Replace negative lookbehind with replacer function for backwards compatibility with Safari.

Author: octet-stream

lib/util/normalizeValue.test.ts

@@ -2,16 +2,22 @@ import test from "ava"
 
 import normalize from "./normalizeValue"
 
-const expected = "First line.\r\nSecond line.\r\nThird line."
+const expected = "\r\nFirst line.\r\nSecond line.\r\nThird line.\r\n"
 
 test("Replaces all CR not followed by LF with CRLF", t => {
-  const actual = normalize("First line.\rSecond line.\rThird line.")
+  const actual = normalize("\rFirst line.\rSecond line.\rThird line.\r")
 
   t.is(actual, expected)
 })
 
 test("Replaces all LF not predicessed by CR with CRLF", t => {
-  const actual = normalize("First line.\nSecond line.\nThird line.")
+  const actual = normalize("\nFirst line.\nSecond line.\nThird line.\n")
+
+  t.is(actual, expected)
+})
+
+test("Replaces all CR or LF characters in a string", t => {
+  const actual = normalize("\rFirst line.\nSecond line.\rThird line.\n")
 
   t.is(actual, expected)
 })

lib/util/normalizeValue.ts

@@ -8,6 +8,15 @@
  * @api private
  */
 const normalizeValue = (value: unknown): string => String(value)
-  .replace(/\r(?!\n)|(?<!\r)\n/g, "\r\n")
+  .replace(/\r|\n/g, (match: string, i: number, str: string) => {
+    if (
+      (match === "\r" && str[i + 1] !== "\n")
+        || (match === "\n" && str[i - 1] !== "\r")
+    ) {
+      return "\r\n"
+    }
+
+    return match
+  })
 
 export default normalizeValue