Translate HAVING without GROUP BY to "GROUP BY 1 HAVING"

The previous method of translating ungrouped HAVING to "AND" had some problems:

1. If no WHERE was in the query, the query would fail with: `near "AND": syntax error`
2. When an aggregate function was used in having (e.g, COUNT(*) > 1), the query
    would fail with: `misuse of aggregate function COUNT()`

This commit fixes both of these issues.

tests/WP_SQLite_Translator_Tests.php

@@ -3077,6 +3077,56 @@ public function testGroupByHaving() {
 		);
 	}
 
+	public function testHavingWithoutGroupBy() {
+		$this->assertQuery(
+			'CREATE TABLE _tmp_table (
+				name varchar(20)
+			);'
+		);
+
+		$this->assertQuery(
+			"INSERT INTO _tmp_table VALUES ('a'), ('b'), ('b'), ('c'), ('c'), ('c')"
+		);
+
+		// HAVING condition satisfied
+		$result = $this->assertQuery(
+			"SELECT 'T' FROM _tmp_table HAVING COUNT(*) > 1"
+		);
+		$this->assertEquals(
+			array(
+				(object) array(
+					':param0' => 'T',
+				),
+			),
+			$result
+		);
+
+		// HAVING condition not satisfied
+		$result = $this->assertQuery(
+			"SELECT 'T' FROM _tmp_table HAVING COUNT(*) > 100"
+		);
+		$this->assertEquals(
+			array(),
+			$result
+		);
+
+		// DISTINCT ... HAVING, where only some results meet the HAVING condition
+		$result = $this->assertQuery(
+			'SELECT DISTINCT name FROM _tmp_table HAVING COUNT(*) > 1'
+		);
+		$this->assertEquals(
+			array(
+				(object) array(
+					'name' => 'b',
+				),
+				(object) array(
+					'name' => 'c',
+				),
+			),
+			$result
+		);
+	}
+
 	/**
 	 * @dataProvider mysqlVariablesToTest
 	 */

wp-includes/sqlite/class-wp-sqlite-translator.php

@@ -2619,7 +2619,7 @@ private function capture_group_by( $token ) {
 	}
 
 	/**
-	 * Translate WHERE something HAVING something to WHERE something AND something.
+	 * Translate HAVING without GROUP BY to GROUP BY 1 HAVING.
 	 *
 	 * @param WP_SQLite_Token $token The token to translate.
 	 *
@@ -2638,8 +2638,15 @@ private function translate_ungrouped_having( $token ) {
 		if ( $this->has_group_by ) {
 			return false;
 		}
-		$this->rewriter->skip();
-		$this->rewriter->add( new WP_SQLite_Token( 'AND', WP_SQLite_Token::TYPE_KEYWORD ) );
+
+		// GROUP BY is missing, add "GROUP BY 1" before the HAVING clause.
+		$having = $this->rewriter->skip();
+		$this->rewriter->add( new WP_SQLite_Token( ' ', WP_SQLite_Token::TYPE_DELIMITER ) );
+		$this->rewriter->add( new WP_SQLite_Token( 'GROUP BY', WP_SQLite_Token::TYPE_KEYWORD ) );
+		$this->rewriter->add( new WP_SQLite_Token( ' ', WP_SQLite_Token::TYPE_DELIMITER ) );
+		$this->rewriter->add( new WP_SQLite_Token( '1', WP_SQLite_Token::TYPE_NUMBER ) );
+		$this->rewriter->add( new WP_SQLite_Token( ' ', WP_SQLite_Token::TYPE_DELIMITER ) );
+		$this->rewriter->add( $having );
 
 		return true;
 	}