provide flag to exclude data at compile time

Fixes #2977

Author: ajwerner

crate_universe/BUILD.bazel

@@ -93,6 +93,7 @@ alias(
 rust_test(
     name = "unit_test",
     aliases = aliases(),
+    compile_data = glob(["test_data/**"]),
     crate = ":cargo_bazel",
     data = glob(["test_data/**"]) + [
         "//crate_universe/test_data/serialized_configs",

rust/private/rustc.bzl

@@ -715,8 +715,14 @@ def collect_inputs(
         if build_info.flags:
             build_info_inputs.append(build_info.flags)
 
+    # The old default behavior was to include data files at compile time.
+    # This flag controls whether to include data files in compile_data.
+    data_included_in_inputs = []
+    if not toolchain._incompatible_do_not_include_data_in_compile_data:
+        data_included_in_inputs = getattr(files, "data", [])
+
     nolinkstamp_compile_inputs = depset(
-        getattr(files, "data", []) +
+        data_included_in_inputs +
         build_info_inputs +
         ([toolchain.target_json] if toolchain.target_json else []) +
         ([] if linker_script == None else [linker_script]),

rust/settings/BUILD.bazel

@@ -253,3 +253,11 @@ per_crate_rustc_flag(
     build_setting_default = [],
     visibility = ["//visibility:public"],
 )
+
+# A flag to control whether to include data files in compile_data.
+incompatible_flag(
+    name = "incompatible_do_not_include_data_in_compile_data",
+    build_setting_default = False,
+    issue = "https://github.com/bazelbuild/rules_rust/issues/2977",
+    visibility = ["//visibility:public"],
+)

rust/toolchain.bzl

@@ -699,6 +699,7 @@ def _rust_toolchain_impl(ctx):
         _experimental_use_coverage_metadata_files = ctx.attr._experimental_use_coverage_metadata_files[BuildSettingInfo].value,
         _incompatible_change_rust_test_compilation_output_directory = ctx.attr._incompatible_change_rust_test_compilation_output_directory[IncompatibleFlagInfo].enabled,
         _toolchain_generated_sysroot = ctx.attr._toolchain_generated_sysroot[BuildSettingInfo].value,
+        _incompatible_do_not_include_data_in_compile_data = ctx.attr._incompatible_do_not_include_data_in_compile_data[IncompatibleFlagInfo].enabled,
         _no_std = no_std,
     )
     return [
@@ -905,6 +906,10 @@ rust_toolchain = rule(
                 "This flag is only relevant when used together with --@rules_rust//rust/settings:toolchain_generated_sysroot."
             ),
         ),
+        "_incompatible_do_not_include_data_in_compile_data": attr.label(
+            default = Label("//rust/settings:incompatible_do_not_include_data_in_compile_data"),
+            doc = "Label to a boolean build setting that controls whether to include data files in compile_data.",
+        ),
     },
     toolchains = [
         "@bazel_tools//tools/cpp:toolchain_type",

test/build_env/BUILD.bazel

@@ -9,7 +9,7 @@ package(default_visibility = ["//visibility:public"])
 rust_test(
     name = "conflicting_deps_test",
     srcs = ["tests/manifest_dir.rs"],
-    data = ["src/manifest_dir_file.txt"],
+    compile_data = ["src/manifest_dir_file.txt"],
     edition = "2018",
 )