fix(fmt): Preserve multiple newlines between elements (#374)

parser/v2/elementparser.go

@@ -471,7 +471,7 @@ func addTrailingSpaceAndValidate(start parse.Position, e Element, pi *parse.Inpu
 	if err != nil {
 		return e, false, err
 	}
-	e.TrailingSpace, err = NewTrailingSpace(ws)
+	e.TrailingSpace, err = NewTrailingSpace(ws, true)
 	if err != nil {
 		return e, false, err
 	}

parser/v2/elementparser_test.go

@@ -1538,6 +1538,43 @@ func TestElementParser(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "element: with multiple newlines, should collapse to two",
+			input: `<div>
+	<span></span>
+
+
+
+	<span></span>
+</div>`,
+			expected: Element{
+				Name: "div",
+				NameRange: Range{
+					From: Position{Index: 1, Line: 0, Col: 1},
+					To:   Position{Index: 4, Line: 0, Col: 4},
+				},
+				IndentChildren: true,
+				Children: []Node{
+					Whitespace{Value: "\n\t"},
+					Element{
+						Name: "span",
+						NameRange: Range{
+							From: Position{Index: 8, Line: 1, Col: 2},
+							To:   Position{Index: 12, Line: 1, Col: 6},
+						},
+						TrailingSpace: SpaceVerticalDouble,
+					},
+					Element{
+						Name: "span",
+						NameRange: Range{
+							From: Position{Index: 26, Line: 5, Col: 2},
+							To:   Position{Index: 30, Line: 5, Col: 6},
+						},
+						TrailingSpace: SpaceVertical,
+					},
+				},
+			},
+		},
 		{
 			name: "element: can contain text that starts with for",
 			input: `<div>for which any 

parser/v2/formattestdata/element_double_newline_is_preserved.txt

@@ -0,0 +1,28 @@
+-- in --
+package main
+
+templ x() {
+  <div>
+    <span>Hello
+
+    World
+    </span>
+
+
+
+    <span>Foo Bar </span>
+  </div>
+}
+-- out --
+package main
+
+templ x() {
+	<div>
+		<span>
+			Hello
+			World
+		</span>
+
+		<span>Foo Bar </span>
+	</div>
+}

parser/v2/gocodeparser.go

@@ -36,7 +36,7 @@ var goCode = parse.Func(func(pi *parse.Input) (n Node, ok bool, err error) {
 	if err != nil {
 		return r, false, err
 	}
-	r.TrailingSpace, err = NewTrailingSpace(ws)
+	r.TrailingSpace, err = NewTrailingSpace(ws, true)
 	if err != nil {
 		return r, false, err
 	}

parser/v2/stringexpressionparser.go

@@ -30,7 +30,7 @@ var stringExpression = parse.Func(func(pi *parse.Input) (n Node, ok bool, err er
 	if err != nil {
 		return r, false, err
 	}
-	r.TrailingSpace, err = NewTrailingSpace(ws)
+	r.TrailingSpace, err = NewTrailingSpace(ws, false)
 	if err != nil {
 		return r, false, err
 	}

parser/v2/textparser.go

@@ -35,7 +35,7 @@ var textParser = parse.Func(func(pi *parse.Input) (n Node, ok bool, err error) {
 	if err != nil {
 		return t, false, err
 	}
-	t.TrailingSpace, err = NewTrailingSpace(ws)
+	t.TrailingSpace, err = NewTrailingSpace(ws, false)
 	if err != nil {
 		return t, false, err
 	}

parser/v2/textparser_test.go

@@ -80,7 +80,7 @@ func TestTextParser(t *testing.T) {
 			},
 		},
 		{
-			name:  "Multiline text is colected line by line",
+			name:  "Multiline text is collected line by line",
 			input: "Line 1\nLine 2",
 			expected: Text{
 				Value: "Line 1",
@@ -92,7 +92,7 @@ func TestTextParser(t *testing.T) {
 			},
 		},
 		{
-			name:  "Multiline text is colected line by line (Windows)",
+			name:  "Multiline text is collected line by line (Windows)",
 			input: "Line 1\r\nLine 2",
 			expected: Text{
 				Value: "Line 1",
@@ -103,6 +103,18 @@ func TestTextParser(t *testing.T) {
 				TrailingSpace: "\n",
 			},
 		},
+		{
+			name:  "Multiline text with multiple newlines is collected line by line",
+			input: "Line 1\n\n\n\nLine 2",
+			expected: Text{
+				Value: "Line 1",
+				Range: Range{
+					From: Position{Index: 0, Line: 0, Col: 0},
+					To:   Position{Index: 6, Line: 0, Col: 6},
+				},
+				TrailingSpace: "\n",
+			},
+		},
 	}
 	for _, tt := range tests {
 		tt := tt

parser/v2/types.go

@@ -375,17 +375,27 @@ func (t HTMLTemplate) Write(w io.Writer, indent int) error {
 type TrailingSpace string
 
 const (
-	SpaceNone       TrailingSpace = ""
-	SpaceHorizontal TrailingSpace = " "
-	SpaceVertical   TrailingSpace = "\n"
+	SpaceNone           TrailingSpace = ""
+	SpaceHorizontal     TrailingSpace = " "
+	SpaceVertical       TrailingSpace = "\n"
+	SpaceVerticalDouble TrailingSpace = "\n\n"
 )
 
 var ErrNonSpaceCharacter = errors.New("non space character found")
 
-func NewTrailingSpace(s string) (ts TrailingSpace, err error) {
+func NewTrailingSpace(s string, allowMulti bool) (ts TrailingSpace, err error) {
 	var hasHorizontalSpace bool
-	for _, r := range s {
+
+	runes := []rune(s)
+
+	for i, r := range s {
 		if r == '\n' {
+			if allowMulti && i < len(runes)-1 {
+				next := runes[i+1]
+				if next == '\n' {
+					return SpaceVerticalDouble, nil
+				}
+			}
 			return SpaceVertical, nil
 		}
 		if unicode.IsSpace(r) {
@@ -621,7 +631,9 @@ func writeNodes(w io.Writer, level int, nodes []Node, indent bool) error {
 		}
 		// Put a newline after the last node in indentation mode.
 		if indent && ((nextNodeIsBlock(nodes, i) || i == len(nodes)-1) || shouldAlwaysBreakAfter(nodes[i])) {
-			trailing = SpaceVertical
+			if !strings.Contains(string(trailing), string(SpaceVertical)) {
+				trailing = SpaceVertical
+			}
 		}
 		switch trailing {
 		case SpaceNone: