Fix Mongo queries with {$regex: /foo/}

The bug manifested as incorrect cursor de-duping, making
queries on different regular expressions "de-dup" into one,
which, combined with hot code reload caused crazy seeming
things such as needing to save twice to see a code change
executed.

packages/mongo-livedata/collection.js

@@ -261,30 +261,44 @@ Meteor.Collection._rewriteSelector = function (selector) {
 
   var ret = {};
   _.each(selector, function (value, key) {
+    // Mongo supports both {field: /foo/} and {field: {$regex: /foo/}}
     if (value instanceof RegExp) {
-      ret[key] = {$regex: value.source};
-      var regexOptions = '';
-      // JS RegExp objects support 'i', 'm', and 'g'. Mongo regex $options
-      // support 'i', 'm', 'x', and 's'. So we support 'i' and 'm' here.
-      if (value.ignoreCase)
-        regexOptions += 'i';
-      if (value.multiline)
-        regexOptions += 'm';
-      if (regexOptions)
-        ret[key].$options = regexOptions;
+      ret[key] = convertRegexpToMongoSelector(value);
+    } else if (value && value.$regex instanceof RegExp) {
+      ret[key] = convertRegexpToMongoSelector(value.$regex);
     }
     else if (_.contains(['$or','$and','$nor'], key)) {
       // Translate lower levels of $and/$or/$nor
       ret[key] = _.map(value, function (v) {
         return Meteor.Collection._rewriteSelector(v);
       });
     }
-    else
+    else {
       ret[key] = value;
+    }
   });
   return ret;
 };
 
+// convert a JS RegExp object to a Mongo {$regex: ..., $options: ...}
+// selector
+var convertRegexpToMongoSelector = function (regexp) {
+  check(regexp, RegExp); // safety belt
+
+  var selector = {$regex: regexp.source};
+  var regexOptions = '';
+  // JS RegExp objects support 'i', 'm', and 'g'. Mongo regex $options
+  // support 'i', 'm', 'x', and 's'. So we support 'i' and 'm' here.
+  if (regexp.ignoreCase)
+    regexOptions += 'i';
+  if (regexp.multiline)
+    regexOptions += 'm';
+  if (regexOptions)
+    selector.$options = regexOptions;
+
+  return selector;
+};
+
 var throwIfSelectorIsNotId = function (selector, methodName) {
   if (!LocalCollection._selectorIsIdPerhapsAsObject(selector)) {
     throw new Meteor.Error(

packages/mongo-livedata/mongo_livedata_tests.js

@@ -876,8 +876,12 @@ if (Meteor.isServer) {
 Tinytest.add('mongo-livedata - rewrite selector', function (test) {
   test.equal(Meteor.Collection._rewriteSelector({x: /^o+B/im}),
              {x: {$regex: '^o+B', $options: 'im'}});
+  test.equal(Meteor.Collection._rewriteSelector({x: {$regex: /^o+B/im}}),
+             {x: {$regex: '^o+B', $options: 'im'}});
   test.equal(Meteor.Collection._rewriteSelector({x: /^o+B/}),
              {x: {$regex: '^o+B'}});
+  test.equal(Meteor.Collection._rewriteSelector({x: {$regex: /^o+B/}}),
+             {x: {$regex: '^o+B'}});
   test.equal(Meteor.Collection._rewriteSelector('foo'),
              {_id: 'foo'});
 
@@ -886,13 +890,15 @@ Tinytest.add('mongo-livedata - rewrite selector', function (test) {
       {'$or': [
         {x: /^o/},
         {y: /^p/},
-        {z: 'q'}
+        {z: 'q'},
+        {w: {$regex: /^r/}}
       ]}
     ),
     {'$or': [
       {x: {$regex: '^o'}},
       {y: {$regex: '^p'}},
-      {z: 'q'}
+      {z: 'q'},
+      {w: {$regex: '^r'}}
     ]}
   );
 
@@ -901,22 +907,28 @@ Tinytest.add('mongo-livedata - rewrite selector', function (test) {
       {'$or': [
         {'$and': [
           {x: /^a/i},
-          {y: /^b/}
+          {y: /^b/},
+          {z: {$regex: /^c/i}},
+          {w: {$regex: '^[abc]', $options: 'i'}} // make sure we don't break vanilla selectors
         ]},
         {'$nor': [
-          {s: /^c/},
-          {t: /^d/i}
+          {s: /^d/},
+          {t: /^e/i},
+          {u: {$regex: /^f/i}}
         ]}
       ]}
     ),
     {'$or': [
       {'$and': [
         {x: {$regex: '^a', $options: 'i'}},
-        {y: {$regex: '^b'}}
+        {y: {$regex: '^b'}},
+        {z: {$regex: '^c', $options: 'i'}},
+        {w: {$regex: '^[abc]', $options: 'i'}}
       ]},
       {'$nor': [
-        {s: {$regex: '^c'}},
-        {t: {$regex: '^d', $options: 'i'}}
+        {s: {$regex: '^d'}},
+        {t: {$regex: '^e', $options: 'i'}},
+        {u: {$regex: '^f', $options: 'i'}}
       ]}
     ]}
   );