Fix price filtering when there are variations.

The price filtering query wasn't working properly when there are
variations with different prices: if at least one variation was
outside of the price range but other were inside, the product wasn't
being listed.

includes/class-wc-query.php

@@ -622,9 +622,9 @@ class WC_Query {
 
 		$args['join']   = $this->append_product_sorting_table_join( $args['join'] );
 		$args['where'] .= $wpdb->prepare(
-			' AND wc_product_meta_lookup.min_price >= %f AND wc_product_meta_lookup.max_price <= %f ',
-			$current_min_price,
-			$current_max_price
+			' AND NOT (%f<wc_product_meta_lookup.min_price OR %f>wc_product_meta_lookup.max_price ) ',
+			$current_max_price,
+			$current_min_price
 		);
 		return $args;
 	}

tests/php/includes/class-wc-query-test.php

@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * Tests for WC_Query.
+ */
+class WC_Query_Test extends \WC_Unit_Test_Case {
+
+	/**
+	 * @testdox 'price_filter_post_clauses' generates the proper 'where' clause when there are 'max_price' and 'min_price' arguments in the query.
+	 */
+	public function test_price_filter_post_clauses_creates_the_proper_where_clause() {
+		// phpcs:disable Squiz.Commenting
+		$wp_query = new class() {
+			public function is_main_query() {
+				return true;
+			}
+		};
+		// phpcs:enable Squiz.Commenting
+
+		$_GET['min_price'] = '100';
+		$_GET['max_price'] = '200';
+
+		$sut = new WC_Query();
+
+		$args = array(
+			'join'  => '(JOIN CLAUSE)',
+			'where' => '(WHERE CLAUSE)',
+		);
+
+		$args     = $sut->price_filter_post_clauses( $args, $wp_query );
+		$expected = '(WHERE CLAUSE) AND NOT (200.000000<wc_product_meta_lookup.min_price OR 100.000000>wc_product_meta_lookup.max_price ) ';
+
+		$this->assertEquals( $expected, $args['where'] );
+	}
+}