Fix how inputs for elements nested in collections are merged

src/Form.php

@@ -792,6 +792,19 @@ public function attachInputFilterDefaults(InputFilterInterface $inputFilter, Fie
                         $inputFilter->replace($input, $name);
                         continue;
                     }
+
+                    // If we are dealing with a collection input filter, check
+                    // the input filter it composes for an element of the same
+                    // name as was done above.
+                    if ($inputFilter instanceof CollectionInputFilter
+                        && $inputFilter->getInputFilter()->has($name)
+                        && $inputFilter->getInputFilter() instanceof ReplaceableInputInterface
+                    ) {
+                        $collectionInputFilter = $inputFilter->getInputFilter();
+                        $input->merge($collectionInputFilter->get($name));
+                        $collectionInputFilter->replace($input, $name);
+                        continue;
+                    }
                 }
 
                 // Add element input filter to CollectionInputFilter

test/Integration/FormCreatesCollectionInputFilterTest.php

@@ -0,0 +1,81 @@
+<?php
+/**
+ * @see       https://github.com/zendframework/zend-form for the canonical source repository
+ * @copyright Copyright (c) 2017 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license   https://github.com/zendframework/zend-form/blob/master/LICENSE.md New BSD License
+ */
+
+namespace ZendTest\Form\Integration;
+
+use PHPUnit_Framework_TestCase as TestCase;
+use Zend\Form\Form;
+use Zend\Form\InputFilterProviderFieldset;
+use Zend\Validator;
+
+class FormCreatesCollectionInputFilterTest extends TestCase
+{
+    public static function assertValidatorFound($class, array $validators, $message = null)
+    {
+        $message = $message ?: sprintf('Failed to find validator of type %s in validator list', $class);
+        foreach ($validators as $instance) {
+            $validator = $instance['instance'];
+            if ($validator instanceof $class) {
+                return true;
+            }
+        }
+        var_export($validators);
+        self::fail($message);
+    }
+
+    /**
+     * @see https://github.com/zendframework/zend-form/issues/78
+     */
+    public function testCollectionInputFilterContainsExpectedValidators()
+    {
+        $form = new Form;
+        $form->add([
+            'name' => 'collection',
+            'type' => 'collection',
+            'options' => [
+                'target_element' => [
+                    'type' => InputFilterProviderFieldset::class,
+                    'elements' => [
+                        [
+                            'spec' => [
+                                'name' => 'date',
+                                'type' => 'date'
+                            ],
+                        ],
+                    ],
+                    'options' => ['input_filter_spec' => [
+                        'date' => [
+                            'required' => false,
+                            'validators' => [
+                                ['name' => 'StringLength'],
+                            ],
+                        ],
+                    ]],
+                ],
+            ],
+        ]);
+        $inputFilter = $form->getInputFilter();
+        $filter = $inputFilter->get('collection')->getInputFilter()->get('date');
+
+        $validators = $filter->getValidatorChain()->getValidators();
+        $this->assertCount(3, $validators);
+        $this->assertValidatorFound(Validator\StringLength::class, $validators);
+        $this->assertValidatorFound(Validator\Date::class, $validators);
+        $this->assertValidatorFound(Validator\DateStep::class, $validators);
+
+        return $form;
+    }
+
+    /**
+     * @depends testCollectionInputFilterContainsExpectedValidators
+     */
+    public function testCollectionElementDoesNotCreateDiscreteElementInInputFilter(Form $form)
+    {
+        $inputFilter = $form->getInputFilter();
+        $this->assertFalse($inputFilter->has('date'));
+    }
+}