Adding __toString object support

Author: mtdowling

src/FnDispatcher.php

@@ -213,7 +213,17 @@ private function fn_type(array $args)
     private function fn_to_string(array $args)
     {
         $this->validateArity('to_string', count($args), 1);
-        return is_string($args[0]) ? $args[0] : json_encode($args[0]);
+        $v = $args[0];
+        if (is_string($v)) {
+            return $v;
+        } elseif (is_object($v)
+            && !($v instanceof \JsonSerializable)
+            && method_exists($v, '__toString')
+        ) {
+            return (string) $v;
+        }
+
+        return json_encode($v);
     }
 
     private function fn_to_number(array $args)

tests/FnDispatcherTest.php

@@ -0,0 +1,41 @@
+<?php
+namespace JmesPath\Tests;
+
+use JmesPath\FnDispatcher;
+
+class FnDispatcherTest extends \PHPUnit_Framework_TestCase
+{
+    public function testConvertsToString()
+    {
+        $fn = new FnDispatcher();
+        $this->assertEquals('foo', $fn('to_string', ['foo']));
+        $this->assertEquals('1', $fn('to_string', [1]));
+        $this->assertEquals('["foo"]', $fn('to_string', [['foo']]));
+        $std = new \stdClass();
+        $std->foo = 'bar';
+        $this->assertEquals('{"foo":"bar"}', $fn('to_string', [$std]));
+        $this->assertEquals('foo', $fn('to_string', [new _TestStringClass()]));
+        $this->assertEquals('"foo"', $fn('to_string', [new _TestJsonStringClass()]));
+    }
+}
+
+class _TestStringClass
+{
+    public function __toString()
+    {
+        return 'foo';
+    }
+}
+
+class _TestJsonStringClass implements \JsonSerializable
+{
+    public function __toString()
+    {
+        return 'no!';
+    }
+
+    public function jsonSerialize()
+    {
+        return 'foo';
+    }
+}