feat: add option to have gsub_file error if file contents don't change

Author: G-Rath

lib/thor/actions/file_manipulation.rb

@@ -249,7 +249,8 @@ def inject_into_module(path, module_name, *args, &block)
     # path<String>:: path of the file to be changed
     # flag<Regexp|String>:: the regexp or string to be replaced
     # replacement<String>:: the replacement, can be also given as a block
-    # config<Hash>:: give :verbose => false to not log the status, and
+    # config<Hash>:: give :verbose => false to not log the status,
+    #                :error_on_no_change => true to raise an error if the file does not change, and
     #                :force => true, to force the replacement regardless of runner behavior.
     #
     # ==== Example
@@ -270,7 +271,12 @@ def gsub_file(path, flag, *args, &block)
 
       unless options[:pretend]
         content = File.binread(path)
-        content.gsub!(flag, *args, &block)
+        success = content.gsub!(flag, *args, &block)
+
+        if success.nil? && config.fetch(:error_on_no_change, false)
+          raise Thor::Error, "The content of #{path} did not change"
+        end
+
         File.open(path, "wb") { |file| file.write(content) }
       end
     end

spec/actions/file_manipulation_spec.rb

@@ -318,6 +318,26 @@ def file
         it "does not log status if required" do
           expect(action(:gsub_file, file, "__", verbose: false) { |match| match * 2 }).to be_empty
         end
+
+        it "does not care if the file contents did not change" do
+          action :gsub_file, "doc/README", "___start___", "START"
+          expect(File.binread(file)).to eq("__start__\nREADME\n__end__\n")
+        end
+
+        context "with error_on_no_change" do
+          it "replaces the content in the file" do
+            action :gsub_file, "doc/README", "__start__", "START", error_on_no_change: true
+            expect(File.binread(file)).to eq("START\nREADME\n__end__\n")
+          end
+
+          it "raises if the file contents did not change" do
+            expect do
+              action :gsub_file, "doc/README", "___start___", "START", error_on_no_change: true
+            end.to raise_error(Thor::Error)
+
+            expect(File.binread(file)).to eq("__start__\nREADME\n__end__\n")
+          end
+        end
       end
 
       context "with revoke behavior" do