Pass test for consecutive unnecessarily escaped characters in strings

See #1575 (comment)

This looping is hacky. We might be able to emulate lookbehind instead.

src/printer.js

@@ -3859,10 +3859,6 @@ function makeString(rawContent, enclosingQuote) {
   // Matches _any_ escape and unescaped quotes (both single and double).
   const regex = /\\([\s\S])|(['"])/g;
 
-  // Matches any unnecessarily escaped character.
-  // Adapted from https://github.com/eslint/eslint/blob/de0b4ad7bd820ade41b1f606008bea68683dc11a/lib/rules/no-useless-escape.js#L27
-  const regexUnnecessaryStringEscapes = /((?:^|[^\\])(?:\\\\)*)\\([^\\nrvtbfux\r\n\u2028\u2029"'0-7])/g;
-
   // Escape and unescape single and double quotes as needed to be able to
   // enclose `rawContent` with `enclosingQuote`.
   const newContent = rawContent.replace(regex, (match, escaped, quote) => {
@@ -3882,11 +3878,25 @@ function makeString(rawContent, enclosingQuote) {
 
     // Otherwise return the escape or unescaped quote as-is.
     return match;
-  })
-  // Unescape unnecessarily escaped characters.
-  .replace(regexUnnecessaryStringEscapes, (match, prev, escaped) => prev + escaped);
+  });
+
+  // Matches any unnecessarily escaped character.
+  // Adapted from https://github.com/eslint/eslint/blob/de0b4ad7bd820ade41b1f606008bea68683dc11a/lib/rules/no-useless-escape.js#L27
+  const regexUnnecessaryStringEscapes = /((?:^|[^\\])(?:\\\\)*)\\([^\\nrvtbfux\r\n\u2028\u2029"'0-7])/g;
+
+  let minimallyEscapedContent = newContent;
+  let minimallyEscapedContentPrev;
+
+  while (minimallyEscapedContent !== minimallyEscapedContentPrev) {
+    minimallyEscapedContentPrev = minimallyEscapedContent;
+    // Unescape unnecessarily escaped characters.
+    minimallyEscapedContent = minimallyEscapedContentPrev.replace(
+      regexUnnecessaryStringEscapes,
+      (match, prev, escaped) => prev + escaped
+    );
+  }
 
-  return enclosingQuote + newContent + enclosingQuote;
+  return enclosingQuote + minimallyEscapedContent + enclosingQuote;
 }
 
 function printRegex(node) {