feat: More useful TransformerReturnsUnexpectedValueException except…

…ion message.

CHANGELOG.md

@@ -8,6 +8,7 @@
 * feat: Context methods now accept `$context` variable, and pass it to
   exceptions.
 * feat: Main transformer's exception now accepts `$context` variable.
+* feat: More useful `TransformerReturnsUnexpectedValueException` exception message.
 
 ## 0.5.8
 

src/MainTransformer/Exception/TransformerReturnsUnexpectedValueException.php

@@ -16,16 +16,24 @@
 use Rekalogika\Mapper\Context\Context;
 use Rekalogika\Mapper\Exception\UnexpectedValueException;
 use Rekalogika\Mapper\Transformer\Contracts\MixedType;
+use Rekalogika\Mapper\Transformer\Contracts\TransformerInterface;
 use Rekalogika\Mapper\Util\TypeUtil;
 use Symfony\Component\PropertyInfo\Type;
 
 class TransformerReturnsUnexpectedValueException extends UnexpectedValueException
 {
-    public function __construct(Type|MixedType $type, mixed $target, Context $context)
-    {
+    public function __construct(
+        mixed $source,
+        Type|MixedType $targetType,
+        mixed $target,
+        TransformerInterface $transformer,
+        Context $context
+    ) {
         $message = sprintf(
-            'Mapper returns unexpected value. Expected type "%s", but got "%s".',
-            TypeUtil::getTypeString($type),
+            'Trying to map source type "%s" to target type "%s", but the assigned transformer "%s" returns an unexpected type "%s".',
+            \get_debug_type($source),
+            TypeUtil::getTypeString($targetType),
+            \get_class($transformer),
             get_debug_type($target),
         );
 

src/MainTransformer/MainTransformer.php

@@ -172,8 +172,13 @@ public function transform(
                 context: $context
             );
 
-            if (!TypeCheck::isVariableInstanceOf($result, $targetType)) {
-                throw new TransformerReturnsUnexpectedValueException($targetType, $result, context: $context);
+            // check the result type
+
+            if (
+                !TypeCheck::isVariableInstanceOf($result, $targetType)
+                && $result !== null
+            ) {
+                throw new TransformerReturnsUnexpectedValueException($source, $targetType, $result, $transformer, $context);
             }
 
             // if the target type is not null, cache it