From 331add614779f52653ce1c598e1c8be81834cd3c Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Wed, 27 Nov 2024 16:47:08 +0900
Subject: [PATCH] Implement SetOmitEmpty() (#89)

---
 pp.go      |  9 ++++++++
 pp_test.go | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 printer.go | 16 ++++++++++----
 3 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/pp.go b/pp.go
index bac9958..ec4c9d4 100644
--- a/pp.go
+++ b/pp.go
@@ -49,6 +49,9 @@ type PrettyPrinter struct {
 	thousandsSeparator bool
 	// This skips unexported fields of structs.
 	exportedOnly bool
+
+	// This skips empty fields of structs.
+	omitEmpty bool
 }
 
 // New creates a new PrettyPrinter that can be used to pretty print values
@@ -66,6 +69,7 @@ func newPrettyPrinter(callerLevel int) *PrettyPrinter {
 		coloringEnabled: true,
 		decimalUint:     true,
 		exportedOnly:    false,
+		omitEmpty:       false,
 	}
 }
 
@@ -149,6 +153,11 @@ func (pp *PrettyPrinter) SetExportedOnly(enabled bool) {
 	pp.exportedOnly = enabled
 }
 
+// SetOmitEmpty makes empty fields in struct not be printed.
+func (pp *PrettyPrinter) SetOmitEmpty(enabled bool) {
+	pp.omitEmpty = enabled
+}
+
 func (pp *PrettyPrinter) SetThousandsSeparator(enabled bool) {
 	pp.thousandsSeparator = enabled
 }
diff --git a/pp_test.go b/pp_test.go
index aa9e962..6104025 100644
--- a/pp_test.go
+++ b/pp_test.go
@@ -160,3 +160,66 @@ func TestStructPrintingWithTags(t *testing.T) {
 	}
 
 }
+
+func TestStructPrintingWithOmitEmpty(t *testing.T) {
+	type Bar struct{ StringField string }
+	type Foo struct {
+		StringField string
+		StringPtr   *string
+
+		StructField    Bar
+		StructPtr      *Bar
+		InterfactField interface{}
+	}
+
+	stringVal := "foo"
+
+	testCases := []struct {
+		name               string
+		foo                Foo
+		omitIfEmptyOmitted bool
+		fullOmitted        bool
+		want               string
+	}{
+		{
+			name: "all set",
+			foo: Foo{
+				StringField: "foo",
+				StringPtr:   &stringVal,
+				StructField: Bar{
+					StringField: "baz",
+				},
+				StructPtr: &Bar{
+					StringField: "foobar",
+				},
+				InterfactField: &Bar{StringField: "fizzbuzz"},
+			},
+			want: "pp.Foo{\n  StringField: \"foo\",\n  StringPtr:   &\"foo\",\n  StructField: pp.Bar{\n    StringField: \"baz\",\n  },\n  StructPtr: &pp.Bar{\n    StringField: \"foobar\",\n  },\n  InterfactField: &pp.Bar{\n    StringField: \"fizzbuzz\",\n  },\n}",
+		},
+		{
+			name: "zero",
+			foo:  Foo{},
+			want: "pp.Foo{}",
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			output := new(bytes.Buffer)
+			pp := New()
+			pp.SetOutput(output)
+			pp.SetColoringEnabled(false)
+			pp.SetOmitEmpty(true)
+
+			pp.Print(tc.foo)
+
+			result := output.String()
+
+			if result != tc.want {
+				t.Errorf("result differ, want: %q, got: %q", tc.want, result)
+			}
+		})
+	}
+
+}
diff --git a/printer.go b/printer.go
index 13e0a0a..ef3c889 100644
--- a/printer.go
+++ b/printer.go
@@ -22,10 +22,10 @@ const (
 )
 
 func (pp *PrettyPrinter) format(object interface{}) string {
-	return newPrinter(object, &pp.currentScheme, pp.maxDepth, pp.coloringEnabled, pp.decimalUint, pp.exportedOnly, pp.thousandsSeparator).String()
+	return newPrinter(object, &pp.currentScheme, pp.maxDepth, pp.coloringEnabled, pp.decimalUint, pp.exportedOnly, pp.thousandsSeparator, pp.omitEmpty).String()
 }
 
-func newPrinter(object interface{}, currentScheme *ColorScheme, maxDepth int, coloringEnabled bool, decimalUint bool, exportedOnly bool, thousandsSeparator bool) *printer {
+func newPrinter(object interface{}, currentScheme *ColorScheme, maxDepth int, coloringEnabled bool, decimalUint bool, exportedOnly bool, thousandsSeparator bool, omitEmpty bool) *printer {
 	buffer := bytes.NewBufferString("")
 	tw := new(tabwriter.Writer)
 	tw.Init(buffer, indentWidth, 0, 1, ' ', 0)
@@ -42,6 +42,7 @@ func newPrinter(object interface{}, currentScheme *ColorScheme, maxDepth int, co
 		decimalUint:        decimalUint,
 		exportedOnly:       exportedOnly,
 		thousandsSeparator: thousandsSeparator,
+		omitEmpty:          omitEmpty,
 	}
 
 	if thousandsSeparator {
@@ -63,6 +64,7 @@ type printer struct {
 	decimalUint        bool
 	exportedOnly       bool
 	thousandsSeparator bool
+	omitEmpty          bool
 	localizedPrinter   *message.Printer
 }
 
@@ -212,7 +214,13 @@ func (p *printer) printStruct() {
 		if p.exportedOnly && field.PkgPath != "" {
 			continue
 		}
-		// ignore fields if zero value, or explicitly set
+
+		// ignore empty fields if needed
+		if p.omitEmpty && valueIsZero(value) {
+			continue
+		}
+
+		// ignore fields with struct tags if zero value, or explicitly set
 		if tag := field.Tag.Get("pp"); tag != "" {
 			parts := strings.Split(tag, ",")
 			if len(parts) == 2 && parts[1] == "omitempty" && valueIsZero(value) {
@@ -469,7 +477,7 @@ func (p *printer) colorize(text string, color uint16) string {
 }
 
 func (p *printer) format(object interface{}) string {
-	pp := newPrinter(object, p.currentScheme, p.maxDepth, p.coloringEnabled, p.decimalUint, p.exportedOnly, p.thousandsSeparator)
+	pp := newPrinter(object, p.currentScheme, p.maxDepth, p.coloringEnabled, p.decimalUint, p.exportedOnly, p.thousandsSeparator, false)
 	pp.depth = p.depth
 	pp.visited = p.visited
 	if value, ok := object.(reflect.Value); ok {