From 58666bc2ce5ec83ae8962092c40a7f971f061738 Mon Sep 17 00:00:00 2001
From: Monroe Ekilah <monroe@ekilah.dev>
Date: Mon, 17 Aug 2020 12:56:57 -0700
Subject: [PATCH 1/5] workaround for broken Edge versions 15-18

---
 src/parsimmon.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/parsimmon.js b/src/parsimmon.js
index 028f701..c4ff4b1 100644
--- a/src/parsimmon.js
+++ b/src/parsimmon.js
@@ -695,7 +695,12 @@ function formatError(input, error) {
 
 function flags(re) {
   var s = "" + re;
-  return s.slice(s.lastIndexOf("/") + 1);
+  var fs = s.slice(s.lastIndexOf("/") + 1);
+  if (fs === "undefined") {
+    // MS Edge v15-18 workaround
+    return ""
+  }
+  return fs
 }
 
 function anchoredRegexp(re) {

From cc668ff9599af4e29e89a71312517c92d354ba06 Mon Sep 17 00:00:00 2001
From: Monroe Ekilah <monroe@ekilah.dev>
Date: Mon, 17 Aug 2020 14:33:47 -0700
Subject: [PATCH 2/5] use .flags when it is present

---
 src/parsimmon.js | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/parsimmon.js b/src/parsimmon.js
index c4ff4b1..6ffea47 100644
--- a/src/parsimmon.js
+++ b/src/parsimmon.js
@@ -694,13 +694,17 @@ function formatError(input, error) {
 }
 
 function flags(re) {
-  var s = "" + re;
-  var fs = s.slice(s.lastIndexOf("/") + 1);
-  if (fs === "undefined") {
-    // MS Edge v15-18 workaround
-    return ""
+  if (re.flags !== undefined) {
+    return re.flags;
   }
-  return fs
+  // legacy browser support
+  return [
+    re.global ? "g" : "",
+    re.ignoreCase ? "i" : "",
+    re.multiline ? "m" : "",
+    re.unicode ? "u" : "",
+    re.sticky ? "y" : "",
+  ].join("");
 }
 
 function anchoredRegexp(re) {

From 9372b12470030d989d3e9a1ab74a0964bef2d658 Mon Sep 17 00:00:00 2001
From: Monroe Ekilah <monroe@ekilah.dev>
Date: Mon, 24 Aug 2020 17:31:38 -0700
Subject: [PATCH 3/5] lint:fix

---
 src/parsimmon.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/parsimmon.js b/src/parsimmon.js
index 6ffea47..3a19356 100644
--- a/src/parsimmon.js
+++ b/src/parsimmon.js
@@ -703,7 +703,7 @@ function flags(re) {
     re.ignoreCase ? "i" : "",
     re.multiline ? "m" : "",
     re.unicode ? "u" : "",
-    re.sticky ? "y" : "",
+    re.sticky ? "y" : ""
   ].join("");
 }
 

From 37b45b17e874211747d6bc900fd7822a44715fbc Mon Sep 17 00:00:00 2001
From: Monroe Ekilah <monroe@ekilah.dev>
Date: Mon, 24 Aug 2020 17:41:54 -0700
Subject: [PATCH 4/5] add test for flags function

---
 src/parsimmon.js        |  1 +
 test/core/flags.test.js | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 test/core/flags.test.js

diff --git a/src/parsimmon.js b/src/parsimmon.js
index 3a19356..8c8c23d 100644
--- a/src/parsimmon.js
+++ b/src/parsimmon.js
@@ -1365,6 +1365,7 @@ Parsimmon.empty = empty;
 Parsimmon.end = end;
 Parsimmon.eof = eof;
 Parsimmon.fail = fail;
+Parsimmon.flags = flags;
 Parsimmon.formatError = formatError;
 Parsimmon.index = index;
 Parsimmon.isParser = isParser;
diff --git a/test/core/flags.test.js b/test/core/flags.test.js
new file mode 100644
index 0000000..819658c
--- /dev/null
+++ b/test/core/flags.test.js
@@ -0,0 +1,21 @@
+"use strict";
+
+testSetScenario(function() {
+  describe("Parsimmon.flags()", function() {
+    it("works in modern browsers", function() {
+      var flags = Parsimmon.flags(/a/gim);
+      assert.strictEqual(flags, "gim");
+    });
+
+    it("works on legacy browsers without Regexp.flags property", function() {
+      var oldRegExp = /a/gim;
+
+      // Simulate old RegExp without the flags property
+      Object.defineProperty(oldRegExp, "flags", { value: undefined });
+      assert.strictEqual(oldRegExp.flags, undefined);
+
+      var flags = Parsimmon.flags(oldRegExp);
+      assert.strictEqual(flags, "gim");
+    });
+  });
+});

From 0577c93c6562a38e2b0d1b7c4291fea071bae071 Mon Sep 17 00:00:00 2001
From: Monroe Ekilah <monroe@ekilah.dev>
Date: Mon, 24 Aug 2020 18:08:08 -0700
Subject: [PATCH 5/5] 100% test coverage

---
 test/.eslintrc          |  3 +++
 test/core/flags.test.js | 24 +++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/test/.eslintrc b/test/.eslintrc
index 4c7229e..cc00932 100644
--- a/test/.eslintrc
+++ b/test/.eslintrc
@@ -7,5 +7,8 @@
     "Parsimmon": true,
     "assert": true,
     "testSetScenario": true
+  },
+  "rules": {
+    "no-invalid-regexp": ["error", {"allowConstructorFlags": ["u", "y"]}]
   }
 }
diff --git a/test/core/flags.test.js b/test/core/flags.test.js
index 819658c..7500ad2 100644
--- a/test/core/flags.test.js
+++ b/test/core/flags.test.js
@@ -3,19 +3,33 @@
 testSetScenario(function() {
   describe("Parsimmon.flags()", function() {
     it("works in modern browsers", function() {
-      var flags = Parsimmon.flags(/a/gim);
-      assert.strictEqual(flags, "gim");
+      // eslint-disable-next-line no-invalid-regexp
+      var flags = Parsimmon.flags(new RegExp("a", "gimuy"));
+      assert.strictEqual(flags, "gimuy");
     });
 
-    it("works on legacy browsers without Regexp.flags property", function() {
-      var oldRegExp = /a/gim;
+    it("works on legacy browsers without Regexp.flags property with flags", function() {
+      // eslint-disable-next-line no-invalid-regexp
+      var oldRegExp = new RegExp("a", "gimuy");
 
       // Simulate old RegExp without the flags property
       Object.defineProperty(oldRegExp, "flags", { value: undefined });
       assert.strictEqual(oldRegExp.flags, undefined);
 
       var flags = Parsimmon.flags(oldRegExp);
-      assert.strictEqual(flags, "gim");
+      assert.strictEqual(flags, "gimuy");
+    });
+
+    it("works on legacy browsers without Regexp.flags property without flags", function() {
+      // eslint-disable-next-line no-invalid-regexp
+      var oldRegExp = new RegExp("a", "");
+
+      // Simulate old RegExp without the flags property
+      Object.defineProperty(oldRegExp, "flags", { value: undefined });
+      assert.strictEqual(oldRegExp.flags, undefined);
+
+      var flags = Parsimmon.flags(oldRegExp);
+      assert.strictEqual(flags, "");
     });
   });
 });