Preserve caller paths when inserting a pipeline

CHANGELOG.md

@@ -1,5 +1,7 @@
 **Master**
 
+- Preserve caller paths when inserting a pipeline. [Oskar Eichler](https://github.com/OskarEichler)
+
 Get upgrade notes from Sprockets 3.x to 4.x at https://github.com/rails/sprockets/blob/master/UPGRADING.md
 
 # 4.4.1

README.md

@@ -714,3 +714,5 @@ Please see the [CHANGELOG](https://github.com/rails/sprockets/tree/master/CHANGE
 
 ## License
 Sprockets is released under the [MIT License](MIT-LICENSE).
+
+Inserting a pipeline leaves the caller path unchanged and accepts frozen paths.

lib/sprockets/path_utils.rb

@@ -147,7 +147,7 @@ def join(base, path)
     # Returns string path with pipeline parsed in
     def set_pipeline(path, mime_exts, pipeline_exts, pipeline)
       extension, _ = match_path_extname(path, mime_exts)
-      path.chomp!(extension)
+      path = path.chomp(extension)
       pipeline_old, _ = match_path_extname(path, pipeline_exts)
       path.chomp!(pipeline_old)