1 files changed, 45 insertions, 7 deletions
diff --git a/skate/map.go b/skate/map.go
index 9d3c98d..d6e37be 100644
--- a/skate/map.go
+++ b/skate/map.go
@@ -25,10 +25,11 @@ type TitleDoc struct {
 }
 
 // PartialDoc for docs, that do not have DOI or title. E.g. we found 49701699
-// (NCVY), 36401044 (NCVYU), 29668363 (NCUY), and so on.
+// (NCVY), 36401044 (NCVYU), 29668363 (NCUY), and so on. Some examples: XXX
 type PartialDoc struct {
 	ContainerName string `json:"container_name"`
 	Contribs      []struct {
+		// XXX: Need a way to sensibly compare sets of author names.
 		RawName string `json:"raw_name"`
 	} `json:"contribs"`
 	Volume       string `json:"volume"`
@@ -40,17 +41,29 @@ type PartialDoc struct {
 // doc). We want fields, but we do not want to bake in TSV into each function.
 type Mapper func([]byte) ([][]byte, error)
 
-// AsTSV serializes the result of a field mapper as TSV. This is a slim adapter,
-// e.g. to parallel.Processor, which expects this function signature.
+// AsTSV serializes the result of a field mapper as TSV. This is a slim
+// adapter, e.g. to parallel.Processor, which expects this function signature.
+// A newline will be appended, if not there already.
 func (f Mapper) AsTSV(p []byte) ([]byte, error) {
-	fields, err := f(p)
-	if err != nil {
+	var (
+		fields [][]byte
+		err    error
+		b      []byte
+	)
+	if fields, err = f(p); err != nil {
 		return nil, err
 	}
-	return bytes.Join(fields, bTab), nil
+	if len(fields) == 0 {
+		return nil, nil
+	}
+	b = bytes.Join(fields, bTab)
+	if len(b) > 0 && !bytes.HasSuffix(b, bNewline) {
+		b = append(b, bNewline...)
+	}
+	return b, nil
 }
 
-// WithPrefix adds a given prefix to the first element.
+// WithPrefix is a "mapper middleware", adding a given prefix to the first field.
 func WithPrefix(f Mapper, prefix string) Mapper {
 	return func(p []byte) ([][]byte, error) {
 		fields, err := f(p)
@@ -65,6 +78,31 @@ func WithPrefix(f Mapper, prefix string) Mapper {
 	}
 }
 
+// WithBestEffort will not fail on an error.
+func WithBestEffort(f Mapper) Mapper {
+	return func(p []byte) ([][]byte, error) {
+		if fields, err := f(p); err != nil {
+			return nil, nil
+		} else {
+			return fields, err
+		}
+	}
+}
+
+// WithSkipOnEmpty ignores results where the value at a given field is empty.
+func WithSkipOnEmpty(f Mapper, index int) Mapper {
+	return func(p []byte) ([][]byte, error) {
+		fields, err := f(p)
+		if err != nil {
+			return nil, err
+		}
+		if index < len(fields) && len(fields[index]) == 0 {
+			return nil, nil
+		}
+		return fields, err
+	}
+}
+
 // NameOf returns name of value, e.g. the name of a function.
 func NameOf(f interface{}) string {
 	v := reflect.ValueOf(f)