From 9fa2f0a5109de4de6749d7a310910c6da9cdc23d Mon Sep 17 00:00:00 2001
From: Sergey Ratkevich <ratkevich@syntellect.ru>
Date: Mon, 13 Jan 2025 14:23:05 +0300
Subject: [PATCH] Immediate returning errors in xml output.

Especially valuable for Write and WriteWithOptions
---
 node.go | 123 ++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 83 insertions(+), 40 deletions(-)

diff --git a/node.go b/node.go
index 03e0ce9..43b2a8e 100644
--- a/node.go
+++ b/node.go
@@ -155,7 +155,7 @@ type indentation struct {
 	level    int
 	hasChild bool
 	indent   string
-	w io.Writer
+	w        io.Writer
 }
 
 func newIndentation(indent string, w io.Writer) *indentation {
@@ -168,101 +168,139 @@ func newIndentation(indent string, w io.Writer) *indentation {
 	}
 }
 
-func (i *indentation) NewLine() {
+func (i *indentation) NewLine() (err error) {
 	if i == nil {
 		return
 	}
-	io.WriteString(i.w, "\n")
+	_, err = io.WriteString(i.w, "\n")
+	return
 }
 
-func (i *indentation) Open() {
+func (i *indentation) Open() (err error) {
 	if i == nil {
 		return
 	}
 
-	io.WriteString(i.w, "\n")
-	io.WriteString(i.w, strings.Repeat(i.indent, i.level))
+	if err = i.writeIndent(); err != nil {
+		return
+	}
 
 	i.level++
 	i.hasChild = false
+	return
 }
 
-func (i *indentation) Close() {
+func (i *indentation) Close() (err error) {
 	if i == nil {
 		return
 	}
 	i.level--
 	if i.hasChild {
-		io.WriteString(i.w, "\n")
-		io.WriteString(i.w, strings.Repeat(i.indent, i.level))
+		if err = i.writeIndent(); err != nil {
+			return
+		}
 	}
 	i.hasChild = true
+	return
+}
+
+func (i *indentation) writeIndent() (err error) {
+	_, err = io.WriteString(i.w, "\n")
+	if err != nil {
+		return
+	}
+	_, err = io.WriteString(i.w, strings.Repeat(i.indent, i.level))
+	return
 }
 
-func outputXML(w io.Writer, n *Node, preserveSpaces bool, config *outputConfiguration, indent *indentation) {
+func outputXML(w io.Writer, n *Node, preserveSpaces bool, config *outputConfiguration, indent *indentation) (err error) {
 	preserveSpaces = calculatePreserveSpaces(n, preserveSpaces)
 	switch n.Type {
 	case TextNode:
-		io.WriteString(w, html.EscapeString(n.sanitizedData(preserveSpaces)))
+		_, err = io.WriteString(w, html.EscapeString(n.sanitizedData(preserveSpaces)))
 		return
 	case CharDataNode:
-		io.WriteString(w, "<![CDATA[")
-		io.WriteString(w, n.Data)
-		io.WriteString(w, "]]>")
+		_, err = fmt.Fprintf(w, "<![CDATA[%v]]>", n.Data)
 		return
 	case CommentNode:
 		if !config.skipComments {
-			io.WriteString(w, "<!--")
-			io.WriteString(w, n.Data)
-			io.WriteString(w, "-->")
+			_, err = fmt.Fprintf(w, "<!--%v-->", n.Data)
 		}
 		return
 	case NotationNode:
-		indent.NewLine()
-		fmt.Fprintf(w, "<!%s>", n.Data)
+		if err = indent.NewLine(); err != nil {
+			return
+		}
+		_, err = fmt.Fprintf(w, "<!%s>", n.Data)
 		return
 	case DeclarationNode:
-		io.WriteString(w, "<?" + n.Data)
+		_, err = io.WriteString(w, "<?"+n.Data)
+		if err != nil {
+			return
+		}
 	default:
-		indent.Open()
+		if err = indent.Open(); err != nil {
+			return
+		}
 		if n.Prefix == "" {
-			io.WriteString(w, "<" + n.Data)
+			_, err = io.WriteString(w, "<"+n.Data)
 		} else {
-			fmt.Fprintf(w, "<%s:%s", n.Prefix, n.Data)
+			_, err = fmt.Fprintf(w, "<%s:%s", n.Prefix, n.Data)
+		}
+		if err != nil {
+			return
 		}
 	}
 
 	for _, attr := range n.Attr {
 		if attr.Name.Space != "" {
-			fmt.Fprintf(w, ` %s:%s=`, attr.Name.Space, attr.Name.Local)
+			_, err = fmt.Fprintf(w, ` %s:%s=`, attr.Name.Space, attr.Name.Local)
 		} else {
-			fmt.Fprintf(w, ` %s=`, attr.Name.Local)
+			_, err = fmt.Fprintf(w, ` %s=`, attr.Name.Local)
+		}
+		if err != nil {
+			return
 		}
 
-		fmt.Fprintf(w, `"%v"`, html.EscapeString(attr.Value))
+		_, err = fmt.Fprintf(w, `"%v"`, html.EscapeString(attr.Value))
+		if err != nil {
+			return
+		}
 	}
 	if n.Type == DeclarationNode {
-		io.WriteString(w, "?>")
+		_, err = io.WriteString(w, "?>")
 	} else {
 		if n.FirstChild != nil || !config.emptyElementTagSupport {
-			io.WriteString(w, ">")
+			_, err = io.WriteString(w, ">")
 		} else {
-			io.WriteString(w, "/>")
-			indent.Close()
+			_, err = io.WriteString(w, "/>")
+			if err != nil {
+				return
+			}
+			err = indent.Close()
 			return
 		}
 	}
+	if err != nil {
+		return
+	}
 	for child := n.FirstChild; child != nil; child = child.NextSibling {
-		outputXML(w, child, preserveSpaces, config, indent)
+		err = outputXML(w, child, preserveSpaces, config, indent)
+		if err != nil {
+			return
+		}
 	}
 	if n.Type != DeclarationNode {
-		indent.Close()
+		if err = indent.Close(); err != nil {
+			return
+		}
 		if n.Prefix == "" {
-			fmt.Fprintf(w, "</%s>", n.Data)
+			_, err = fmt.Fprintf(w, "</%s>", n.Data)
 		} else {
-			fmt.Fprintf(w, "</%s:%s>", n.Prefix, n.Data)
+			_, err = fmt.Fprintf(w, "</%s:%s>", n.Prefix, n.Data)
 		}
 	}
+	return
 }
 
 // OutputXML returns the text that including tags name.
@@ -281,15 +319,15 @@ func (n *Node) OutputXMLWithOptions(opts ...OutputOption) string {
 }
 
 // Write writes xml to given writer.
-func (n *Node) Write(writer io.Writer, self bool) {
+func (n *Node) Write(writer io.Writer, self bool) error {
 	if self {
-		n.WriteWithOptions(writer, WithOutputSelf())
+		return n.WriteWithOptions(writer, WithOutputSelf())
 	}
-	n.WriteWithOptions(writer)
+	return n.WriteWithOptions(writer)
 }
 
 // WriteWithOptions writes xml with given options to given writer.
-func (n *Node) WriteWithOptions(writer io.Writer, opts ...OutputOption) {
+func (n *Node) WriteWithOptions(writer io.Writer, opts ...OutputOption) (err error) {
 	config := &outputConfiguration{}
 	// Set the options
 	for _, opt := range opts {
@@ -300,13 +338,18 @@ func (n *Node) WriteWithOptions(writer io.Writer, opts ...OutputOption) {
 	b := bufio.NewWriter(writer)
 	defer b.Flush()
 
+	ident := newIndentation(config.useIndentation, b)
 	if config.printSelf && n.Type != DocumentNode {
-		outputXML(b, n, preserveSpaces, config, newIndentation(config.useIndentation, b))
+		err = outputXML(b, n, preserveSpaces, config, ident)
 	} else {
 		for n := n.FirstChild; n != nil; n = n.NextSibling {
-			outputXML(b, n, preserveSpaces, config, newIndentation(config.useIndentation, b))
+			err = outputXML(b, n, preserveSpaces, config, ident)
+			if err != nil {
+				break
+			}
 		}
 	}
+	return
 }
 
 // AddAttr adds a new attribute specified by 'key' and 'val' to a node 'n'.