PHPLIB-285: Do not convert count's hint document to a string

docs/includes/apiargs-MongoDBCollection-method-count-option.yaml

@@ -6,8 +6,13 @@ arg_name: option
 name: hint
 type: string|array|object
 description: |
-  The index to use. If you specify a document, it is interpreted as an index
-  specification from which a name will be derived.
+  The index to use. Specify either the index name as a string or the index key
+  pattern as a document. If specified, then the query system will only consider
+  plans using the hinted index.
+
+  .. versionchanged:: 1.2
+     If a document is provided, it is passed to the command as-is. Previously,
+     the library would convert the key pattern to an index name.
 interface: phpmethod
 operation: ~
 optional: true

src/Operation/Count.php

@@ -53,8 +53,9 @@ class Count implements Executable
      *    This is not supported for server versions < 3.4 and will result in an
      *    exception at execution time if used.
      *
-     *  * hint (string|document): The index to use. If a document, it will be
-     *    interpretted as an index specification and a name will be generated.
+     *  * hint (string|document): The index to use. Specify either the index
+     *    name as a string or the index key pattern as a document. If specified,
+     *    then the query system will only consider plans using the hinted index.
      *
      *  * limit (integer): The maximum number of documents to count.
      *
@@ -87,14 +88,8 @@ class Count implements Executable
             throw InvalidArgumentException::invalidType('"collation" option', $options['collation'], 'array or object');
         }
 
-        if (isset($options['hint'])) {
-            if (is_array($options['hint']) || is_object($options['hint'])) {
-                $options['hint'] = \MongoDB\generate_index_name($options['hint']);
-            }
-
-            if ( ! is_string($options['hint'])) {
-                throw InvalidArgumentException::invalidType('"hint" option', $options['hint'], 'string or array or object');
-            }
+        if (isset($options['hint']) && ! is_string($options['hint']) && ! is_array($options['hint']) && ! is_object($options['hint'])) {
+            throw InvalidArgumentException::invalidType('"hint" option', $options['hint'], 'string or array or object');
         }
 
         if (isset($options['limit']) && ! is_integer($options['limit'])) {
@@ -177,7 +172,11 @@ class Count implements Executable
             $cmd['collation'] = (object) $this->options['collation'];
         }
 
-        foreach (['hint', 'limit', 'maxTimeMS', 'skip'] as $option) {
+        if (isset($this->options['hint'])) {
+            $cmd['hint'] = is_array($this->options['hint']) ? (object) $this->options['hint'] : $this->options['hint'];
+        }
+
+        foreach (['limit', 'maxTimeMS', 'skip'] as $option) {
             if (isset($this->options[$option])) {
                 $cmd[$option] = $this->options[$option];
             }

tests/Operation/CountFunctionalTest.php

@@ -3,6 +3,8 @@
 namespace MongoDB\Tests\Operation;
 
 use MongoDB\Operation\Count;
+use MongoDB\Operation\CreateIndexes;
+use MongoDB\Operation\InsertMany;
 use MongoDB\Tests\CommandObserver;
 use stdClass;
 
@@ -26,4 +28,49 @@ class CountFunctionalTest extends FunctionalTestCase
             }
         );
     }
+
+    public function testHintOption()
+    {
+        if (version_compare($this->getServerVersion(), '2.6.0', '<')) {
+            $this->markTestSkipped('count command does not support "hint" option');
+        }
+
+        $insertMany = new InsertMany($this->getDatabaseName(), $this->getCollectionName(), [
+            ['x' => 1],
+            ['x' => 2],
+            ['y' => 3],
+        ]);
+        $insertMany->execute($this->getPrimaryServer());
+
+        $createIndexes = new CreateIndexes($this->getDatabaseName(), $this->getCollectionName(), [
+            ['key' => ['x' => 1], 'sparse' => true, 'name' => 'sparse_x'],
+            ['key' => ['y' => 1]],
+        ]);
+        $createIndexes->execute($this->getPrimaryServer());
+
+        $hintsUsingSparseIndex = [
+            ['x' => 1],
+            'sparse_x',
+        ];
+
+        /* Per SERVER-22041, the count command in server versions before 3.3.2
+         * may ignore the hint option if its query predicate is empty. */
+        $filter = ['_id' => ['$exists' => true]];
+
+        foreach ($hintsUsingSparseIndex as $hint) {
+            $operation = new Count($this->getDatabaseName(), $this->getCollectionName(), $filter, ['hint' => $hint]);
+            $this->assertEquals(2, $operation->execute($this->getPrimaryServer()));
+        }
+
+        $hintsNotUsingSparseIndex = [
+            ['_id' => 1],
+            ['y' => 1],
+            'y_1',
+        ];
+
+        foreach ($hintsNotUsingSparseIndex as $hint) {
+            $operation = new Count($this->getDatabaseName(), $this->getCollectionName(), $filter, ['hint' => $hint]);
+            $this->assertEquals(3, $operation->execute($this->getPrimaryServer()));
+        }
+    }
 }