Better exception handling

composer.json

@@ -16,6 +16,7 @@
     },
     "require": {
         "php": "^7.2",
+        "ext-json": "*",
         "aws/aws-sdk-php": "^3.91",
         "symfony/property-info": "^4.2"
     },

src/Dynamap.php

@@ -3,6 +3,9 @@
 namespace Dynamap;
 
 use Aws\DynamoDb\DynamoDbClient;
+use Aws\DynamoDb\Exception\DynamoDbException;
+use Dynamap\Exception\ItemNotFound;
+use Dynamap\Exception\TableNotFound;
 
 class Dynamap
 {
@@ -38,16 +41,28 @@ public function getAll(string $table): array
      * Get item by primary key.
      *
      * @param int|string|array $key
-     * @throws \Exception
+     * @throws \InvalidArgumentException If the key is invalid.
+     * @throws ItemNotFound If the item cannot be found.
      */
     public function get(string $table, $key): object
     {
         $tableMapping = $this->mappingObj->getTableMapping($table);
 
-        $item = $this->dynamoDb->getItem([
-            'TableName' => $table,
-            'Key' => $this->buildKeyQuery($key, $tableMapping),
-        ])['Item'];
+        try {
+            $item = $this->dynamoDb->getItem([
+                'TableName' => $table,
+                'Key' => $this->buildKeyQuery($key, $tableMapping),
+            ])['Item'];
+        } catch (DynamoDbException $e) {
+            if ($e->getAwsErrorCode() === 'ResourceNotFoundException') {
+                throw TableNotFound::tableMissingInDynamoDb($table, $e);
+            }
+            throw $e;
+        }
+
+        if ($item === null) {
+            throw ItemNotFound::fromKey($tableMapping->getClassName(), $key);
+        }
 
         return $this->map($item, $table);
     }
@@ -148,14 +163,14 @@ private function map(array $item, string $table): object
 
     /**
      * @param int|string|array $key
-     * @throws \Exception
+     * @throws \InvalidArgumentException
      */
     private function buildKeyQuery($key, TableMapping $tableMapping): array
     {
         $keyQuery = [];
         if (! is_array($key)) {
             if ($tableMapping->isCompositeKey()) {
-                throw new \Exception('The key is a composite key and only a single value was provided');
+                throw new \InvalidArgumentException('The key is a composite key and only a single value was provided');
             }
             foreach ($tableMapping->getKeyMapping() as $fieldMapping) {
                 $keyQuery[$fieldMapping->name()] = $fieldMapping->dynamoDbQueryValue($key);
@@ -164,7 +179,7 @@ private function buildKeyQuery($key, TableMapping $tableMapping): array
             foreach ($tableMapping->getKeyMapping() as $fieldMapping) {
                 $fieldName = $fieldMapping->name();
                 if (! isset($key[$fieldName])) {
-                    throw new \Exception('The key is incomplete');
+                    throw new \InvalidArgumentException('The key is incomplete');
                 }
                 $keyQuery[$fieldName] = $fieldMapping->dynamoDbQueryValue($key[$fieldName]);
             }

src/Exception/ItemNotFound.php

@@ -0,0 +1,14 @@
+<?php declare(strict_types=1);
+
+namespace Dynamap\Exception;
+
+class ItemNotFound extends \Exception
+{
+    /**
+     * @param int|string|array $key
+     */
+    public static function fromKey(string $className, $key): self
+    {
+        return new self("Item `$className` not found for key " . json_encode($key));
+    }
+}

src/Exception/TableNotFound.php

@@ -0,0 +1,19 @@
+<?php declare(strict_types=1);
+
+namespace Dynamap\Exception;
+
+use Aws\DynamoDb\Exception\DynamoDbException;
+
+/**
+ * The table was not found.
+ */
+class TableNotFound extends \Exception
+{
+    public static function tableMissingInDynamoDb(string $table, DynamoDbException $previous): self
+    {
+        $message = "Cannot find the table `$table` in DynamoDB: make sure it exists and that the code has permissions to access it. "
+            . $previous->getAwsErrorMessage();
+
+        return new self($message, 0, $previous);
+    }
+}

src/Mapping.php

@@ -2,6 +2,7 @@
 
 namespace Dynamap;
 
+use Dynamap\Exception\TableNotFound;
 use Symfony\Component\PropertyInfo\Extractor\PhpDocExtractor;
 use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
 use Symfony\Component\PropertyInfo\PropertyInfoExtractor;
@@ -35,6 +36,10 @@ public function __construct(array $mappingConfig)
 
     public function getTableMapping(string $table): TableMapping
     {
+        if (! isset($this->tables[$table])) {
+            throw new TableNotFound("The table `$table` is not configured in Dynamap");
+        }
+
         return $this->tables[$table];
     }
 
@@ -46,6 +51,6 @@ public function getTableFromClassName(string $className): TableMapping
             }
         }
 
-        throw new \Exception("No table mapping for for class $className");
+        throw new TableNotFound("No table mapping found for class `$className`");
     }
 }

tests/DynamapTest.php

@@ -5,6 +5,8 @@
 use Aws\DynamoDb\DynamoDbClient;
 use Aws\DynamoDb\Exception\DynamoDbException;
 use Dynamap\Dynamap;
+use Dynamap\Exception\ItemNotFound;
+use Dynamap\Exception\TableNotFound;
 use Dynamap\Test\Fixture\Article;
 use PHPUnit\Framework\TestCase;
 
@@ -61,6 +63,12 @@ public function setUp(): void
                     'id',
                 ],
             ],
+            'foo' => [ // This is a table that doesn't exist
+                'class' => Article::class,
+                'keys' => [
+                    'id',
+                ],
+            ],
         ];
         $this->dynamap = new Dynamap($dynamoDb, $mapping);
     }
@@ -89,6 +97,30 @@ public function test get all(): void
         $this->assertCount(3, $this->dynamap->getAll('articles'));
     }
 
+    public function test get unknown object(): void
+    {
+        $this->expectException(ItemNotFound::class);
+        $this->expectExceptionMessage('Item `Dynamap\Test\Fixture\Article` not found for key 123');
+
+        $this->dynamap->get('articles', 123);
+    }
+
+    public function test get table that is mapped but doesnt exist in DynamoDB(): void
+    {
+        $this->expectException(TableNotFound::class);
+        $this->expectExceptionMessage('Cannot find the table `foo` in DynamoDB: make sure it exists and that the code has permissions to access it');
+
+        $this->dynamap->get('foo', 123);
+    }
+
+    public function test get unknown table(): void
+    {
+        $this->expectException(TableNotFound::class);
+        $this->expectExceptionMessage('The table `bar` is not configured in Dynamap');
+
+        $this->dynamap->get('bar', 123);
+    }
+
     public function test string attribute(): void
     {
         $article = new Article(123);