update

lib/smarter_csv/writer.rb

@@ -16,10 +16,9 @@ module SmarterCSV
   # headers : defaults to []
 
   # IMPORTANT NOTES:
-  #  1) Data hashes could contain strings or symbols as keys.
-  #     Make sure to use the correct form when specifying headers manually,
-  #     in combination with the :discover_headers option
-  #  2)
+  #  * Data hashes could contain strings or symbols as keys.
+  #    Make sure to use the correct form when specifying headers manually,
+  #    in combination with the :discover_headers option
 
   class Writer
     def initialize(file_path, options = {})
@@ -63,9 +62,11 @@ def finalize
     private
 
     def process_hash(hash)
-      hash_keys = hash.keys
-      new_keys = hash_keys - @headers
-      @headers.concat(new_keys)
+      if @discover_headers
+        hash_keys = hash.keys
+        new_keys = hash_keys - @headers
+        @headers.concat(new_keys)
+      end
 
       # Reorder the hash to match the current headers order and fill missing fields
       ordered_row = @headers.map { |header| hash[header] || '' }

spec/smarter_csv/writer_spec.rb

@@ -89,6 +89,21 @@
       expect(output).to include("Mike,35,Chicago,,IL\n")
       expect(output).to include("Alex,,,USA,\n")
     end
+
+    context "when discover_headers is turned off" do
+      let(:options) { {discover_headers: false, headers: [:name, :country]} }
+
+      it 'writes the given headers and data correctly' do
+        create_csv_file
+        output = File.read(file_path)
+
+        expect(output).to include("name,country\n")
+        expect(output).to include("John,\n")
+        expect(output).to include("Jane,USA\n")
+        expect(output).to include("Mike,\n")
+        expect(output).to include("Alex,USA\n")
+      end
+    end
   end
 
   context 'when headers are given in advance' do