Allow xtask::reformat to work without rustup

src/tools/rust-analyzer/xtask/src/codegen.rs

@@ -126,27 +126,35 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     }
 }
 
-fn ensure_rustfmt(sh: &Shell) {
+fn reformat(text: String) -> String {
+    let sh = Shell::new().unwrap();
+    let rustfmt_toml = project_root().join("rustfmt.toml");
     let version = cmd!(sh, "rustup run stable rustfmt --version").read().unwrap_or_default();
+
+    // First try explicitly requesting the stable channel via rustup in case nightly is being used by default,
+    // then plain rustfmt in case rustup isn't being used to manage the compiler (e.g. when using Nix).
+    let mut stdout = if !version.contains("stable") {
+        let version = cmd!(sh, "rustfmt --version").read().unwrap_or_default();
         if !version.contains("stable") {
             panic!(
                 "Failed to run rustfmt from toolchain 'stable'. \
                  Please run `rustup component add rustfmt --toolchain stable` to install it.",
             );
+        } else {
+            cmd!(sh, "rustfmt --config-path {rustfmt_toml} --config fn_single_line=true")
+                .stdin(text)
+                .read()
+                .unwrap()
         }
-}
+    } else {
-
+        cmd!(
-fn reformat(text: String) -> String {
-    let sh = Shell::new().unwrap();
-    ensure_rustfmt(&sh);
-    let rustfmt_toml = project_root().join("rustfmt.toml");
-    let mut stdout = cmd!(
             sh,
             "rustup run stable rustfmt --config-path {rustfmt_toml} --config fn_single_line=true"
         )
         .stdin(text)
         .read()
-    .unwrap();
+        .unwrap()
+    };
     if !stdout.ends_with('\n') {
         stdout.push('\n');
     }