dev_components in rust_register_toolchains doesn't work for all toolchains

[Ngoguey42]

When using rust_register_toolchains, if I use dev_components = True and ios (or android) in extra_target_triples, I get this error during a bazel build:

ERROR: An error occurred during the fetch of repository 'rust_linux_x86_64__aarch64-linux-android__nightly_tools':
   Traceback (most recent call last):
  File "/home/runner/.cache/bazel/_bazel_runner/1fa4b8b6e5f813a6f30004917b5fca72/external/rules_rust/rust/repositories.bzl", line 374, column 31, in _rust_toolchain_tools_repository_impl
    load_rustc_dev_nightly(ctx, target_triple)
  File "/home/runner/.cache/bazel/_bazel_runner/1fa4b8b6e5f813a6f30004917b5fca72/external/rules_rust/rust/private/repository_utils.bzl", line 582, column 24, in load_rustc_dev_nightly
    load_arbitrary_tool(
  File "/home/runner/.cache/bazel/_bazel_runner/1fa4b8b6e5f813a6f30004917b5fca72/external/rules_rust/rust/private/repository_utils.bzl", line 733, column 42, in load_arbitrary_tool
    result = ctx.download_and_extract(
Error in download_and_extract: java.io.IOException: Error downloading [https://static.rust-lang.org/dist/2024-02-22/rustc-dev-nightly-aarch64-linux-android.tar.xz] to /home/runner/.cache/bazel/_bazel_runner/1fa4b8b6e5f813a6f30004917b5fca72/external/rust_linux_x86_64__aarch64-linux-android__nightly_tools/temp11823504000632298494/rustc-dev-nightly-aarch64-linux-android.tar.xz: GET returned 404 Not Found

Here is how I use rust_rules:

http_archive(
    name = "rules_rust",
    integrity = "sha256-ZQGWDD5NoySV0eEAfe0HaaU0yxlcMN6jaqVPnYo/A2E=",
    urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.38.0/rules_rust-v0.38.0.tar.gz"],
)

load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_register_toolchains")

rules_rust_dependencies()

rust_register_toolchains(
    edition = "2021",
    extra_target_triples = [
        "aarch64-apple-ios-sim",
        "aarch64-apple-ios",
        "aarch64-linux-android",
        "x86_64-unknown-linux-gnu",
        "x86_64-apple-ios",
        "wasm32-unknown-unknown",
    ],
    rustfmt_version = "nightly/2024-02-22",
    versions = ["nightly/2024-02-22"],
    dev_components=True,
)

I added some prints in rust/repositories.bzl and I discovered that 49 toolchains were being declared:

rust_darwin_aarch64__aarch64-apple-darwin__nightly
rust_darwin_aarch64__aarch64-apple-ios-sim__nightly
rust_darwin_aarch64__aarch64-apple-ios__nightly
rust_darwin_aarch64__aarch64-linux-android__nightly
rust_darwin_aarch64__x86_64-unknown-linux-gnu__nightly
rust_darwin_aarch64__x86_64-apple-ios__nightly
rust_darwin_aarch64__wasm32-unknown-unknown__nightly
rust_windows_aarch64__aarch64-pc-windows-msvc__nightly
rust_windows_aarch64__aarch64-apple-ios-sim__nightly
rust_windows_aarch64__aarch64-apple-ios__nightly
rust_windows_aarch64__aarch64-linux-android__nightly
rust_windows_aarch64__x86_64-unknown-linux-gnu__nightly
rust_windows_aarch64__x86_64-apple-ios__nightly
rust_windows_aarch64__wasm32-unknown-unknown__nightly
rust_linux_aarch64__aarch64-unknown-linux-gnu__nightly
rust_linux_aarch64__aarch64-apple-ios-sim__nightly
rust_linux_aarch64__aarch64-apple-ios__nightly
rust_linux_aarch64__aarch64-linux-android__nightly
rust_linux_aarch64__x86_64-unknown-linux-gnu__nightly
rust_linux_aarch64__x86_64-apple-ios__nightly
rust_linux_aarch64__wasm32-unknown-unknown__nightly
rust_darwin_x86_64__x86_64-apple-darwin__nightly
rust_darwin_x86_64__aarch64-apple-ios-sim__nightly
rust_darwin_x86_64__aarch64-apple-ios__nightly
rust_darwin_x86_64__aarch64-linux-android__nightly
rust_darwin_x86_64__x86_64-unknown-linux-gnu__nightly
rust_darwin_x86_64__x86_64-apple-ios__nightly
rust_darwin_x86_64__wasm32-unknown-unknown__nightly
rust_windows_x86_64__x86_64-pc-windows-msvc__nightly
rust_windows_x86_64__aarch64-apple-ios-sim__nightly
rust_windows_x86_64__aarch64-apple-ios__nightly
rust_windows_x86_64__aarch64-linux-android__nightly
rust_windows_x86_64__x86_64-unknown-linux-gnu__nightly
rust_windows_x86_64__x86_64-apple-ios__nightly
rust_windows_x86_64__wasm32-unknown-unknown__nightly
rust_freebsd_x86_64__x86_64-unknown-freebsd__nightly
rust_freebsd_x86_64__aarch64-apple-ios-sim__nightly
rust_freebsd_x86_64__aarch64-apple-ios__nightly
rust_freebsd_x86_64__aarch64-linux-android__nightly
rust_freebsd_x86_64__x86_64-unknown-linux-gnu__nightly
rust_freebsd_x86_64__x86_64-apple-ios__nightly
rust_freebsd_x86_64__wasm32-unknown-unknown__nightly
rust_linux_x86_64__x86_64-unknown-linux-gnu__nightly
rust_linux_x86_64__aarch64-apple-ios-sim__nightly
rust_linux_x86_64__aarch64-apple-ios__nightly
rust_linux_x86_64__aarch64-linux-android__nightly
rust_linux_x86_64__x86_64-unknown-linux-gnu__nightly
rust_linux_x86_64__x86_64-apple-ios__nightly
rust_linux_x86_64__wasm32-unknown-unknown__nightly

Which is the cartesian product between my extra_target_triples and rules_rust's DEFAULT_TOOLCHAIN_TRIPLES

I was able to fix my problem by patching the rules_rust http_archive this way:

diff --git a/rust/repositories.bzl b/rust/repositories.bzl
index 610baa79..d50b303d 100644
--- a/rust/repositories.bzl
+++ b/rust/repositories.bzl
@@ -978,13 +978,17 @@ def rust_repository_set(
         elif type(extra_target_triples) == "dict":
             target_compatible_with = extra_target_triples.get(toolchain.target_triple)
 
+        dev_components_for_toolchain = dev_components
+        if '-ios_' in toolchain.name or '-android_' in toolchain.name:
+            dev_components_for_toolchain = False
+
         all_toolchain_names.append(rust_toolchain_repository(
             name = toolchain.name,
             allocator_library = allocator_library,
             global_allocator_library = global_allocator_library,
             auth = auth,
             channel = toolchain.channel.name,
-            dev_components = dev_components,
+            dev_components = dev_components_for_toolchain,
             edition = edition,
             exec_triple = exec_triple,
             extra_exec_rustc_flags = extra_exec_rustc_flags,

Is there a way for me to avoid that problem without relying on a rules_rust patch?