Initial table template functions

Resolves cli#3488

pkg/export/table.go

@@ -0,0 +1,49 @@
+package export
+
+import (
+	"fmt"
+	"io"
+	"strings"
+	"text/tabwriter"
+)
+
+type tableFormatter struct {
+	current *table
+	writer  io.Writer
+}
+
+type table struct {
+	tabwriter *tabwriter.Writer
+}
+
+// Initialize a new tabwriter.
+func (f *tableFormatter) Table() string {
+	f.current = &table{
+		// Write directly to the same writer as template execution
+		// since writing to a buffer isn't getting flushed properly.
+		tabwriter: tabwriter.NewWriter(f.writer, 0, 1, 1, ' ', 0),
+	}
+	return ""
+}
+
+// Write a row of string fields. Formatting must be performed before passing to Row.
+func (f *tableFormatter) Row(fields ...string) (string, error) {
+	if f.current == nil {
+		return "", fmt.Errorf("no current table. use '{{table}}' to start a table")
+	}
+	row := strings.Join(fields, "\t")
+	if _, err := f.current.tabwriter.Write([]byte(row + "\n")); err != nil {
+		return "", fmt.Errorf("failed to write row: %v", err)
+	}
+	return "", nil
+}
+
+// End the table and flush rows, adjusting for columns' widths using elastic tabstops.
+func (f *tableFormatter) EndTable() (string, error) {
+	if f.current == nil {
+		return "", fmt.Errorf("no current table. use '{{table}}' to start a table")
+	}
+	f.current.tabwriter.Flush()
+	f.current = nil
+	return "", nil
+}

pkg/export/table_test.go

@@ -0,0 +1,26 @@
+package export
+
+import (
+	"strings"
+	"testing"
+)
+
+func Test_Row_withoutTable(t *testing.T) {
+	formatter := &tableFormatter{
+		current: nil,
+		writer:  &strings.Builder{},
+	}
+	if _, err := formatter.Row("col"); err == nil {
+		t.Errorf("expected error, got nil")
+	}
+}
+
+func Test_EndTable_withoutTable(t *testing.T) {
+	formatter := &tableFormatter{
+		current: nil,
+		writer:  &strings.Builder{},
+	}
+	if _, err := formatter.EndTable(); err == nil {
+		t.Errorf("expected error, got nil")
+	}
+}

pkg/export/template.go

@@ -16,9 +16,13 @@ import (
 	"github.com/mgutz/ansi"
 )
 
-func parseTemplate(tpl string, colorEnabled bool) (*template.Template, error) {
+func parseTemplate(w io.Writer, tpl string, colorEnabled bool) (*template.Template, error) {
 	now := time.Now()
 
+	tableFormatter := &tableFormatter{
+		current: nil,
+		writer:  w,
+	}
 	templateFuncs := map[string]interface{}{
 		"color":     templateColor,
 		"autocolor": templateColor,
@@ -41,6 +45,10 @@ func parseTemplate(tpl string, colorEnabled bool) (*template.Template, error) {
 		"ellipsis": templateEllipsis,
 		"join":     templateJoin,
 		"pluck":    templatePluck,
+
+		"table":    tableFormatter.Table,
+		"row":      tableFormatter.Row,
+		"endTable": tableFormatter.EndTable,
 	}
 
 	if !colorEnabled {
@@ -53,7 +61,7 @@ func parseTemplate(tpl string, colorEnabled bool) (*template.Template, error) {
 }
 
 func ExecuteTemplate(w io.Writer, input io.Reader, templateStr string, colorEnabled bool) error {
-	t, err := parseTemplate(templateStr, colorEnabled)
+	t, err := parseTemplate(w, templateStr, colorEnabled)
 	if err != nil {
 		return err
 	}

pkg/export/template_test.go

@@ -156,6 +156,19 @@ func Test_executeTemplate(t *testing.T) {
 			},
 			wantW: "bug\nfe...\nchore\n",
 		},
+		{
+			name: "table",
+			args: args{
+				json: strings.NewReader(heredoc.Doc(`[
+					{"number": 1, "title": "One"},
+					{"number": 20, "title": "Twenty"},
+					{"number": 3000, "title": "Three thousand"}
+				]`)),
+				template: `{{table}}{{range .}}{{row (.number | printf "#%v") .title}}{{end}}{{endTable}}`,
+				colorize: false,
+			},
+			wantW: "#1    One\n#20   Twenty\n#3000 Three thousand\n",
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {