Add CSV iterator

seq/csvseq/iterate.go

@@ -0,0 +1,24 @@
+package csvseq
+
+import (
+	"encoding/csv"
+	"io"
+	"iter"
+)
+
+// Iterate creates an iterator over the records of the CSV reader. Errors occuring might be csv.ErrFieldCount or
+// parse errors. As Iterate is supposed to consume all the records, the error is never io.EOF.
+func Iterate(reader *csv.Reader) iter.Seq2[[]string, error] {
+	return func(yield func([]string, error) bool) {
+		for {
+			record, err := reader.Read()
+			if err == io.EOF {
+				return
+			}
+
+			if !yield(record, err) {
+				return
+			}
+		}
+	}
+}

seq/csvseq/iterate_example_test.go

@@ -0,0 +1,63 @@
+package csvseq_test
+
+import (
+	"encoding/csv"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/GodsBoss/g/seq/csvseq"
+)
+
+func ExampleIterate_tooFewFields() {
+	raw := strings.Join(
+		[]string{
+			"Foo,Bar,Baz",
+			"a,b",
+			"1,2,3",
+		},
+		"\n",
+	)
+
+	reader := csv.NewReader(strings.NewReader(raw))
+	reader.FieldsPerRecord = 3
+
+	for record, err := range csvseq.Iterate(reader) {
+		if err != nil {
+			fmt.Println("Invalid record " + strings.Join(record, ",") + " - " + err.Error())
+			break
+		}
+	}
+
+	// Output:
+	// Invalid record a,b - record on line 2: wrong number of fields
+}
+
+func ExampleIterate_exhaustion() {
+	raw := strings.Join(
+		[]string{
+			"1,2,3",
+			"a,b,c",
+			"x,y,z",
+		},
+		"\n",
+	)
+
+	reader := csv.NewReader(strings.NewReader(raw))
+
+	var errs error
+
+	for record, err := range csvseq.Iterate(reader) {
+		fmt.Println(record[0])
+		errs = errors.Join(errs, err)
+	}
+
+	if errs != nil {
+		fmt.Println(errs)
+	}
+
+	// Output:
+	// 1
+	// a
+	// x
+}

seq/csvseq/iterate_test.go

@@ -0,0 +1,17 @@
+package csvseq_test
+
+import (
+	"encoding/csv"
+	"strings"
+	"testing"
+
+	"github.com/GodsBoss/g/seq/csvseq"
+)
+
+func TestEmpty(t *testing.T) {
+	iterator := csvseq.Iterate(csv.NewReader(strings.NewReader("")))
+
+	for record, err := range iterator {
+		t.Errorf("expected no iteration, got %v; %v", record, err)
+	}
+}