Allow rust toolchain repositories from custom repo rules

[ikalchev]

If I use some non-standard packaging system and thus have a custom repo rules that pull rust binaries (rustc, cargo), I would like to be able to configure the rust_toolchain_repository_proxy (or otherwise) to use this other repo rule.

My current workaround is to:

1. Define a rust_toolchain which uses the artefacts from the custom repo rule. This is needed for using rust in bazel outside of the crate_universe (i.e. not important to this issue).
2. Patch crate_universe to accept a mapping from tool to path.
3. Use crate_universe as:

crate_univers(
        ...
        rust_toolchain_repository_template = "custom repo rule label",
        rust_toolchain_repository_tool_path = {
            "cargo": "path to cargo within custom repo",
            "rustc": "path to cargo within custom repo",
        },
        ...

[illicitonion]

If you can't make it so that cargo is at //:bin/cargo in your repository, and rustc is at //:bin/rustc in your repository (which would be ideal), I'd be happy to review a patch which made the paths to these tools within the repository configurable :) I imagine it should be a simple change to put together (as it sounds like you already have done), adding an attribute or two here

rules_rust/crate_universe/defs.bzl

Line 221 in 53b1de6

"rust_toolchain_repository_template": attr.string(

and consuming them here

rules_rust/crate_universe/private/util.bzl

Lines 137 to 138 in 53b1de6

	cargo_path = repository_ctx.path(Label("@{}{}".format(rust_toolchain_repository, "//:bin/cargo" + extension)))
	rustc_path = repository_ctx.path(Label("@{}{}".format(rust_toolchain_repository, "//:bin/rustc" + extension)))

[ikalchev]

Here is my diff. Let me know if you would like a PR.

diff --git a/crate_universe/defs.bzl b/crate_universe/defs.bzl
index ea9b5f2..2c85d08 100644
--- a/crate_universe/defs.bzl
+++ b/crate_universe/defs.bzl
@@ -157,7 +157,7 @@ __WARNING__: This rule experimental and subject to change without warning.
 Environment Variables:
 - `REPIN`: Re-pin the lockfile if set (useful for repinning deps from multiple rulesets).
 - `RULES_RUST_REPIN`: Re-pin the lockfile if set (useful for only repinning Rust deps).
-- `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE`: Override URL to use to download resolver binary 
+- `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE`: Override URL to use to download resolver binary
     - for local paths use a `file://` URL.
 - `RULES_RUST_CRATE_UNIVERSE_RESOLVER_URL_OVERRIDE_SHA256`: An optional sha256 value for the binary at the override url location.
 """,
@@ -226,6 +226,13 @@ Dict of registry_name: index_url.
             ),
             default = "rust_{system}_{arch}",
         ),
+        "rust_toolchain_repository_tool_path": attr.string_dict(
+            doc = "The relative path of the tools in the repository",
+            default = {
+                "cargo": "bin/cargo",
+                "rustc": "bin/rustc"
+            }
+        ),
         "sha256s": attr.string_dict(
             doc = "The sha256 checksum of the desired rust artifacts",
         ),
diff --git a/crate_universe/private/util.bzl b/crate_universe/private/util.bzl
index ca64116..1a43ca6 100644
--- a/crate_universe/private/util.bzl
+++ b/crate_universe/private/util.bzl
@@ -134,8 +134,13 @@ def get_cargo_and_rustc(repository_ctx, host_triple):
     rust_toolchain_repository = rust_toolchain_repository.replace("{triple}", host_triple)
     rust_toolchain_repository = rust_toolchain_repository.replace("{arch}", arch)
 
-    cargo_path = repository_ctx.path(Label("@{}{}".format(rust_toolchain_repository, "//:bin/cargo" + extension)))
-    rustc_path = repository_ctx.path(Label("@{}{}".format(rust_toolchain_repository, "//:bin/rustc" + extension)))
+    tool_path = repository_ctx.attr.rust_toolchain_repository_tool_path
+    cargo_path = repository_ctx.path(Label("@{}//:{}{}".format(
+        rust_toolchain_repository, tool_path["cargo"], extension
+    )))
+    rustc_path = repository_ctx.path(Label("@{}//:{}{}".format(
+        rust_toolchain_repository, tool_path["rustc"], extension
+    )))
 
     return struct(
         cargo = cargo_path,

[illicitonion]

A PR would be great if you wouldn't mind!

Also, let's include the : in the values so that folks can have package structure if they want.

Thanks!