Ensure fp key methods provide the key argument to their iteratees. [closes #1842]

lib/fp/baseConvert.js

@@ -40,21 +40,16 @@ function baseConvert(util, name, func) {
       keys = _.keys,
       rearg = _.rearg;
 
-  var baseAry = function(func, n) {
-    return function() {
-      var args = arguments,
-          length = Math.min(args.length, n);
+  var baseArity = function(func, n) {
+    return n == 2
+      ? function(a, b) { return func.apply(undefined, arguments); }
+      : function(a) { return func.apply(undefined, arguments); };
+  };
 
-      switch (length) {
-        case 1: return func(args[0]);
-        case 2: return func(args[0], args[1]);
-      }
-      args = Array(length);
-      while (length--) {
-        args[length] = arguments[length];
-      }
-      return func.apply(undefined, args);
-    };
+  var baseAry = function(func, n) {
+    return n == 2
+      ? function(a, b) { return func(a, b); }
+      : function(a) { return func(a); };
   };
 
   var cloneArray = function(array) {
@@ -83,6 +78,13 @@ function baseConvert(util, name, func) {
     });
   };
 
+  var iterateeRearg = function(func, indexes) {
+    return overArg(func, function(func) {
+      var n = indexes.length;
+      return baseArity(rearg(baseAry(func, n), indexes), n);
+    });
+  };
+
   var overArg = function(func, iteratee, retArg) {
     return function() {
       var length = arguments.length,
@@ -172,6 +174,10 @@ function baseConvert(util, name, func) {
           if (n) {
             result = iterateeAry(result, n);
           }
+          var indexes = mapping.iterateeRearg[name];
+          if (indexes) {
+            result = iterateeRearg(result, indexes);
+          }
           if (cap > 1) {
             result = curry(result, cap);
           }

lib/fp/mapping.js

@@ -102,23 +102,30 @@ module.exports = {
     3:[
         'assignInWith', 'assignWith', 'clamp', 'differenceBy', 'differenceWith',
         'getOr', 'inRange', 'intersectionBy', 'intersectionWith', 'isEqualWith',
-        'isMatchWith', 'mergeWith', 'pullAllBy', 'reduce',
-        'reduceRight', 'replace', 'set', 'slice', 'sortedIndexBy', 'sortedLastIndexBy',
-        'transform', 'unionBy', 'unionWith', 'xorBy', 'xorWith', 'zipWith'
+        'isMatchWith', 'mergeWith', 'pullAllBy', 'reduce', 'reduceRight', 'replace',
+        'set', 'slice', 'sortedIndexBy', 'sortedLastIndexBy', 'transform', 'unionBy',
+        'unionWith', 'xorBy', 'xorWith', 'zipWith'
       ],
     4:[
         'fill', 'setWith'
       ]
   },
 
-  /** Used to map ary to rearg configs by method ary. */
+  /** Used to map ary to rearg configs. */
   'aryRearg': {
     2: [1, 0],
     3: [2, 1, 0],
     4: [3, 2, 0, 1]
   },
 
-  /** Used to map ary to rearg configs by method names. */
+  /** Used to map method names to iteratee rearg configs. */
+  'iterateeRearg': {
+    'findKey': [1],
+    'findLastKey': [1],
+    'mapKeys': [1]
+  },
+
+  /** Used to map method names to rearg configs. */
   'methodRearg': {
     'clamp': [2, 0, 1],
     'reduce': [2, 0, 1],