Fix symlink regression

lib/react_on_rails/assets_precompile.rb

@@ -26,11 +26,7 @@ def symlink_file(target, symlink)
       target_exists = File.exist?(target_path)
       raise SymlinkTargetDoesNotExistException, "Target Path was: #{target_path}" unless target_exists
 
-      # File.exist?(symlink_path) will check the file the sym is pointing to is existing
-      # File.lstat(symlink_path).symlink? confirms that this is a symlink
-      valid_symlink_already_exists = File.exist?(symlink_path) && File.lstat(symlink_path).symlink?
-
-      if valid_symlink_already_exists
+      if symlink_and_points_to_existing_file?(symlink_path)
         puts "React On Rails: Digested version of #{symlink} already exists indicating #{target} did not change."
         return
       end
@@ -120,7 +116,15 @@ def clobber
 
     private
 
+    def symlink_and_points_to_existing_file?(symlink_path)
+      # File.exist?(symlink_path) will check the file the sym is pointing to is existing
+      # File.lstat(symlink_path).symlink? confirms that this is a symlink
+      File.exist?(symlink_path) && File.lstat(symlink_path).symlink?
+    end
+
     def file_or_symlink_exists_at_path?(path)
+      # We use lstat and not stat, we we don't want to visit the file that the symlink maybe
+      # pointing to. We can't use File.exist?, as that would check the file pointed at by the symlink.
       File.lstat(path)
       true
     rescue

spec/react_on_rails/assets_precompile_spec.rb

@@ -62,6 +62,48 @@ module ReactOnRails
           end.to raise_exception(AssetsPrecompile::SymlinkTargetDoesNotExistException)
         end
       end
+
+      it "creates a proper symlink when a file exists at destination" do
+        filename = File.basename(Tempfile.new("tempfile", assets_path))
+        existing_filename = File.basename(Tempfile.new("tempfile", assets_path))
+        digest_filename = existing_filename
+
+        AssetsPrecompile.new(assets_path: assets_path).symlink_file(filename, digest_filename)
+        expect(assets_path.join(digest_filename).lstat.symlink?).to be true
+        expect(File.identical?(assets_path.join(filename),
+                               assets_path.join(digest_filename))).to be true
+      end
+
+      it "creates a proper symlink when a symlink file exists at destination" do
+        filename = File.basename(Tempfile.new("tempfile", assets_path))
+        existing_filename = File.basename(Tempfile.new("tempfile", assets_path))
+        digest_file = Tempfile.new("tempfile", assets_path)
+        digest_filename = File.basename(digest_file)
+        File.delete(digest_file)
+        File.symlink(existing_filename, digest_filename)
+
+        AssetsPrecompile.new(assets_path: assets_path).symlink_file(filename, digest_filename)
+        expect(assets_path.join(digest_filename).lstat.symlink?).to be true
+        expect(File.identical?(assets_path.join(filename),
+                               assets_path.join(digest_filename))).to be true
+        File.delete(digest_filename)
+      end
+
+      it "creates a proper symlink when an invalid symlink exists at destination" do
+        filename = File.basename(Tempfile.new("tempfile", assets_path))
+        existing_file = Tempfile.new("tempfile", assets_path)
+        existing_filename = File.basename(existing_file)
+        digest_file = Tempfile.new("tempfile", assets_path)
+        digest_filename = File.basename(digest_file)
+        File.symlink(existing_filename, digest_filename)
+        File.delete(existing_file) # now digest_filename is an invalid link
+
+        AssetsPrecompile.new(assets_path: assets_path).symlink_file(filename, digest_filename)
+        expect(assets_path.join(digest_filename).lstat.symlink?).to be true
+        expect(File.identical?(assets_path.join(filename),
+                               assets_path.join(digest_filename))).to be true
+        File.delete(digest_filename)
+      end
     end
 
     describe "symlink_non_digested_assets" do