From 5c6cc0f6ce81fe0574b004bf202f95a462c56523 Mon Sep 17 00:00:00 2001
From: Jonathan Desrosiers <desrosj@git.wordpress.org>
Date: Mon, 17 Dec 2018 18:38:13 +0000
Subject: [PATCH] WPDB: Check that `$wpdb->last_result` is countable before
 counting with it.

`wpdb::get_col()` iterates over `$wpdb->last_result`, which can be a non-countable value, should the preceding query have failed.

Props spacedmonkey, desrosj, pento.

Merges [43934] into trunk.

See #45299.

git-svn-id: https://develop.svn.wordpress.org/trunk@44272 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/wp-db.php  | 18 +++++---
 tests/phpunit/tests/db.php | 90 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+), 7 deletions(-)

diff --git a/src/wp-includes/wp-db.php b/src/wp-includes/wp-db.php
index ae08158f64..af42aaf841 100644
--- a/src/wp-includes/wp-db.php
+++ b/src/wp-includes/wp-db.php
@@ -2544,8 +2544,10 @@ class wpdb {
 
 		$new_array = array();
 		// Extract the column values
-		for ( $i = 0, $j = count( $this->last_result ); $i < $j; $i++ ) {
-			$new_array[ $i ] = $this->get_var( null, $x, $i );
+		if ( $this->last_result ) {
+			for ( $i = 0, $j = count( $this->last_result ); $i < $j; $i++ ) {
+				$new_array[ $i ] = $this->get_var( null, $x, $i );
+			}
 		}
 		return $new_array;
 	}
@@ -2585,11 +2587,13 @@ class wpdb {
 		} elseif ( $output == OBJECT_K ) {
 			// Return an array of row objects with keys from column 1
 			// (Duplicates are discarded)
-			foreach ( $this->last_result as $row ) {
-				$var_by_ref = get_object_vars( $row );
-				$key        = array_shift( $var_by_ref );
-				if ( ! isset( $new_array[ $key ] ) ) {
-					$new_array[ $key ] = $row;
+			if ( $this->last_result ) {
+				foreach ( $this->last_result as $row ) {
+					$var_by_ref = get_object_vars( $row );
+					$key        = array_shift( $var_by_ref );
+					if ( ! isset( $new_array[ $key ] ) ) {
+						$new_array[ $key ] = $row;
+					}
 				}
 			}
 			return $new_array;
diff --git a/tests/phpunit/tests/db.php b/tests/phpunit/tests/db.php
index 2fe9df1d47..dbe70b8a6e 100644
--- a/tests/phpunit/tests/db.php
+++ b/tests/phpunit/tests/db.php
@@ -570,6 +570,96 @@ class Tests_DB extends WP_UnitTestCase {
 		$this->assertEquals( 'Walter Sobchak', $row->display_name );
 	}
 
+	/**
+	 * Test the `get_col()` method.
+	 *
+	 * @param string|null        $query       The query to run.
+	 * @param string|array       $expected    The expected resulting value.
+	 * @param arrray|string|null $last_result The value to assign to `$wpdb->last_result`.
+	 * @param int|string         $column      The column index to retrieve.
+	 *
+	 * @dataProvider data_test_get_col
+	 *
+	 * @ticket 45299
+	 */
+	function test_get_col( $query, $expected, $last_result, $column ) {
+		global $wpdb;
+
+		$wpdb->last_result = $last_result;
+
+		$result = $wpdb->get_col( $query, $column );
+
+		if ( $query ) {
+			$this->assertSame( $query, $wpdb->last_query );
+		}
+
+		if ( is_array( $expected ) ) {
+			$this->assertSame( $expected, $result );
+		} else {
+			$this->assertContains( $expected, $result );
+		}
+	}
+
+	/**
+	 * Data provider for testing `get_col()`.
+	 *
+	 * @return array {
+	 *     Arguments for testing `get_col()`.
+	 *
+	 *     @type string|null        $query       The query to run.
+	 *     @type string|array       $expected    The resulting expected value.
+	 *     @type arrray|string|null $last_result The value to assign to `$wpdb->last_result`.
+	 *     @type int|string         $column      The column index to retrieve.
+	 */
+	function data_test_get_col() {
+		global $wpdb;
+
+		return array(
+			array(
+				"SELECT display_name FROM $wpdb->users",
+				'admin',
+				array(),
+				0,
+			),
+			array(
+				"SELECT user_login, user_email FROM $wpdb->users",
+				'admin',
+				array(),
+				0,
+			),
+			array(
+				"SELECT user_login, user_email FROM $wpdb->users",
+				'admin@example.org',
+				array(),
+				1,
+			),
+			array(
+				"SELECT user_login, user_email FROM $wpdb->users",
+				'admin@example.org',
+				array(),
+				'1',
+			),
+			array(
+				"SELECT user_login, user_email FROM $wpdb->users",
+				array( null ),
+				array(),
+				3,
+			),
+			array(
+				'',
+				array(),
+				null,
+				0,
+			),
+			array(
+				null,
+				array(),
+				'',
+				0,
+			),
+		);
+	}
+
 	function test_replace() {
 		global $wpdb;
 		$rows1 = $wpdb->insert( $wpdb->users, array( 'display_name' => 'Walter Sobchak' ) );