fix: LSP multi-line deletions

cmd/templ/lspcmd/proxy/documentcontents.go

@@ -129,31 +129,13 @@ func (d *Document) Delete(fromLine, fromCol, toLine, toCol int) {
 	prefix := d.Lines[fromLine][:fromCol]
 	suffix := d.Lines[toLine][toCol:]
 
-	lens := d.LineLengths()
-	isWithinLine := fromLine == toLine
-	toLineLen := lens[toLine]
-	fromIsWholeLine := (fromCol == 0 && !isWithinLine) || (fromCol == 0 && isWithinLine && toCol == toLineLen)
-	toIsWholeLine := !isWithinLine && toCol == toLineLen
-
-	if isWithinLine {
-		d.Lines[fromLine] = prefix + suffix
-	} else {
-		d.Lines[fromLine] = prefix
-		d.Lines[toLine] = suffix
-	}
-
-	if !isWithinLine {
-		deleteFromLineIndex := fromLine
-		deleteToLineIndex := toLine + 1
-		if !fromIsWholeLine {
-			deleteFromLineIndex++
-		}
-		if !toIsWholeLine {
-			deleteToLineIndex--
-		}
-		d.DeleteLines(deleteFromLineIndex, deleteToLineIndex)
-	}
+	// Delete intermediate lines.
+	deleteFrom := fromLine
+	deleteTo := fromLine + (toLine - fromLine)
+	d.DeleteLines(deleteFrom, deleteTo)
 
+	// Merge the contents of the final line.
+	d.Lines[fromLine] = prefix + suffix
 }
 
 func (d *Document) DeleteLines(i, j int) {

cmd/templ/lspcmd/proxy/documentcontents_test.go

@@ -143,6 +143,63 @@ func TestDocument(t *testing.T) {
 			},
 			expected: "0\n2",
 		},
+		{
+			name:  "Can remove line prefix",
+			start: "abcdef",
+			operations: []func(d *Document){
+				func(d *Document) {
+					d.Apply(&lsp.Range{
+						Start: lsp.Position{
+							Line:      0,
+							Character: 0,
+						},
+						End: lsp.Position{
+							Line:      0,
+							Character: 3,
+						},
+					}, "")
+				},
+			},
+			expected: "def",
+		},
+		{
+			name:  "Can remove line substring",
+			start: "abcdef",
+			operations: []func(d *Document){
+				func(d *Document) {
+					d.Apply(&lsp.Range{
+						Start: lsp.Position{
+							Line:      0,
+							Character: 2,
+						},
+						End: lsp.Position{
+							Line:      0,
+							Character: 3,
+						},
+					}, "")
+				},
+			},
+			expected: "abdef",
+		},
+		{
+			name:  "Can remove line suffix",
+			start: "abcdef",
+			operations: []func(d *Document){
+				func(d *Document) {
+					d.Apply(&lsp.Range{
+						Start: lsp.Position{
+							Line:      0,
+							Character: 4,
+						},
+						End: lsp.Position{
+							Line:      0,
+							Character: 6,
+						},
+					}, "")
+				},
+			},
+			expected: "abcd",
+		},
 		{
 			name:  "Can remove across lines",
 			start: "0\n1\n22",
@@ -163,23 +220,42 @@ func TestDocument(t *testing.T) {
 			expected: "0\n2",
 		},
 		{
-			name:  "Can remove prefix from text",
-			start: "012345",
+			name:  "Can remove part of two lines",
+			start: "Line one\nLine two\nLine three",
 			operations: []func(d *Document){
 				func(d *Document) {
 					d.Apply(&lsp.Range{
 						Start: lsp.Position{
 							Line:      0,
-							Character: 0,
+							Character: 4,
 						},
 						End: lsp.Position{
+							Line:      2,
+							Character: 4,
+						},
+					}, "")
+				},
+			},
+			expected: "Line three",
+		},
+		{
+			name:  "Can remove all lines",
+			start: "0\n1\n2",
+			operations: []func(d *Document){
+				func(d *Document) {
+					d.Apply(&lsp.Range{
+						Start: lsp.Position{
 							Line:      0,
-							Character: 3,
+							Character: 0,
+						},
+						End: lsp.Position{
+							Line:      2,
+							Character: 1,
 						},
 					}, "")
 				},
 			},
-			expected: "345",
+			expected: "",
 		},
 		{
 			name:  "Can replace line prefix",