Cannot specify per-target strip_level in MODULE.bazel

[nmattia]

When registering a toolchain with WORKSPACE.bazel once can specify per-target strip levels. For instance:

rust_register_toolchains(
    edition = "2024",
    strip_level = {"x86_64-unknown-linux-gnu": {
        "dbg": "none",
        "fastbuild": "none",
        "opt": "none",
    }},
    versions = ["1.90.0"],
)

This is unfortunately not possible with MODULE.bazel.

It is unfortunately not enough to forward the strip_level parameter:

diff --git a/rust/extensions.bzl b/rust/extensions.bzl
index 99868b0df..1098d65d9 100644
--- a/rust/extensions.bzl
+++ b/rust/extensions.bzl
@@ -115,6 +115,7 @@ def _rust_impl(module_ctx):
                 rust_analyzer_version = toolchain.rust_analyzer_version,
                 sha256s = toolchain.sha256s,
                 extra_target_triples = toolchain.extra_target_triples,
+                strip_level = toolchain.strip_level,
                 urls = toolchain.urls,
                 versions = toolchain.versions,
                 register_toolchains = False,
@@ -219,6 +220,9 @@ _RUST_TOOLCHAIN_TAG = tag_class(
         "rust_analyzer_version": attr.string(
             doc = "The version of Rustc to pair with rust-analyzer.",
         ),
+        "strip_level": attr.string_dict(
+            doc = "Rustc strip levels. For more details see the documentation for `rust_toolchain.strip_level`.",
+        ),
         "target_settings": attr.label_list(
             doc = "A list of `config_settings` that must be satisfied by the target configuration in order for this toolchain to be selected during toolchain resolution.",
         ),

As far as I can tell, a tag class cannot access a dict of dict as an attribute, meaning we can't have 1-to-1 compatibility with a direct call to rust_register_toolchains like in WORKSPACE.bazel.

[nmattia]

Note: for now I'm hard coding the strip level in a patch:

diff --git a/rust/extensions.bzl b/rust/extensions.bzl
index 99868b0df..5932b0760 100644
--- a/rust/extensions.bzl
+++ b/rust/extensions.bzl
@@ -122,6 +122,11 @@ def _rust_impl(module_ctx):
                 toolchain_triples = toolchain_triples,
                 target_settings = [str(v) for v in toolchain.target_settings],
                 extra_toolchain_infos = extra_toolchain_infos,
+                strip_level = {"x86_64-unknown-linux-gnu": {
+                    "dbg": "none",
+                    "fastbuild": "none",
+                    "opt": "none",
+                }},
             )
     metadata_kwargs = {}
     if bazel_features.external_deps.extension_metadata_has_reproducible: