Omit empty lines on template printer slice objects. (#142)

pkg/genericcli/printers/template.go

@@ -9,20 +9,22 @@ import (
 	"reflect"
 	"text/template"
 
-	"github.com/go-task/slim-sprig/v3"
+	sprig "github.com/go-task/slim-sprig/v3"
 )
 
 // TemplatePrinter prints data with a given template
 type TemplatePrinter struct {
-	out  io.Writer
-	text string
-	t    *template.Template
+	out       io.Writer
+	text      string
+	t         *template.Template
+	omitEmpty bool
 }
 
 func NewTemplatePrinter(template string) *TemplatePrinter {
 	return &TemplatePrinter{
-		out:  os.Stdout,
-		text: template,
+		out:       os.Stdout,
+		text:      template,
+		omitEmpty: true,
 	}
 }
 
@@ -36,6 +38,11 @@ func (p *TemplatePrinter) WithTemplate(t *template.Template) *TemplatePrinter {
 	return p
 }
 
+func (p *TemplatePrinter) WithoutOmitEmptyLines() *TemplatePrinter {
+	p.omitEmpty = false
+	return p
+}
+
 func (p *TemplatePrinter) Print(data any) error {
 	if p.t == nil {
 		var err error
@@ -91,7 +98,9 @@ func (p *TemplatePrinter) print(data any) error {
 		return fmt.Errorf("unable to render template: %w", err)
 	}
 
-	fmt.Fprintf(p.out, "%s\n", buf.String())
+	if !p.omitEmpty || buf.Len() > 0 {
+		fmt.Fprintf(p.out, "%s\n", buf.String())
+	}
 
 	return nil
 }

pkg/genericcli/printers/template_test.go

@@ -91,5 +91,41 @@ func TestTemplatePrinter_WithTemplate(t *testing.T) {
 	if diff := cmp.Diff(want, got); diff != "" {
 		t.Errorf("diff (+got -want):\n %s", diff)
 	}
+}
+
+func TestTemplatePrinter_OmitEmptyRowsInSliceResponses(t *testing.T) {
+	type obj struct {
+		Name string `json:"name"`
+	}
+
+	var (
+		out      bytes.Buffer
+		out2     bytes.Buffer
+		tpl      = `{{ if eq .name "test" }}{{ .name }}{{ end }}`
+		testObjs = []obj{{Name: "a"}, {Name: "test"}}
+	)
+
+	p := NewTemplatePrinter(tpl).WithOut(&out)
+	err := p.Print(testObjs)
+	if err != nil {
+		t.Error(err)
+	}
+
+	want := "test\n"
+	got := out.String()
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("diff (+got -want):\n %s", diff)
+	}
+
+	p = NewTemplatePrinter(tpl).WithOut(&out2).WithoutOmitEmptyLines()
+	err = p.Print(testObjs)
+	if err != nil {
+		t.Error(err)
+	}
 
+	want = "\ntest\n"
+	got = out2.String()
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("diff (+got -want):\n %s", diff)
+	}
 }