Add placeholders to fp wrapper. [closes #1780]

lib/fp/baseConvert.js

@@ -1,5 +1,6 @@
 var mapping = require('./mapping.js'),
-    mutateMap = mapping.mutate;
+    mutateMap = mapping.mutate,
+    placeholder = {};
 
 /**
  * The base implementation of `convert` which accepts a `util` object of methods
@@ -176,7 +177,12 @@ function baseConvert(util, name, func) {
       });
       return !result;
     });
-    return result || func;
+
+    result || (result = func);
+    if (mapping.placeholder[name]) {
+      result.placeholder = placeholder;
+    }
+    return result;
   };
 
   if (!isLib) {

lib/fp/mapping.js

@@ -152,6 +152,16 @@ module.exports = {
     }
   },
 
+  /** Used to track methods with placeholder support */
+  'placeholder': {
+    'bind': true,
+    'bindKey': true,
+    'curry': true,
+    'curryRight': true,
+    'partial': true,
+    'partialRight': true
+  },
+
   /** Used to track methods that skip `_.rearg`. */
   'skipRearg': {
     'assign': true,

test/test-fp.js

@@ -563,6 +563,20 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('placeholder methods');
+
+  _.forOwn(mapping.placeholder, function(truthy, methodName) {
+    var func = fp[methodName];
+
+    QUnit.test('`_.' + methodName + '` should have a `placeholder` property', function(assert) {
+      assert.expect(1);
+
+      assert.ok(_.isObject(func.placeholder));
+    });
+  });
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('fp.random');
 
   (function() {