fix: Prevent unexpected newline in output for empty files (#35)

* fix: Prevent unexpected newline in output for empty files

Modified ReadContentConcurrently and AggregateContent functions in reader package to handle empty content scenarios gracefully. ReadContentConcurrently now checks for empty content before appending to results, ensuring only valid content is processed. AggregateContent skips appending newline separators for empty content, addressing the issue where empty files would erroneously contribute newlines to the final output.

- [x] Review the unit tests for ParseContent to ensure they cover the case of empty file input.
- [x] Consider adding a test specifically for this scenario to prevent regressions in the future.

Closes #31

* test(reader): Prevent regression with empty files

Updated tests in reader_test.go to include checks for handling empty files in ParseContent function of reader package. Added tests to verify that ParseContent correctly returns an empty string when provided with an empty file path and a newline character string. This ensures consistent behavior and addresses potential issues highlighted in #31.

cli/reader/reader.go

@@ -58,9 +58,12 @@ func ReadContentConcurrently(readers []ContentReader) ([]string, error) {
 				errChan <- err // Send error to channel
 				return
 			}
-			mu.Lock()
-			results[i] = content // Safely write to results slice
-			mu.Unlock()
+
+			if content != "" { // Check for empty content before writing to results
+				mu.Lock()
+				results[i] = content // Safely write to results slice
+				mu.Unlock()
+			}
 		}(i, reader)
 	}
 
@@ -79,7 +82,9 @@ func ReadContentConcurrently(readers []ContentReader) ([]string, error) {
 func AggregateContent(results []string) string {
 	var sb strings.Builder
 	for _, content := range results {
-		sb.WriteString(content + "\n")
+		if content != "" { // Ensure non-empty content is aggregated
+			sb.WriteString(content + "\n")
+		}
 	}
 	return sb.String()
 }

tests/reader/reader_test.go

@@ -104,7 +104,8 @@ func TestParseContent(t *testing.T) {
 		}
 
 		// Expected result when parsing an empty file
-		expected := "\n"
+		emptyString := ""
+		newlineString := "\n"
 
 		// Create a FileContentReader for the empty file
 		testReader := reader.FileContentReader{FilePath: emptyFile.Name()}
@@ -115,9 +116,12 @@ func TestParseContent(t *testing.T) {
 			t.Fatalf("Expected no error, got: %v", err)
 		}
 
-		// Verify the actual output matches the expected output
-		if actual != expected {
-			t.Errorf("Expected %s but got %s", expected, actual)
+		if actual != emptyString {
+			t.Error("When given an empty file returned something else.")
+		}
+
+		if actual == newlineString {
+			t.Error("When given empty file returned one with newline '\\n' character. See: https://github.com/supitsdu/clipper/issues/31#issue-2379691170")
 		}
 	})