introduce a path-based discovery mechanism.

Author: davidbarsky

crates/rust-analyzer/src/handlers/request.rs

@@ -2000,8 +2000,15 @@ fn run_rustfmt(
             let workspace = CargoTargetSpec::for_file(&snap, file_id)?;
             let mut cmd = match workspace {
                 Some(spec) => {
-                    let cmd = spec.workspace_root.join(cmd);
-                    process::Command::new(cmd.as_os_str())
+                    // approach: if the command name contains a path seperator, join it with the workspace root.
+                    // however, if the path is absolute, joining will result in the absolute path being preserved.
+                    // as a fallback, rely on $PATH-based discovery.
+                    let cmd_path = if command.contains(std::path::MAIN_SEPARATOR_STR) {
+                        spec.workspace_root.join(cmd).into()
+                    } else {
+                        cmd
+                    };
+                    process::Command::new(cmd_path)
                 }
                 None => process::Command::new(cmd),
             };