Add an option to edit the fullPackageName value for the hashing logic (#23)

* add an option to edit the fullPackageName value for the hashing logic

* simplify implementation

Author: nikolasmatt

templates/hash/functions.go

@@ -11,6 +11,8 @@ import (
 	pgsgo "github.com/lyft/protoc-gen-star/lang/go"
 )
 
+const TRANSFORM_PACKAGE_FOR_HASH_PARAMETER_NAME = "transform_package_for_hash"
+
 func register(tpl *template.Template, params pgs.Parameters) {
 	fns := goSharedFuncs{
 		Context: pgsgo.InitContext(params),
@@ -52,8 +54,24 @@ func (fns goSharedFuncs) fieldName(field pgs.Field) string {
 	return fmt.Sprintf("%s", fns.Name(field))
 }
 
+// fullPackageName constructs and returns the full package name of a message as a string.
+// If the parameter transform_package_for_hash is set, using the format "old=new", the function will
+// replace all instances of "old" with "new" in the full package name before returning the new value.
+// If the parameter transform_package_for_hash does not have a empty or valid value, the function will panic.
 func (fns goSharedFuncs) fullPackageName(msg pgs.Message) string {
-	return fmt.Sprintf("%s.%s.%s", msg.Package().ProtoName(), fns.ImportPath(msg), fns.Name(msg))
+	fullPackageName := fmt.Sprintf("%s.%s.%s", msg.Package().ProtoName(), fns.ImportPath(msg), fns.Name(msg))
+	transformPackageForHash := fns.Params().Str(TRANSFORM_PACKAGE_FOR_HASH_PARAMETER_NAME)
+	if transformPackageForHash == "" {
+		return fullPackageName
+	}
+
+	replaceParts := strings.Split(transformPackageForHash, "=")
+	if len(replaceParts) != 2 {
+		// If the valud in the parameter is not in the format "old=new", the process should fail
+		panic(fmt.Sprintf("Invalid transform string: %s", transformPackageForHash))
+	}
+
+	return strings.ReplaceAll(fullPackageName, replaceParts[0], replaceParts[1])
 }
 
 func (fns goSharedFuncs) lookup(f pgs.Field, name string) string {