Returns null in AlterTable methods where callables do nothing

Author: natanfelles

src/Definition/AlterTable.php

@@ -186,7 +186,7 @@ protected function renderAdd() : ?string
         }
         $definition = new TableDefinition($this->database);
         $this->sql['add']($definition);
-        return $definition->sql('ADD');
+        return $definition->sql('ADD') ?: null;
     }
 
     /**
@@ -207,7 +207,7 @@ protected function renderChange() : ?string
         }
         $definition = new TableDefinition($this->database);
         $this->sql['change']($definition);
-        return $definition->sql('CHANGE');
+        return $definition->sql('CHANGE') ?: null;
     }
 
     /**
@@ -228,7 +228,7 @@ protected function renderModify() : ?string
         }
         $definition = new TableDefinition($this->database);
         $this->sql['modify']($definition);
-        return $definition->sql('MODIFY');
+        return $definition->sql('MODIFY') ?: null;
     }
 
     public function dropColumn(string $name, bool $ifExists = false) : static

tests/Definition/AlterTableTest.php

@@ -67,6 +67,17 @@ public function testAdd() : void
         );
     }
 
+    public function testAddEmpty() : void
+    {
+        $sql = $this->alterTable->table('t1')
+            ->add(static function (TableDefinition $definition) : void {
+            });
+        self::assertSame(
+            "ALTER TABLE `t1`\n",
+            $sql->sql()
+        );
+    }
+
     public function testChange() : void
     {
         $sql = $this->alterTable->table('t1')
@@ -79,6 +90,17 @@ public function testChange() : void
         );
     }
 
+    public function testChangeEmpty() : void
+    {
+        $sql = $this->alterTable->table('t1')
+            ->change(static function (TableDefinition $definition) : void {
+            });
+        self::assertSame(
+            "ALTER TABLE `t1`\n",
+            $sql->sql()
+        );
+    }
+
     public function testModify() : void
     {
         $sql = $this->alterTable->table('t1')
@@ -91,6 +113,17 @@ public function testModify() : void
         );
     }
 
+    public function testModifyEmpty() : void
+    {
+        $sql = $this->alterTable->table('t1')
+            ->modify(static function (TableDefinition $definition) : void {
+            });
+        self::assertSame(
+            "ALTER TABLE `t1`\n",
+            $sql->sql()
+        );
+    }
+
     public function testDropColumnIfExists() : void
     {
         $alterTable = $this->alterTable->table('t1')->dropColumnIfExists('foo');