Fix YAML output issue with empty structures

Add checks to spot empty structures such as empty map or empty list
to properly display its empty inline JSON style in the YAML output.

assets/examples/styles-and-types.yml

@@ -16,6 +16,10 @@ yaml:
           lines to offer
 
         inlinejson: { key: [A, B, C] }
+        emptyMap: {}
+        emptyList: []
+        emptyWhatever-1: ~
+        emptyWhatever-2: NULL
 
       list:
       - one

pkg/neat/neat.go

@@ -31,13 +31,15 @@ import (
 )
 
 var (
-	keyColor           = bunt.Coral
+	keyColor           = bunt.IndianRed
 	indentLineColor    = bunt.Color(0x00242424)
 	scalarDefaultColor = bunt.PaleGreen
 	boolColor          = bunt.Moccasin
 	floatColor         = bunt.Orange
 	intColor           = bunt.MediumPurple
 	multiLineTextColor = bunt.Aquamarine
+	nullColor          = bunt.DarkOrange
+	emptyStructures    = bunt.PaleGoldenrod
 )
 
 // ToYAMLString marshals the provided object into YAML with text decorations
@@ -49,9 +51,7 @@ func ToYAMLString(obj interface{}) (string, error) {
 		return "", err
 	}
 
-	writer.WriteString("\n")
 	writer.Flush()
-
 	return buf.String(), nil
 }
 
@@ -91,15 +91,28 @@ func neatMapSlice(out *bufio.Writer, prefix string, skipIndentOnFirstLine bool,
 
 		switch mapitem.Value.(type) {
 		case yaml.MapSlice:
-			out.WriteString("\n")
-			if err := neatMapSlice(out, prefix+prefixAdd(), false, mapitem.Value.(yaml.MapSlice)); err != nil {
-				return err
+			if len(mapitem.Value.(yaml.MapSlice)) == 0 {
+				out.WriteString(" ")
+				out.WriteString(bunt.Colorize("{}", emptyStructures))
+				out.WriteString("\n")
+
+			} else {
+				out.WriteString("\n")
+				if err := neatMapSlice(out, prefix+prefixAdd(), false, mapitem.Value.(yaml.MapSlice)); err != nil {
+					return err
+				}
 			}
 
 		case []interface{}:
-			out.WriteString("\n")
-			if err := neatSlice(out, prefix, false, mapitem.Value.([]interface{})); err != nil {
-				return err
+			if len(mapitem.Value.([]interface{})) == 0 {
+				out.WriteString(" ")
+				out.WriteString(bunt.Colorize("[]", emptyStructures))
+				out.WriteString("\n")
+			} else {
+				out.WriteString("\n")
+				if err := neatSlice(out, prefix, false, mapitem.Value.([]interface{})); err != nil {
+					return err
+				}
 			}
 
 		default:
@@ -138,6 +151,14 @@ func neatMapSliceSlice(out *bufio.Writer, prefix string, skipIndentOnFirstLine b
 }
 
 func neatScalar(out *bufio.Writer, prefix string, skipIndentOnFirstLine bool, obj interface{}) error {
+	// Process nil values immediately and return afterwards
+	if obj == nil {
+		out.WriteString(bunt.Colorize("null", nullColor))
+		out.WriteString("\n")
+		return nil
+	}
+
+	// Any other value: Run through Go YAML marshaller and colorize afterwards
 	data, err := yaml.Marshal(obj)
 	if err != nil {
 		return err