Do not emit surrounding whitespace for text nodes

Previously we omitted extra whitespace for single PCDATA/CDATA children, but in
mixed content there was extra indentation before/after text nodes.

One of the problems with that is that the text that you saved is not exactly
the same as the parsing result using default flags (parse_trim_pcdata helps).

Another problem is that parse-format cycles do not have a fixed point for mixed
content - the result expands indefinitely. Some XML libraries, like Python
minidom, have the same issue, but this is definitely a problem.

Pretty-printing mixed content is hard. It seems that the only other sensible
choice is to switch mixed content nodes to raw formatting. In a way the code in
this change is a weaker version of that - it removes indentation around text
nodes but still keeps it around element siblings/children.

Thus we can switch to mixed-raw formatting at some point later, which will be
a superset of the current behavior.

To do this we have to either switch at the first text node (.NET XmlDocument
does that), or scan the children of each element for a possible text node and
switch before we output the first child.

The former behavior seems non-intuitive (and a bit broken); unfortunately, the
latter behavior can cost up to 20% of the output time for trees *without* mixed
content.

Fixes #13.

3 files changed, 111 insertions, 72 deletions

diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index 4269335..ac90c5f 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -3511,61 +3511,28 @@ PUGI__NS_BEGIN
 		if (node->first_attribute)
 			node_output_attributes(writer, node, flags);
 
-		if (flags & format_raw)
+		if (!node->first_child)
 		{
-			if (!node->first_child)
-				writer.write(' ', '/', '>');
-			else
-			{
-				writer.write('>');
+			writer.write(' ', '/', '>');
 
-				return true;
-			}
+			return false;
 		}
 		else
 		{
-			xml_node_struct* first = node->first_child;
-
-			if (!first)
-				writer.write(' ', '/', '>', '\n');
-			else if (!first->next_sibling && (PUGI__NODETYPE(first) == node_pcdata || PUGI__NODETYPE(first) == node_cdata))
-			{
-				writer.write('>');
-
-				const char_t* value = first->value ? first->value : PUGIXML_TEXT("");
-
-				if (PUGI__NODETYPE(first) == node_pcdata)
-					text_output(writer, value, ctx_special_pcdata, flags);
-				else
-					text_output_cdata(writer, value);
-
-				writer.write('<', '/');
-				writer.write_string(name);
-				writer.write('>', '\n');
-			}
-			else
-			{
-				writer.write('>', '\n');
+			writer.write('>');
 
-				return true;
-			}
+			return true;
 		}
-
-		return false;
 	}
 
-	PUGI__FN void node_output_end(xml_buffered_writer& writer, xml_node_struct* node, unsigned int flags)
+	PUGI__FN void node_output_end(xml_buffered_writer& writer, xml_node_struct* node)
 	{
 		const char_t* default_name = PUGIXML_TEXT(":anonymous");
 		const char_t* name = node->name ? node->name : default_name;
 
 		writer.write('<', '/');
 		writer.write_string(name);
-
-		if (flags & format_raw)
-			writer.write('>');
-		else
-			writer.write('>', '\n');
+		writer.write('>');
 	}
 
 	PUGI__FN void node_output_simple(xml_buffered_writer& writer, xml_node_struct* node, unsigned int flags)
@@ -3576,17 +3543,14 @@ PUGI__NS_BEGIN
 		{
 			case node_pcdata:
 				text_output(writer, node->value ? node->value : PUGIXML_TEXT(""), ctx_special_pcdata, flags);
-				if ((flags & format_raw) == 0) writer.write('\n');
 				break;
 
 			case node_cdata:
 				text_output_cdata(writer, node->value ? node->value : PUGIXML_TEXT(""));
-				if ((flags & format_raw) == 0) writer.write('\n');
 				break;
 
 			case node_comment:
 				node_output_comment(writer, node->value ? node->value : PUGIXML_TEXT(""));
-				if ((flags & format_raw) == 0) writer.write('\n');
 				break;
 
 			case node_pi:
@@ -3600,7 +3564,6 @@ PUGI__NS_BEGIN
 				}
 
 				writer.write('?', '>');
-				if ((flags & format_raw) == 0) writer.write('\n');
 				break;
 
 			case node_declaration:
@@ -3608,7 +3571,6 @@ PUGI__NS_BEGIN
 				writer.write_string(node->name ? node->name : default_name);
 				node_output_attributes(writer, node, flags);
 				writer.write('?', '>');
-				if ((flags & format_raw) == 0) writer.write('\n');
 				break;
 
 			case node_doctype:
@@ -3622,7 +3584,6 @@ PUGI__NS_BEGIN
 				}
 
 				writer.write('>');
-				if ((flags & format_raw) == 0) writer.write('\n');
 				break;
 
 			default:
@@ -3630,9 +3591,16 @@ PUGI__NS_BEGIN
 		}
 	}
 
+	enum indent_flags_t
+	{
+		indent_newline = 1,
+		indent_indent = 2
+	};
+
 	PUGI__FN void node_output(xml_buffered_writer& writer, xml_node_struct* root, const char_t* indent, unsigned int flags, unsigned int depth)
 	{
 		size_t indent_length = ((flags & (format_indent | format_raw)) == format_indent) ? strlength(indent) : 0;
+		unsigned int indent_flags = indent_indent;
 
 		xml_node_struct* node = root;
 
@@ -3641,29 +3609,47 @@ PUGI__NS_BEGIN
 			assert(node);
 
 			// begin writing current node
-			if (indent_length)
-				text_output_indent(writer, indent, indent_length, depth);
+			if (PUGI__NODETYPE(node) == node_pcdata || PUGI__NODETYPE(node) == node_cdata)
+			{
+				node_output_simple(writer, node, flags);
 
-			if (PUGI__NODETYPE(node) == node_element)
+				indent_flags = 0;
+			}
+			else
 			{
-				if (node_output_start(writer, node, flags))
+				if ((indent_flags & indent_newline) && (flags & format_raw) == 0)
+					writer.write('\n');
+
+				if ((indent_flags & indent_indent) && indent_length)
+					text_output_indent(writer, indent, indent_length, depth);
+
+				if (PUGI__NODETYPE(node) == node_element)
 				{
-					node = node->first_child;
-					depth++;
-					continue;
+					indent_flags = indent_newline | indent_indent;
+
+					if (node_output_start(writer, node, flags))
+					{
+						node = node->first_child;
+						depth++;
+						continue;
+					}
 				}
-			}
-			else if (PUGI__NODETYPE(node) == node_document)
-			{
-				if (node->first_child)
+				else if (PUGI__NODETYPE(node) == node_document)
 				{
-					node = node->first_child;
-					continue;
+					indent_flags = indent_indent;
+
+					if (node->first_child)
+					{
+						node = node->first_child;
+						continue;
+					}
+				}
+				else
+				{
+					node_output_simple(writer, node, flags);
+
+					indent_flags = indent_newline | indent_indent;
 				}
-			}
-			else
-			{
-				node_output_simple(writer, node, flags);
 			}
 
 			// continue to the next node
@@ -3682,14 +3668,22 @@ PUGI__NS_BEGIN
 				{
 					depth--;
 
-					if (indent_length)
+					if ((indent_flags & indent_newline) && (flags & format_raw) == 0)
+						writer.write('\n');
+
+					if ((indent_flags & indent_indent) && indent_length)
 						text_output_indent(writer, indent, indent_length, depth);
 
-					node_output_end(writer, node, flags);
+					node_output_end(writer, node);
+
+					indent_flags = indent_newline | indent_indent;
 				}
 			}
 		}
 		while (node != root);
+
+		if ((indent_flags & indent_newline) && (flags & format_raw) == 0)
+			writer.write('\n');
 	}
 
 	PUGI__FN bool has_declaration(xml_node_struct* node)
diff --git a/tests/test_write.cpp b/tests/test_write.cpp
index 59cdb3e..a61e1cf 100644
--- a/tests/test_write.cpp
+++ b/tests/test_write.cpp
@@ -22,19 +22,19 @@ TEST_XML(write_indent, "<node attr='1'><child><sub>text</sub></child></node>")
 
 TEST_XML(write_pcdata, "<node attr='1'><child><sub/>text</child></node>")
 {
-	CHECK_NODE_EX(doc, STR("<node attr=\"1\">\n\t<child>\n\t\t<sub />\n\t\ttext\n\t</child>\n</node>\n"), STR("\t"), format_indent);
+	CHECK_NODE_EX(doc, STR("<node attr=\"1\">\n\t<child>\n\t\t<sub />text</child>\n</node>\n"), STR("\t"), format_indent);
 }
 
 TEST_XML_FLAGS(write_cdata, "<![CDATA[value]]>", parse_cdata | parse_fragment)
 {
 	CHECK_NODE(doc, STR("<![CDATA[value]]>"));
-	CHECK_NODE_EX(doc, STR("<![CDATA[value]]>\n"), STR(""), 0);
+	CHECK_NODE_EX(doc, STR("<![CDATA[value]]>"), STR(""), 0);
 }
 
 TEST_XML_FLAGS(write_cdata_empty, "<![CDATA[]]>", parse_cdata | parse_fragment)
 {
 	CHECK_NODE(doc, STR("<![CDATA[]]>"));
-	CHECK_NODE_EX(doc, STR("<![CDATA[]]>\n"), STR(""), 0);
+	CHECK_NODE_EX(doc, STR("<![CDATA[]]>"), STR(""), 0);
 }
 
 TEST_XML_FLAGS(write_cdata_escape, "<![CDATA[value]]>", parse_cdata | parse_fragment)
@@ -527,5 +527,50 @@ TEST(write_pcdata_null)
 
 	doc.first_child().append_child(node_pcdata);
 
-	CHECK_NODE_EX(doc, STR("<node>\n\t\n\t\n</node>\n"), STR("\t"), format_indent);
+	CHECK_NODE_EX(doc, STR("<node></node>\n"), STR("\t"), format_indent);
+}
+
+TEST(write_pcdata_whitespace_fixedpoint)
+{
+	const char_t* data = STR("<node>  test  <child>\n  <sub/>\n   </child>\n</node>");
+
+	static const unsigned int flags_parse[] =
+	{
+		0,
+		parse_ws_pcdata,
+		parse_ws_pcdata_single,
+		parse_trim_pcdata
+	};
+
+	static const unsigned int flags_format[] =
+	{
+		0,
+		format_raw,
+		format_indent
+	};
+
+	for (unsigned int i = 0; i < sizeof(flags_parse) / sizeof(flags_parse[0]); ++i)
+	{
+		xml_document doc;
+		CHECK(doc.load_string(data, flags_parse[i]));
+
+		for (unsigned int j = 0; j < sizeof(flags_format) / sizeof(flags_format[0]); ++j)
+		{
+			std::string saved = write_narrow(doc, flags_format[j], encoding_auto);
+
+			xml_document rdoc;
+			CHECK(rdoc.load_buffer(&saved[0], saved.size(), flags_parse[i]));
+
+			std::string rsaved = write_narrow(rdoc, flags_format[j], encoding_auto);
+
+			CHECK(saved == rsaved);
+		}
+	}
+}
+
+TEST_XML_FLAGS(write_mixed, "<node><child1/><child2>pre<![CDATA[data]]>mid<!--comment--><test/>post<?pi value?>fin</child2><child3/></node>", parse_full)
+{
+	CHECK_NODE(doc, "<node><child1 /><child2>pre<![CDATA[data]]>mid<!--comment--><test />post<?pi value?>fin</child2><child3 /></node>");
+	CHECK_NODE_EX(doc, "<node>\n<child1 />\n<child2>pre<![CDATA[data]]>mid<!--comment-->\n<test />post<?pi value?>fin</child2>\n<child3 />\n</node>\n", STR("\t"), 0);
+	CHECK_NODE_EX(doc, "<node>\n\t<child1 />\n\t<child2>pre<![CDATA[data]]>mid<!--comment-->\n\t\t<test />post<?pi value?>fin</child2>\n\t<child3 />\n</node>\n", STR("\t"), format_indent);
 }
diff --git a/tests/writer_string.cpp b/tests/writer_string.cpp
index 661c792..26bca8d 100644
--- a/tests/writer_string.cpp
+++ b/tests/writer_string.cpp
@@ -45,7 +45,7 @@ std::string save_narrow(const pugi::xml_document& doc, unsigned int flags, pugi:
 {
 	xml_writer_string writer;
 
-	doc.save(writer, STR(""), flags, encoding);
+	doc.save(writer, STR("\t"), flags, encoding);
 
 	return writer.as_narrow();
 }
@@ -59,7 +59,7 @@ std::string write_narrow(pugi::xml_node node, unsigned int flags, pugi::xml_enco
 {
 	xml_writer_string writer;
 
-	node.print(writer, STR(""), flags, encoding);
+	node.print(writer, STR("\t"), flags, encoding);
 
 	return writer.as_narrow();
 }
@@ -73,7 +73,7 @@ std::basic_string<wchar_t> write_wide(pugi::xml_node node, unsigned int flags, p
 {
 	xml_writer_string writer;
 
-	node.print(writer, STR(""), flags, encoding);
+	node.print(writer, STR("\t"), flags, encoding);
 
 	return writer.as_wide();
 }