Remove redundant/legacy cargo_build_script.bzl (#2364)

COMPATIBILITY.md

@@ -72,7 +72,7 @@ that anything directly accessible from this file is considered stable.
 `//rust/private/…` is not subject to the backwards compatibility policy. Content
 of this package is an implementation detail.
 
-`//cargo:cargo_build_script.bzl` is subject to the backwards compatibility policy.
+`//cargo:defs.bzl` is subject to the backwards compatibility policy.
 
 `//cargo`, `//util`, `//tools`, `//test`, `//examples`, `//bindgen`, `//proto`,
 `//wasm_bindgen` and any packages not mentioned by this document are by default
@@ -88,7 +88,7 @@ They should be added to `//rust:incompatible.bzl`.
 Bug fixes are not a breaking change by default. We'll use Common Sense (and we
 will pull in more maintainers and the community to discuss) if we see a certain
 bug fix is controversial. Incompatible changes to
-`//cargo:cargo_build_script.bzl` that make `cargo_build_script` more accurately
+`//cargo:defs.bzl` that make `cargo_build_script` more accurately
 follow cargo's behaviour are considered bug fixes.
 
 ## How to make a backwards incompatible change?

cargo/cargo_build_script.bzl

@@ -1,16 +0,0 @@
-"""Legacy load locations for Cargo build script rules
-
-Instead, `defs.bzl` should be used.
-"""
-
-load(
-    "//cargo/private:cargo_build_script.bzl",
-    _cargo_dep_env = "cargo_dep_env",
-)
-load(
-    "//cargo/private:cargo_build_script_wrapper.bzl",
-    _cargo_build_script = "cargo_build_script",
-)
-
-cargo_build_script = _cargo_build_script
-cargo_dep_env = _cargo_dep_env

cargo/defs.bzl

@@ -1,5 +1,10 @@
 """Common definitions for the `@rules_rust//cargo` package"""
 
+load(
+    "//cargo/private:cargo_bootstrap.bzl",
+    _cargo_bootstrap_repository = "cargo_bootstrap_repository",
+    _cargo_env = "cargo_env",
+)
 load(
     "//cargo/private:cargo_build_script.bzl",
     _cargo_dep_env = "cargo_dep_env",
@@ -8,11 +13,6 @@ load(
     "//cargo/private:cargo_build_script_wrapper.bzl",
     _cargo_build_script = "cargo_build_script",
 )
-load(
-    ":cargo_bootstrap.bzl",
-    _cargo_bootstrap_repository = "cargo_bootstrap_repository",
-    _cargo_env = "cargo_env",
-)
 
 cargo_bootstrap_repository = _cargo_bootstrap_repository
 cargo_env = _cargo_env

cargo/features.bzl

@@ -1,6 +0,0 @@
-"""Public Cargo features for Bazel."""
-
-# `symlink-exec-root` feature will symlink the execroot to the build script execution directory.
-#
-# This is useful for building with hermetic C++ toolchains.
-SYMLINK_EXEC_ROOT_FEATURE = "symlink-exec-root"

cargo/private/cargo_build_script.bzl

@@ -4,16 +4,25 @@ load("@bazel_skylib//lib:paths.bzl", "paths")
 load("@bazel_skylib//rules:common_settings.bzl", "BuildSettingInfo")
 load("@bazel_tools//tools/build_defs/cc:action_names.bzl", "CPP_COMPILE_ACTION_NAME", "C_COMPILE_ACTION_NAME")
 load("@bazel_tools//tools/cpp:toolchain_utils.bzl", "find_cpp_toolchain")
-load("//cargo:features.bzl", "SYMLINK_EXEC_ROOT_FEATURE")
 load("//rust:defs.bzl", "rust_common")
 load("//rust:rust_common.bzl", "BuildInfo", "DepInfo")
 
 # buildifier: disable=bzl-visibility
-load("//rust/private:rustc.bzl", "get_compilation_mode_opts", "get_linker_and_args")
+load(
+    "//rust/private:rustc.bzl",
+    "get_compilation_mode_opts",
+    "get_linker_and_args",
+)
 
 # buildifier: disable=bzl-visibility
-load("//rust/private:utils.bzl", "dedent", "expand_dict_value_locations", "find_cc_toolchain", "find_toolchain", _name_to_crate_name = "name_to_crate_name")
-load(":features.bzl", "feature_enabled")
+load(
+    "//rust/private:utils.bzl",
+    "dedent",
+    "expand_dict_value_locations",
+    "find_cc_toolchain",
+    "find_toolchain",
+    _name_to_crate_name = "name_to_crate_name",
+)
 
 # Reexport for cargo_build_script_wrapper.bzl
 name_to_crate_name = _name_to_crate_name
@@ -70,6 +79,29 @@ def _pwd_flags(args):
             res.append(arg)
     return res
 
+def _feature_enabled(ctx, feature_name, default = False):
+    """Check if a feature is enabled.
+
+    If the feature is explicitly enabled or disabled, return accordingly.
+
+    In the case where the feature is not explicitly enabled or disabled, return the default value.
+
+    Args:
+        ctx: The context object.
+        feature_name: The name of the feature.
+        default: The default value to return if the feature is not explicitly enabled or disabled.
+
+    Returns:
+        Boolean defining whether the feature is enabled.
+    """
+    if feature_name in ctx.disabled_features:
+        return False
+
+    if feature_name in ctx.features:
+        return True
+
+    return default
+
 def _cargo_build_script_impl(ctx):
     """The implementation for the `cargo_build_script` rule.
 
@@ -244,7 +276,7 @@ def _cargo_build_script_impl(ctx):
             build_script_inputs.append(dep_build_info.out_dir)
 
     experimental_symlink_execroot = ctx.attr._experimental_symlink_execroot[BuildSettingInfo].value or \
-                                    feature_enabled(ctx, SYMLINK_EXEC_ROOT_FEATURE)
+                                    _feature_enabled(ctx, "symlink-exec-root")
 
     if experimental_symlink_execroot:
         env["RULES_RUST_SYMLINK_EXEC_ROOT"] = "1"

cargo/private/features.bzl

@@ -1,24 +0,0 @@
-"""Feature helpers."""
-
-def feature_enabled(ctx, feature_name, default = False):
-    """Check if a feature is enabled.
-
-    If the feature is explicitly enabled or disabled, return accordingly.
-
-    In the case where the feature is not explicitly enabled or disabled, return the default value.
-
-    Args:
-        ctx: The context object.
-        feature_name: The name of the feature.
-        default: The default value to return if the feature is not explicitly enabled or disabled.
-
-    Returns:
-        Boolean defining whether the feature is enabled.
-    """
-    if feature_name in ctx.disabled_features:
-        return False
-
-    if feature_name in ctx.features:
-        return True
-
-    return default

test/unit/build_script_deps/build_script_deps.bzl

@@ -1,7 +1,7 @@
 """Analysis tests for cargo_build_script."""
 
 load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")
-load("//cargo:cargo_build_script.bzl", "cargo_build_script")
+load("//cargo:defs.bzl", "cargo_build_script")
 load("//rust:defs.bzl", "rust_library")
 
 DepActionsInfo = provider(