fallback to docker if rustfmt is not installed

rs/README.md

@@ -2,6 +2,10 @@
 
 This folder contains the Rust implementation of the Chain Selectors module.
 
+## Pre-requisites
+
+As part of the code generation, `rustfmt` is used to format the generated code. If you don't have rust toolchain installed, it will run in docker.
+
 ## Build
 
 To build the Chain Selectors module, run the `go generate ./rs` from the root of the project.

rs/genchains_rs.go

@@ -71,17 +71,20 @@ func main() {
 func rustfmt(src []byte) ([]byte, error) {
 	tmpFile := path.Join(os.TempDir(), generatedFileName)
 	if err := os.WriteFile(tmpFile, src, 0644); err != nil {
-		panic(err)
+		return nil, err
 	}
 	defer os.Remove(tmpFile)
 
-	cmd := exec.Command("rustfmt", tmpFile)
-	if err := cmd.Run(); err != nil {
-		panic(err)
+	if err := exec.Command("rustfmt", tmpFile).Run(); err != nil {
+		// if rustfmt is not installed, try to use docker
+		cmd := exec.Command("docker", "run", "--rm", "-v", fmt.Sprintf("%s:/usr/src/app/generated_chains.rs", tmpFile), "-w", "/usr/src/app", "rust:1.82-alpine", "/bin/sh", "-c", "rustup component add rustfmt &>/dev/null && rustfmt generated_chains.rs")
+		if dockerErr := cmd.Run(); dockerErr != nil {
+			return nil, err
+		}
 	}
 	formatted, err := os.ReadFile(tmpFile)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	return formatted, nil