d2latex: fix latex backslashes doubling

d2parser/parse.go

@@ -1480,12 +1480,6 @@ func (p *parser) parseBlockString() *d2ast.BlockString {
 		}
 
 		if r != endHint {
-			if (bs.Tag == "latex" || bs.Tag == "tex") && r == '\\' {
-				// For LaTeX, where single backslash is common, we escape it so that users don't have to write double the backslashes
-				sb.WriteRune('\\')
-				sb.WriteRune('\\')
-				continue
-			}
 			sb.WriteRune(r)
 			continue
 		}

d2renderers/d2latex/latex.go

@@ -6,6 +6,7 @@ import (
 	"math"
 	"regexp"
 	"strconv"
+	"strings"
 
 	"oss.terrastruct.com/d2/lib/jsrunner"
 	"oss.terrastruct.com/util-go/xdefer"
@@ -28,6 +29,7 @@ var svgRe = regexp.MustCompile(`<svg[^>]+width="([0-9\.]+)ex" height="([0-9\.]+)
 
 func Render(s string) (_ string, err error) {
 	defer xdefer.Errorf(&err, "latex failed to parse")
+	s = doubleBackslashes(s)
 	runner := jsrunner.NewJSRunner()
 
 	if _, err := runner.RunString(polyfillsJS); err != nil {
@@ -82,3 +84,15 @@ func Measure(s string) (width, height int, err error) {
 
 	return int(math.Ceil(wf * float64(pxPerEx))), int(math.Ceil(hf * float64(pxPerEx))), nil
 }
+
+func doubleBackslashes(s string) string {
+	var result strings.Builder
+	for i := 0; i < len(s); i++ {
+		if s[i] == '\\' {
+			result.WriteString("\\\\")
+		} else {
+			result.WriteByte(s[i])
+		}
+	}
+	return result.String()
+}

e2etests/testdata/txtar/single-backslash-latex/dagre/board.exp.json

@@ -81,7 +81,7 @@
       "fields": null,
       "methods": null,
       "columns": null,
-      "label": "\\\\begin{equation} \\\\label{eq1}\n\\\\begin{split}\nA & = \\\\frac{\\\\\\\\pi r^2}{2} \\\\\\\\\n & = \\\\frac{1}{2} \\\\pi r^2\n\\\\end{split}\n\\\\end{equation}",
+      "label": "\\begin{equation} \\label{eq1}\n\\begin{split}\nA & = \\frac{\\\\pi r^2}{2} \\\\\n & = \\frac{1}{2} \\pi r^2\n\\end{split}\n\\end{equation}",
       "fontSize": 16,
       "fontFamily": "DEFAULT",
       "language": "latex",

e2etests/testdata/txtar/single-backslash-latex/elk/board.exp.json

@@ -81,7 +81,7 @@
       "fields": null,
       "methods": null,
       "columns": null,
-      "label": "\\\\begin{equation} \\\\label{eq1}\n\\\\begin{split}\nA & = \\\\frac{\\\\\\\\pi r^2}{2} \\\\\\\\\n & = \\\\frac{1}{2} \\\\pi r^2\n\\\\end{split}\n\\\\end{equation}",
+      "label": "\\begin{equation} \\label{eq1}\n\\begin{split}\nA & = \\frac{\\\\pi r^2}{2} \\\\\n & = \\frac{1}{2} \\pi r^2\n\\end{split}\n\\end{equation}",
       "fontSize": 16,
       "fontFamily": "DEFAULT",
       "language": "latex",