Add named capturing groups to regexpToRegexp method

package.json

@@ -72,11 +72,13 @@
     "@size-limit/preset-small-lib": "^2.1.6",
     "@types/jest": "^24.0.22",
     "@types/node": "^12.12.7",
+    "@types/semver": "^7.3.1",
     "husky": "^3.0.9",
     "jest": "^24.9.0",
     "lint-staged": "^9.4.2",
     "prettier": "^1.19.1",
     "rimraf": "^3.0.0",
+    "semver": "^7.3.2",
     "ts-jest": "^24.1.0",
     "tslint": "^5.20.1",
     "tslint-config-prettier": "^1.18.0",

src/index.spec.ts

@@ -1,5 +1,6 @@
 import * as util from "util";
 import * as pathToRegexp from "./index";
+import { gte } from "semver";
 
 type Test = [
   pathToRegexp.Path,
@@ -2594,6 +2595,95 @@ const TESTS: Test[] = [
   ]
 ];
 
+/**
+ * Named capturing groups (available from Node version 10)
+ */
+if (gte(process.version, "10.0.0")) {
+  TESTS.push(
+    [
+      /\/(?<groupname>.+)/,
+      undefined,
+      [
+        {
+          name: "groupname",
+          prefix: "",
+          suffix: "",
+          modifier: "",
+          pattern: ""
+        }
+      ],
+      [
+        ["/", null],
+        ["/foo", ["/foo", "foo"]]
+      ],
+      []
+    ],
+    [
+      /\/(?<test>.*).(?<format>html|json)/,
+      undefined,
+      [
+        {
+          name: "test",
+          prefix: "",
+          suffix: "",
+          modifier: "",
+          pattern: ""
+        },
+        {
+          name: "format",
+          prefix: "",
+          suffix: "",
+          modifier: "",
+          pattern: ""
+        }
+      ],
+      [
+        ["/route", null],
+        ["/route.txt", null],
+        ["/route.html", ["/route.html", "route", "html"]],
+        ["/route.json", ["/route.json", "route", "json"]]
+      ],
+      []
+    ],
+    [
+      /\/(.+)\/(?<groupname>.+)\/(.+)/,
+      undefined,
+      [
+        {
+          name: 0,
+          prefix: "",
+          suffix: "",
+          modifier: "",
+          pattern: ""
+        },
+        {
+          name: "groupname",
+          prefix: "",
+          suffix: "",
+          modifier: "",
+          pattern: ""
+        },
+        {
+          name: 1,
+          prefix: "",
+          suffix: "",
+          modifier: "",
+          pattern: ""
+        }
+      ],
+      [
+        ["/test", null],
+        ["/test/testData", null],
+        [
+          "/test/testData/extraStuff",
+          ["/test/testData/extraStuff", "test", "testData", "extraStuff"]
+        ]
+      ],
+      []
+    ]
+  );
+}
+
 /**
  * Dynamically generate the entire test suite.
  */

src/index.ts

@@ -453,19 +453,20 @@ export type Token = string | Key;
 function regexpToRegexp(path: RegExp, keys?: Key[]): RegExp {
   if (!keys) return path;
 
-  // Use a negative lookahead to match only capturing groups.
-  const groups = path.source.match(/\((?!\?)/g);
-
-  if (groups) {
-    for (let i = 0; i < groups.length; i++) {
-      keys.push({
-        name: i,
-        prefix: "",
-        suffix: "",
-        modifier: "",
-        pattern: ""
-      });
-    }
+  const groupsRegex = /\((?:\?<(.*?)>)?(?!\?)/g;
+
+  let index = 0;
+  let execResult = groupsRegex.exec(path.source);
+  while (execResult) {
+    keys.push({
+      // Use parenthesized substring match if available, index otherwise
+      name: execResult[1] || index++,
+      prefix: "",
+      suffix: "",
+      modifier: "",
+      pattern: ""
+    });
+    execResult = groupsRegex.exec(path.source);
   }
 
   return path;