Optimizer: fix \{, \} and \- unescpae

Author: DmitrySoshnikov

src/optimizer/transforms/__tests__/char-escape-unescape-transform-test.js

@@ -18,17 +18,17 @@ describe('\e -> e', () => {
   });
 
   it('preserve escape', () => {
-    const re = transform(/\*\^\$\(\)\[/, [
+    const re = transform(/\*\^\$\(\)\[\{\}/, [
       charUnescape,
     ]);
-    expect(re.toString()).toBe(/\*\^\$\(\)\[/.toString());
+    expect(re.toString()).toBe(/\*\^\$\(\)\[\{\}/.toString());
   });
 
   it('char class', () => {
-    const re = transform(/[\e\*\(\]\ \^\$]\(\n/, [
+    const re = transform(/[\e\*\(\]\ \^\$\-]\(\n/, [
       charUnescape,
     ]);
-    expect(re.toString()).toBe(/[e*(\] ^$]\(\n/.toString());
+    expect(re.toString()).toBe(/[e*(\] ^$\-]\(\n/.toString());
   });
 
 });

src/optimizer/transforms/char-escape-unescape-transform.js

@@ -38,12 +38,18 @@ function shouldUnescape(path) {
 }
 
 /**
- * \], \\
+ * \], \\, \-
+ *
+ * Note: \- always preserved to avoid `[a\-z]` turning into `[a-z]`.
+ * TODO: more sophisticated analisys.
  */
 function preservesInCharClass(value) {
-  return /[\]\\]/.test(value);
+  return /[\]\\\\-]/.test(value);
 }
 
+// Note: \{ and \} are always preserved to avoid `a\{2\}` turning
+// into `a{2}`. TODO: more sophisticated analisys.
+
 function preservesEscape(value) {
-  return /[*\[\]()+?^$.\/\\]/.test(value);
+  return /[*\[\]()+?^$.\/\\\{\}]/.test(value);
 }