Use FilterLine Instead of FilterScan

Author: mahadzaryab1

script.go

@@ -668,20 +668,20 @@ func (p *Pipe) Hash(hasher hash.Hash) (string, error) {
 
 // HashSums reads paths from the pipe, one per line, and produces the
 // hex-encoded hash of each corresponding file based on the provided hasher,
-// one per line. Any files that cannot be opened or read will be ignored.
+// one per line. Any files that cannot be opened or read will print an empty line.
 // To perform hashing on the contents of the pipe, see [Pipe.Hash].
 func (p *Pipe) HashSums(hasher hash.Hash) *Pipe {
-	return p.FilterScan(func(line string, w io.Writer) {
+	return p.FilterLine(func(line string) string {
 		f, err := os.Open(line)
 		if err != nil {
-			return // skip unopenable files
+			return "" // skip unopenable files
 		}
 		defer f.Close()
 		_, err = io.Copy(hasher, f)
 		if err != nil {
-			return // skip unreadable files
+			return "" // skip unreadable files
 		}
-		fmt.Fprintln(w, hex.EncodeToString(hasher.Sum(nil)))
+		return hex.EncodeToString(hasher.Sum(nil))
 	})
 }
 

script_test.go

@@ -2100,6 +2100,17 @@ func TestHashSums_OutputsCorrectHashForEachSpecifiedFile(t *testing.T) {
 	}
 }
 
+func TestHashSums_OutputsEmptyLineForFileThatCannotBeHashed(t *testing.T) {
+	got, err := script.Echo("file_does_not_exist.txt").HashSums(sha256.New()).String()
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "\n"
+	if got != want {
+		t.Errorf("want %q, got %q", want, got)
+	}
+}
+
 func TestHash_ReturnsErrorGivenReadErrorOnPipe(t *testing.T) {
 	t.Parallel()
 	brokenReader := iotest.ErrReader(errors.New("oh no"))