Support join on expressions (#47)

src/Query/JoinClause.php

@@ -127,19 +127,19 @@ public function using(...$columns): self
     /**
      * Set "on" clause for join.
      *
-     * @param string $first
-     * @param string $operator
-     * @param string $second
-     * @param string $concatOperator
+     * @param string|Expression $first
+     * @param string            $operator
+     * @param string|Expression $second
+     * @param string            $concatOperator
      *
      * @return JoinClause
      */
-    public function on(string $first, string $operator, string $second, string $concatOperator = Operator::AND): self
+    public function on($first, string $operator, $second, string $concatOperator = Operator::AND): self
     {
         $expression = (new TwoElementsLogicExpression($this->query))
-            ->firstElement(new Identifier($first))
+            ->firstElement(is_string($first) ? new Identifier($first) : $first)
             ->operator($operator)
-            ->secondElement(new Identifier($second))
+            ->secondElement(is_string($second) ? new Identifier($second) : $second)
             ->concatOperator($concatOperator);
 
         $this->onClauses[] = $expression;

tests/BuilderTest.php

@@ -1175,6 +1175,12 @@ public function testJoinWithOnClause()
             $join->table('table2')->on('column_from_table_1', '=', 'column_from_table_2');
         });
         $this->assertEquals('SELECT * FROM `table1` ANY LEFT JOIN `table2` ON `column_from_table_1` = `column_from_table_2`', $builder->toSql());
+
+        $builder = $this->getBuilder();
+        $builder->from('table1')->anyLeftJoin(function (JoinClause $join) {
+            $join->table('table2')->on('column_from_table_1', '=', raw('toUInt32(`column_from_table_2`)'));
+        });
+        $this->assertEquals('SELECT * FROM `table1` ANY LEFT JOIN `table2` ON `column_from_table_1` = toUInt32(`column_from_table_2`)', $builder->toSql());
     }
 
     public function testMultipleJoins()