
+        ":builders_util_bzl",
+        "@bazel_skylib//lib:types",
+    ],
+)
+
 bzl_library(
     name = "attributes_bzl",
     srcs = ["attributes.bzl"],
     deps = [
+        ":attr_builders_bzl",
         ":common_bzl",
         ":enum_bzl",
         ":flags_bzl",
@@ -92,6 +102,14 @@ bzl_library(
     ],
 )
 
+bzl_library(
+    name = "builders_util_bzl",
+    srcs = ["builders_util.bzl"],
+    deps = [
+        "@bazel_skylib//lib:types",
+    ],
+)
+
 bzl_library(
     name = "bzlmod_enabled_bzl",
     srcs = ["bzlmod_enabled.bzl"],
@@ -283,6 +301,7 @@ bzl_library(
     deps = [
         ":attributes_bzl",
         ":py_executable_bzl",
+        ":rule_builders_bzl",
         ":semantics_bzl",
         "@bazel_skylib//lib:dicts",
     ],
@@ -410,6 +429,7 @@ bzl_library(
         ":flags_bzl",
         ":py_cc_link_params_info_bzl",
         ":py_internal_bzl",
+        ":rule_builders_bzl",
         ":toolchain_types_bzl",
         "@bazel_skylib//lib:dicts",
         "@bazel_skylib//rules:common_settings",
@@ -475,6 +495,7 @@ bzl_library(
         ":py_internal_bzl",
         ":py_runtime_info_bzl",
         ":reexports_bzl",
+        ":rule_builders_bzl",
         ":util_bzl",
         "@bazel_skylib//lib:dicts",
         "@bazel_skylib//lib:paths",
@@ -515,6 +536,7 @@ bzl_library(
         ":attributes_bzl",
         ":common_bzl",
         ":py_executable_bzl",
+        ":rule_builders_bzl",
         ":semantics_bzl",
         "@bazel_skylib//lib:dicts",
     ],
@@ -563,6 +585,16 @@ bzl_library(
     srcs = ["repo_utils.bzl"],
 )
 
+bzl_library(
+    name = "rule_builders_bzl",
+    srcs = ["rule_builders.bzl"],
+    deps = [
+        ":builders_bzl",
+        ":builders_util_bzl",
+        "@bazel_skylib//lib:types",
+    ],
+)
+
 bzl_library(
     name = "semver_bzl",
     srcs = ["semver.bzl"],