feat: add rudimentary support for maps

Re: Automattic/mongoose#681

lib/index.js

@@ -69,9 +69,10 @@ exports.get = function (path, o, special, map) {
     if (lookup) {
       obj = lookup(obj, part);
     } else {
-      obj = special && obj[special]
-        ? obj[special][part]
-        : obj[part];
+      var _from = special && obj[special] ? obj[special] : obj;
+      obj = _from instanceof Map ?
+        _from.get(part) :
+        obj[part];
     }
 
     if (!obj) return map(obj);
@@ -134,7 +135,7 @@ exports.unset = function (path, o) {
       delete cur[parts[i]];
       return true;
     }
-    cur = cur[parts[i]];
+    cur = cur instanceof Map ? cur.get(parts[i]) : cur[parts[i]];
   }
 
   return true;
@@ -213,9 +214,10 @@ exports.set = function (path, val, o, special, map, _copying) {
     if (lookup) {
       obj = lookup(obj, part);
     } else {
-      obj = special && obj[special]
-        ? obj[special][part]
-        : obj[part];
+      var _to = special && obj[special] ? obj[special] : obj;
+      obj = _to instanceof Map ?
+        _to.get(part) :
+        _to[part];
     }
 
     if (!obj) return;
@@ -260,6 +262,8 @@ exports.set = function (path, val, o, special, map, _copying) {
   } else {
     if (lookup) {
       lookup(obj, part, map(val));
+    } else if (obj instanceof Map) {
+      obj.set(part, val);
     } else {
       obj[part] = map(val);
     }

test/index.js

@@ -1792,6 +1792,17 @@ describe('mpath', function(){
       done();
     });
 
+    it('underneath a map', function(done) {
+      assert.equal(mpath.get('a.b', { a: new Map([['b', 1]]) }), 1);
+
+      var m = new Map([['b', 1]]);
+      var obj = { a: m };
+      mpath.set('a.c', 2, obj);
+      assert.equal(m.get('c'), 2);
+
+      done();
+    });
+
     it('unset', function(done) {
       var o = { a: 1 };
       mpath.unset('a', o);