Add header support to tableprinter

pkg/tableprinter/table.go

@@ -15,6 +15,7 @@ import (
 type fieldOption func(*tableField)
 
 type TablePrinter interface {
+	AddHeaders([]string, ...fieldOption)
 	AddField(string, ...fieldOption)
 	EndRow()
 	Render() error
@@ -47,6 +48,7 @@ func New(w io.Writer, isTTY bool, maxWidth int) TablePrinter {
 			maxWidth: maxWidth,
 		}
 	}
+
 	return &tsvTablePrinter{
 		out: w,
 	}
@@ -59,9 +61,22 @@ type tableField struct {
 }
 
 type ttyTablePrinter struct {
-	out      io.Writer
-	maxWidth int
-	rows     [][]tableField
+	out        io.Writer
+	maxWidth   int
+	hasHeaders bool
+	rows       [][]tableField
+}
+
+func (t *ttyTablePrinter) AddHeaders(headers []string, opts ...fieldOption) {
+	if t.hasHeaders {
+		return
+	}
+
+	t.hasHeaders = true
+	for _, header := range headers {
+		t.AddField(header, opts...)
+	}
+	t.EndRow()
 }
 
 func (t *ttyTablePrinter) AddField(s string, opts ...fieldOption) {
@@ -92,7 +107,7 @@ func (t *ttyTablePrinter) Render() error {
 	numCols := len(t.rows[0])
 	colWidths := t.calculateColumnWidths(len(delim))
 
-	for _, row := range t.rows {
+	for i, row := range t.rows {
 		for col, field := range row {
 			if col > 0 {
 				_, err := fmt.Fprint(t.out, delim)
@@ -104,7 +119,7 @@ func (t *ttyTablePrinter) Render() error {
 			if field.truncateFunc != nil {
 				truncVal = field.truncateFunc(colWidths[col], field.text)
 			}
-			if col < numCols-1 {
+			if col < numCols-1 || i == 0 && t.hasHeaders {
 				// pad value with spaces on the right
 				if padWidth := colWidths[col] - text.DisplayWidth(field.text); padWidth > 0 {
 					truncVal += strings.Repeat(" ", padWidth)
@@ -213,6 +228,8 @@ type tsvTablePrinter struct {
 	currentCol int
 }
 
+func (t *tsvTablePrinter) AddHeaders(_ []string, _ ...fieldOption) {}
+
 func (t *tsvTablePrinter) AddField(text string, opts ...fieldOption) {
 	if t.currentCol > 0 {
 		fmt.Fprint(t.out, "\t")

pkg/tableprinter/table_test.go

@@ -2,9 +2,12 @@ package tableprinter
 
 import (
 	"bytes"
+	"fmt"
 	"log"
 	"os"
 	"testing"
+
+	"github.com/MakeNowJust/heredoc"
 )
 
 func ExampleTablePrinter() {
@@ -74,6 +77,35 @@ func Test_ttyTablePrinter_WithTruncate(t *testing.T) {
 	}
 }
 
+func Test_ttyTablePrinter_AddHeaders(t *testing.T) {
+	buf := bytes.Buffer{}
+	tp := New(&buf, true, 80)
+
+	tp.AddHeaders([]string{"ONE", "TWO", "THREE"}, WithColor(func(s string) string {
+		return fmt.Sprintf("\x1b[4m%s\x1b[m", s)
+	}))
+	tp.AddHeaders([]string{"SHOULD", "NOT", "EXIST"})
+
+	tp.AddField("hello")
+	tp.AddField("beautiful")
+	tp.AddField("people")
+	tp.EndRow()
+
+	err := tp.Render()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	// Assert the last column header is padded to support underlines, background styles, etc.
+	expected := heredoc.Docf(`
+		%[1]s[4mONE  %[1]s[m  %[1]s[4mTWO      %[1]s[m  %[1]s[4mTHREE %[1]s[m
+		hello  beautiful  people
+	`, "\x1b")
+	if buf.String() != expected {
+		t.Errorf("expected: %q, got: %q", expected, buf.String())
+	}
+}
+
 func Test_tsvTablePrinter(t *testing.T) {
 	buf := bytes.Buffer{}
 	tp := New(&buf, false, 0)