cargo_build_script should not forward data to build.rs rust_binary

[ashi009]

When embedding generated targets in the cargo_build_script's data attribute, it will be embedded as runfiles for the actual script's rust_binary target. As cargo_build_script performs config transition for the script attribute, all the data dependencies will be built again using the exec configuration. This is incorrect, as the data required by the build.rs should be built into the target configuration to be linked correctly when cross-compiling.

Taking glib-sys as an example:

rust_library(
    name = "glib_sys",
    deps = [
        "@crate_index__glib-sys-0.18.1//:build_script_build",
        "@crate_index__libc-0.2.155//:libc",
        "@glib//:glib",
    ],
	...
)

cargo_build_script(
    name = "glib-sys_bs",
    crate_name = "build_script_build",
    crate_root = "build.rs",
    data = glob(
        allow_empty = True,
        include = ["**"],
        exclude = [
            "**/* *",
            ".tmp_git_root/**/*",
            "BUILD",
            "BUILD.bazel",
            "WORKSPACE",
            "WORKSPACE.bazel",
        ],
    ) + [
        "@glib//:glib", # <-- target cfg
    ],
    deps = [
        "@crate_index__system-deps-6.2.2//:system_deps",
    ],
	...
)

which expands to:

cargo_build_script(
    name = "glib-sys_bs",
    data = [
		...
        "@glib//:glib",
    ],
    deps = ["@crate_index__system-deps-6.2.2//:system_deps"],
    script = "@crate_index__glib-sys-0.18.1//:glib-sys_bs_",
	...
)

rust_binary(
    name = "glib-sys_bs_",
    compile_data = [],
    crate_features = [],
    crate_name = "build_script_build",
    crate_root = "@crate_index__glib-sys-0.18.1//:build.rs",
    data = [
		...
        "@glib//:glib", # <-- exec cfg
    ],
    deps = ["@crate_index__system-deps-6.2.2//:system_deps"],
	...
)

[ashi009]

@UebelAndre Is this fixed by #2858?

My fix was to avoid using runfiles, but to run build script at the crate root.

 cargo/private/cargo_build_script.bzl         | 2 +-
 cargo/private/cargo_build_script_wrapper.bzl | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/cargo/private/cargo_build_script.bzl b/cargo/private/cargo_build_script.bzl
index 6524ce2..588e2cc 100644
--- a/cargo/private/cargo_build_script.bzl
+++ b/cargo/private/cargo_build_script.bzl
@@ -144,7 +144,7 @@ def _cargo_build_script_impl(ctx):
     flags_out = ctx.actions.declare_file(ctx.label.name + ".flags")
     link_flags = ctx.actions.declare_file(ctx.label.name + ".linkflags")
     link_search_paths = ctx.actions.declare_file(ctx.label.name + ".linksearchpaths")  # rustc-link-search, propagated from transitive dependencies
-    manifest_dir = "%s.runfiles/%s/%s" % (script.path, ctx.label.workspace_name or ctx.workspace_name, ctx.label.package)
+    manifest_dir = "%s/%s" % (ctx.label.workspace_root, ctx.label.package)
     compilation_mode_opt_level = get_compilation_mode_opts(ctx, toolchain).opt_level
 
     streams = struct(
diff --git a/cargo/private/cargo_build_script_wrapper.bzl b/cargo/private/cargo_build_script_wrapper.bzl
index 1860e61..8549499 100644
--- a/cargo/private/cargo_build_script_wrapper.bzl
+++ b/cargo/private/cargo_build_script_wrapper.bzl
@@ -154,7 +154,6 @@ def cargo_build_script(
         crate_features = crate_features,
         deps = deps,
         proc_macro_deps = proc_macro_deps,
-        data = data,
         compile_data = compile_data,
         rustc_env = rustc_env,
         rustc_env_files = rustc_env_files,

[UebelAndre]

This should be fixed by #2826. Closing out unless someone finds it's still an issue!