From d5a9d8c63faafcaf8639298c6ea379bae45e9a24 Mon Sep 17 00:00:00 2001
From: UebelAndre <github@uebelandre.com>
Date: Thu, 12 Aug 2021 10:09:45 -0700
Subject: [PATCH] Updated `//tools/rustfmt` to dynamically work within
 `rules_rust` itself (#883)

---
 tools/rustfmt/BUILD.bazel       |  9 ++++++++-
 tools/rustfmt/rustfmt_utils.bzl | 18 ++++++++++++++++++
 tools/rustfmt/srcs/main.rs      |  9 ++++++---
 3 files changed, 32 insertions(+), 4 deletions(-)
 create mode 100644 tools/rustfmt/rustfmt_utils.bzl

diff --git a/tools/rustfmt/BUILD.bazel b/tools/rustfmt/BUILD.bazel
index 93abad4398..135ec025d9 100644
--- a/tools/rustfmt/BUILD.bazel
+++ b/tools/rustfmt/BUILD.bazel
@@ -1,8 +1,12 @@
 load("//rust:defs.bzl", "rust_binary", "rust_clippy", "rust_library")
+load(":rustfmt_utils.bzl", "aspect_repository")
 
 package(default_visibility = ["//visibility:public"])
 
-exports_files(["rustfmt.toml"])
+exports_files([
+    "rustfmt.toml",
+    "rustfmt_utils.bzl",
+])
 
 rust_library(
     name = "rustfmt_lib",
@@ -30,6 +34,9 @@ rust_binary(
         "//:rustfmt.toml",
     ],
     edition = "2018",
+    rustc_env = {
+        "ASPECT_REPOSITORY": aspect_repository(),
+    },
     deps = [
         ":rustfmt_lib",
         "//util/label",
diff --git a/tools/rustfmt/rustfmt_utils.bzl b/tools/rustfmt/rustfmt_utils.bzl
new file mode 100644
index 0000000000..b1fb391058
--- /dev/null
+++ b/tools/rustfmt/rustfmt_utils.bzl
@@ -0,0 +1,18 @@
+"""A helper module for the `@rules_rust//tools/rustfmt` package"""
+
+def aspect_repository():
+    """Determines the repository name to use for the `rustfmt_manifest` aspect in `rustfmt` binaries.
+
+    The `//tools/rustfmt` target has a hard coded `--aspects` command built into it.
+    This function is designed to allow for this aspect to be updated to work within
+    the `rules_rust` repository itself since aspects do not work if the repository name
+    is explicitly set.
+
+    https://github.com/bazelbuild/rules_rust/issues/749
+
+    Returns:
+        str: The string to use for the `rustfmt_aspect` repository
+    """
+    if native.repository_name() == "@":
+        return ""
+    return native.repository_name()
diff --git a/tools/rustfmt/srcs/main.rs b/tools/rustfmt/srcs/main.rs
index f1d95c65b8..eb6d0b13f8 100644
--- a/tools/rustfmt/srcs/main.rs
+++ b/tools/rustfmt/srcs/main.rs
@@ -75,9 +75,12 @@ fn query_rustfmt_targets(options: &Config) -> Vec<String> {
 /// arguments to use when formatting the sources of those targets.
 fn generate_rustfmt_target_manifests(options: &Config, targets: &[String]) {
     let build_args = vec![
-        "build",
-        "--aspects=@rules_rust//rust:defs.bzl%rustfmt_aspect",
-        "--output_groups=rustfmt_manifest",
+        "build".to_owned(),
+        format!(
+            "--aspects={}//rust:defs.bzl%rustfmt_aspect",
+            env!("ASPECT_REPOSITORY")
+        ),
+        "--output_groups=rustfmt_manifest".to_owned(),
     ];
 
     let child = Command::new(&options.bazel)