Add extra_rustc_flag and extra_exec_rustc_flag

BUILD.bazel

@@ -1,5 +1,5 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
-load("//rust:defs.bzl", "capture_clippy_output", "clippy_flags", "error_format", "extra_exec_rustc_flags", "extra_rustc_flags")
+load("//rust:defs.bzl", "capture_clippy_output", "clippy_flags", "error_format", "extra_exec_rustc_flag", "extra_exec_rustc_flags", "extra_rustc_flag", "extra_rustc_flags")
 
 exports_files(["LICENSE"])
 
@@ -55,6 +55,12 @@ extra_rustc_flags(
     visibility = ["//visibility:public"],
 )
 
+extra_rustc_flag(
+    name = "extra_rustc_flag",
+    build_setting_default = "",
+    visibility = ["//visibility:public"],
+)
+
 # This setting may be used to pass extra options to rustc from the command line
 # in exec configuration.
 # It applies across all targets whereas the rustc_flags option on targets applies only
@@ -65,6 +71,12 @@ extra_exec_rustc_flags(
     visibility = ["//visibility:public"],
 )
 
+extra_exec_rustc_flag(
+    name = "extra_exec_rustc_flag",
+    build_setting_default = "",
+    visibility = ["//visibility:public"],
+)
+
 # This setting is used by the clippy rules. See https://bazelbuild.github.io/rules_rust/rust_clippy.html
 label_flag(
     name = "clippy.toml",

rust/defs.bzl

@@ -43,7 +43,9 @@ load(
 load(
     "//rust/private:rustc.bzl",
     _error_format = "error_format",
+    _extra_exec_rustc_flag = "extra_exec_rustc_flag",
     _extra_exec_rustc_flags = "extra_exec_rustc_flags",
+    _extra_rustc_flag = "extra_rustc_flag",
     _extra_rustc_flags = "extra_rustc_flags",
 )
 load(
@@ -102,9 +104,15 @@ capture_clippy_output = _capture_clippy_output
 error_format = _error_format
 # See @rules_rust//rust/private:rustc.bzl for a complete description.
 
+extra_rustc_flag = _extra_rustc_flag
+# See @rules_rust//rust/private:rustc.bzl for a complete description.
+
 extra_rustc_flags = _extra_rustc_flags
 # See @rules_rust//rust/private:rustc.bzl for a complete description.
 
+extra_exec_rustc_flag = _extra_exec_rustc_flag
+# See @rules_rust//rust/private:rustc.bzl for a complete description.
+
 extra_exec_rustc_flags = _extra_exec_rustc_flags
 # See @rules_rust//rust/private:rustc.bzl for a complete description.
 

rust/private/clippy.bzl

@@ -215,6 +215,7 @@ rust_clippy_aspect = aspect(
             doc = "The desired `--error-format` flags for clippy",
             default = "//:error_format",
         ),
+        "_extra_rustc_flag": attr.label(default = "//:extra_rustc_flag"),
         "_extra_rustc_flags": attr.label(default = "//:extra_rustc_flags"),
         "_process_wrapper": attr.label(
             doc = "A process wrapper for running clippy on all platforms",

rust/private/rust.bzl

@@ -666,13 +666,19 @@ _common_attrs = {
         cfg = "exec",
     ),
     "_error_format": attr.label(
-        default = Label("//:error_format"),
+        default = "//:error_format",
+    ),
+    "_extra_exec_rustc_flag": attr.label(
+        default = "//:extra_exec_rustc_flag",
     ),
     "_extra_exec_rustc_flags": attr.label(
-        default = Label("//:extra_exec_rustc_flags"),
+        default = "//:extra_exec_rustc_flags",
+    ),
+    "_extra_rustc_flag": attr.label(
+        default = "//:extra_rustc_flag",
     ),
     "_extra_rustc_flags": attr.label(
-        default = Label("//:extra_rustc_flags"),
+        default = "//:extra_rustc_flags",
     ),
     "_import_macro_dep": attr.label(
         default = Label("//util/import"),

rust/private/rustc.bzl

@@ -837,9 +837,15 @@ def construct_arguments(
     if hasattr(ctx.attr, "_extra_rustc_flags") and not is_exec_configuration(ctx):
         rustc_flags.add_all(ctx.attr._extra_rustc_flags[ExtraRustcFlagsInfo].extra_rustc_flags)
 
+    if hasattr(ctx.attr, "_extra_rustc_flag") and not is_exec_configuration(ctx):
+        rustc_flags.add_all(ctx.attr._extra_rustc_flag[ExtraRustcFlagsInfo].extra_rustc_flags)
+
     if hasattr(ctx.attr, "_extra_exec_rustc_flags") and is_exec_configuration(ctx):
         rustc_flags.add_all(ctx.attr._extra_exec_rustc_flags[ExtraExecRustcFlagsInfo].extra_exec_rustc_flags)
 
+    if hasattr(ctx.attr, "_extra_exec_rustc_flag") and is_exec_configuration(ctx):
+        rustc_flags.add_all(ctx.attr._extra_exec_rustc_flag[ExtraExecRustcFlagsInfo].extra_exec_rustc_flags)
+
     # Create a struct which keeps the arguments separate so each may be tuned or
     # replaced where necessary
     args = struct(
@@ -1520,6 +1526,18 @@ extra_rustc_flags = rule(
     build_setting = config.string_list(flag = True),
 )
 
+def _extra_rustc_flag_impl(ctx):
+    return ExtraRustcFlagsInfo(extra_rustc_flags = [f for f in ctx.build_setting_value if f != ""])
+
+extra_rustc_flag = rule(
+    doc = (
+        "Add additional rustc_flag from the command line with `--@rules_rust//:extra_rustc_flag`. " +
+        "Multiple uses are accumulated and appended after the extra_rustc_flags."
+    ),
+    implementation = _extra_rustc_flag_impl,
+    build_setting = config.string(flag = True, allow_multiple = True),
+)
+
 def _extra_exec_rustc_flags_impl(ctx):
     return ExtraExecRustcFlagsInfo(extra_exec_rustc_flags = ctx.build_setting_value)
 
@@ -1532,3 +1550,15 @@ extra_exec_rustc_flags = rule(
     implementation = _extra_exec_rustc_flags_impl,
     build_setting = config.string_list(flag = True),
 )
+
+def _extra_exec_rustc_flag_impl(ctx):
+    return ExtraExecRustcFlagsInfo(extra_exec_rustc_flags = [f for f in ctx.build_setting_value if f != ""])
+
+extra_exec_rustc_flag = rule(
+    doc = (
+        "Add additional rustc_flags in the exec configuration from the command line with `--@rules_rust//:extra_exec_rustc_flag`. " +
+        "Multiple uses are accumulated and appended after the extra_exec_rustc_flags."
+    ),
+    implementation = _extra_exec_rustc_flag_impl,
+    build_setting = config.string(flag = True, allow_multiple = True),
+)

test/extra_exec_rustc_flags/BUILD.bazel

@@ -21,15 +21,29 @@ rust_library(
 with_extra_exec_rustc_flags_cfg(
     name = "lib_with_exec_flags_do_not_build_directly",
     srcs = ["lib_do_not_build_directly"],
+    extra_exec_rustc_flag = [],
     extra_exec_rustc_flags = ["--cfg=bazel_exec"],
     tags = ["manual"],
 )
 
+with_extra_exec_rustc_flags_cfg(
+    name = "lib_with_singular_exec_flags_do_not_build_directly",
+    srcs = ["lib_do_not_build_directly"],
+    extra_exec_rustc_flag = ["--cfg=bazel_exec"],
+    extra_exec_rustc_flags = [],
+    tags = ["manual"],
+)
+
 with_exec_cfg(
     name = "lib",
     srcs = ["lib_with_exec_flags_do_not_build_directly"],
 )
 
+with_exec_cfg(
+    name = "lib_singular",
+    srcs = ["lib_with_singular_exec_flags_do_not_build_directly"],
+)
+
 # Checks that extra_exec_rustc_flags are not passed in non-exec configurations.
 # lib_no_exec.rs is a sample source file that fails to build if
 # `--cfg=bazel_exec` is present. The targets below are built in non-exec configurations,
@@ -43,14 +57,24 @@ rust_library(
 with_extra_exec_rustc_flags_cfg(
     name = "lib_no_exec_with_extra_build_flags",
     srcs = ["lib_no_exec"],
+    extra_exec_rustc_flag = [],
     extra_exec_rustc_flags = ["--cfg=bazel_exec"],
 )
 
+with_extra_exec_rustc_flags_cfg(
+    name = "lib_no_exec_with_singular_extra_build_flags",
+    srcs = ["lib_no_exec"],
+    extra_exec_rustc_flag = ["--cfg=bazel_exec"],
+    extra_exec_rustc_flags = [],
+)
+
 build_test(
     name = "lib_build",
     targets = [
         ":lib",
+        ":lib_singular",
         ":lib_no_exec",
         ":lib_no_exec_with_extra_build_flags",
+        ":lib_no_exec_with_singular_extra_build_flags",
     ],
 )

test/extra_exec_rustc_flags/defs.bzl

@@ -2,13 +2,14 @@
 
 def _extra_exec_rustc_flags_transition_impl(_settings, attr):
     return {
+        "//:extra_exec_rustc_flag": attr.extra_exec_rustc_flag,
         "//:extra_exec_rustc_flags": attr.extra_exec_rustc_flags,
     }
 
 _extra_exec_rustc_flags_transition = transition(
     implementation = _extra_exec_rustc_flags_transition_impl,
     inputs = [],
-    outputs = ["//:extra_exec_rustc_flags"],
+    outputs = ["//:extra_exec_rustc_flags", "//:extra_exec_rustc_flag"],
 )
 
 def _with_extra_exec_rustc_flags_cfg_impl(ctx):
@@ -17,6 +18,9 @@ def _with_extra_exec_rustc_flags_cfg_impl(ctx):
 with_extra_exec_rustc_flags_cfg = rule(
     implementation = _with_extra_exec_rustc_flags_cfg_impl,
     attrs = {
+        "extra_exec_rustc_flag": attr.string_list(
+            mandatory = True,
+        ),
         "extra_exec_rustc_flags": attr.string_list(
             mandatory = True,
         ),

test/unit/extra_rustc_flags/extra_rustc_flags_test.bzl

@@ -58,6 +58,20 @@ extra_rustc_flags_present_test = analysistest.make(
     },
 )
 
+extra_rustc_flag_present_test = analysistest.make(
+    _extra_rustc_flags_present_test,
+    attrs = {
+        "lib_exec": attr.label(
+            mandatory = True,
+            cfg = "exec",
+        ),
+    },
+    config_settings = {
+        "@//:extra_rustc_flag": [EXTRA_FLAG],
+        "@//:extra_rustc_flags": [],
+    },
+)
+
 def _define_test_targets():
     rust_library(
         name = "lib",
@@ -85,6 +99,12 @@ def extra_rustc_flags_test_suite(name):
         lib_exec = ":lib",
     )
 
+    extra_rustc_flag_present_test(
+        name = "extra_rustc_flag_present_test",
+        target_under_test = ":lib",
+        lib_exec = ":lib",
+    )
+
     native.test_suite(
         name = name,
         tests = [