refactor: focus around Render/Compact/Pretty/NewWith functions

This is yet another drastic refactor of public API and concepts.
Hopefully the last one, as I'm now fairly happy with things.

xml.go

@@ -6,36 +6,49 @@ import (
 	"io"
 )
 
+// XMLDefualtIndent is the default indentation string used by XML instances when
+// pretty rendering if no Indent value is set.
+var XMLDefualtIndent = "  "
+
 // XML is a Renderer that marshals a value to XML.
 type XML struct {
-	// Pretty specifies whether the output should be pretty-printed. If true,
-	// the output will be indented and newlines will be added.
-	Pretty bool
-
-	// Prefix is the prefix added to each level of indentation when Pretty is
-	// true.
+	// Prefix is the prefix added to each level of indentation when pretty
+	// rendering.
 	Prefix string
 
-	// Indent is the string added to each level of indentation when Pretty is
-	// true. If empty, two spaces will be used instead.
+	// Indent is the string added to each level of indentation when pretty
+	// rendering. If empty, XMLDefualtIndent be used.
 	Indent string
 }
 
-var _ FormatRenderer = (*XML)(nil)
+var (
+	_ Handler        = (*XML)(nil)
+	_ PrettyHandler  = (*XML)(nil)
+	_ FormatsHandler = (*XML)(nil)
+)
 
 // Render marshals the given value to XML.
 func (x *XML) Render(w io.Writer, v any) error {
-	enc := xml.NewEncoder(w)
-	if x.Pretty {
-		prefix := x.Prefix
-		indent := x.Indent
-		if indent == "" {
-			indent = "  "
-		}
-
-		enc.Indent(prefix, indent)
+	err := xml.NewEncoder(w).Encode(v)
+	if err != nil {
+		return fmt.Errorf("%w: %w", ErrFailed, err)
 	}
 
+	return nil
+}
+
+// RenderPretty marshals the given value to XML with line breaks and
+// indentation.
+func (x *XML) RenderPretty(w io.Writer, v any) error {
+	prefix := x.Prefix
+	indent := x.Indent
+	if indent == "" {
+		indent = XMLDefualtIndent
+	}
+
+	enc := xml.NewEncoder(w)
+	enc.Indent(prefix, indent)
+
 	err := enc.Encode(v)
 	if err != nil {
 		return fmt.Errorf("%w: %w", ErrFailed, err)
@@ -44,6 +57,7 @@ func (x *XML) Render(w io.Writer, v any) error {
 	return nil
 }
 
+// Formats returns a list of format strings that this Handler supports.
 func (x *XML) Formats() []string {
 	return []string{"xml"}
 }