Add limited offset support to mysql_fetch_field()

`mysqli` seems to reuse the result objects and doesn't support this feature directly, making this feature very brittle. It should be avoided.

2 files changed, 174 insertions, 9 deletions

diff --git a/lib/mysql.php b/lib/mysql.php
index 909fdec..7c79210 100644
--- a/lib/mysql.php
+++ b/lib/mysql.php
@@ -411,16 +411,39 @@ namespace {
             return mysqli_fetch_lengths($result);
         }
 
-        function mysql_fetch_field($result) /* : object|*/
+        function mysql_fetch_field($result, $field_offset = null) /* : object|*/
         {
+            static $fields = array();
+
             if (!\Dshafik\MySQL::checkValidResult($result, __FUNCTION__)) {
                 // @codeCoverageIgnoreStart
                 return false;
                 // @codeCoverageIgnoreEnd
             }
-            $res = mysqli_fetch_field($result);
-            if ($res === false) {
+
+            $result_hash = spl_object_hash($result);
+            if ($field_offset === null) {
+                $fields[$result_hash][] = true;
+                $res = mysqli_fetch_field($result);
+            } elseif ($field_offset > mysqli_num_fields($result)) {
                 trigger_error('mysql_fetch_field(): Bad field offset', E_USER_WARNING);
+                return false;
+            } else {
+                $i = 0;
+                if (isset($fields[$result_hash])) {
+                    $i = count($fields[$result_hash]);
+                }
+
+                while ($i <= $field_offset) {
+                    $res = mysqli_fetch_field($result);
+
+                    if ($res === false) {
+                        return false;
+                    }
+
+                    $fields[$result_hash][$i] = true;
+                    $i++;
+                }  
             }
 
             if ($res instanceof \stdClass) {
diff --git a/tests/MySqlShimTest.php b/tests/MySqlShimTest.php
index 875c5ed..a16f2c9 100644
--- a/tests/MySqlShimTest.php
+++ b/tests/MySqlShimTest.php
@@ -519,7 +519,7 @@ class MySqlShimTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
         $this->assertEquals('testing', mysql_field_table($result, 10));
         $this->assertEquals('ten', mysql_field_name($result, 10));
         $this->assertEquals('string', mysql_field_type($result, 10));
-        $this->assertEquals(35, mysql_field_len($result, 10));
+        $this->assertEquals(52, mysql_field_len($result, 10));
         $this->assertEquals('set', mysql_field_flags($result, 10));
 
         $this->assertEquals('testing', mysql_field_table($result, 11));
@@ -597,7 +597,7 @@ class MySqlShimTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
         $this->assertEquals('testing', mysql_field_table($result, 10));
         $this->assertEquals('ten', mysql_field_name($result, 10));
         $this->assertEquals('string', mysql_field_type($result, 10));
-        $this->assertEquals(35*3, mysql_field_len($result, 10));
+        $this->assertEquals(156, mysql_field_len($result, 10));
         $this->assertEquals('set', mysql_field_flags($result, 10));
 
         $this->assertEquals('testing', mysql_field_table($result, 11));
@@ -960,7 +960,7 @@ class MySqlShimTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
         $this->assertEquals('information_schema', mysql_db_name($dbs, 0));
     }
 
-    public function test_mysql_fetch_field()
+    public function test_mysql_fetch_field_with_offset()
     {
         $this->getConnection();
 
@@ -1048,6 +1048,149 @@ class MySqlShimTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
         }
     }
 
+    public function test_mysql_fetch_field_with_nonconsecutive_offset()
+    {
+        $this->getConnection();
+
+        $result = mysql_query(
+            "INSERT INTO
+                testing (one, two, three, four, five, six, seven, eight, nine, ten, eleven)
+             VALUES
+                ('eight', '8', '8', '8', '8', '8', '8', '8', 'eight', 'eight', '8')"
+        );
+        $this->assertTrue($result);
+
+        $result = mysql_unbuffered_query("SELECT * FROM testing WHERE one = 'eight' LIMIT 1");
+        $this->assertNotFalse($result);
+
+        $row = mysql_fetch_assoc($result);
+
+        $map = array(
+            1 => array(
+                'name' => 'one', 'max_length' => 5, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 1, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            3 => array(
+                'name' => 'three', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 1, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            6 => array(
+                'name' => 'six', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            10 => array(
+                'name' => 'ten', 'max_length' => 5, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            11 => array(
+                'name' => 'eleven', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 1,
+                'type' => 'blob', 'unsigned' => 0, 'zerofill' => 0
+            ),
+        );
+
+        foreach ($map as $index => $values) {
+            $field = mysql_fetch_field($result, $index);
+            $this->assertInstanceOf(\stdClass::class, $field);
+
+            foreach ($values as $key => $value) {
+                $this->assertEquals($field->{$key}, $value, "Field '$index:$key' doesn't match.  Expected: $value, Actual: {$field->{$key}}");
+            }
+        }
+    }
+
+    public function test_mysql_fetch_field_without_offset()
+    {
+        $this->getConnection();
+
+        $result = mysql_query(
+            "INSERT INTO
+                testing (one, two, three, four, five, six, seven, eight, nine, ten, eleven)
+             VALUES
+                ('seven', '7', '7', '7', '7', '7', '7', '7', 'seven', 'seven', '7')"
+        );
+        $this->assertTrue($result, mysql_error());
+
+        $result = mysql_query("SELECT * FROM testing WHERE one = 'seven' LIMIT 1");
+        $this->assertNotFalse($result);
+
+        $map = array(
+            0 => array(
+                'name' => 'id', 'max_length' => 1, 'not_null' => 1, 'primary_key' => 1,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 1, 'blob' => 0,
+                'type' => 'int', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            1 => array(
+                'name' => 'one', 'max_length' => 5, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 1, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            2 => array(
+                'name' => 'two', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 1, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            3 => array(
+                'name' => 'three', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 1, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            4 => array(
+                'name' => 'four', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 1, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            5 => array(
+                'name' => 'five', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            6 => array(
+                'name' => 'six', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            7 => array(
+                'name' => 'seven', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 1, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            8 => array(
+                'name' => 'eight', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            9 => array(
+                'name' => 'nine', 'max_length' => 5, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            10 => array(
+                'name' => 'ten', 'max_length' => 5, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 0,
+                'type' => 'string', 'unsigned' => 0, 'zerofill' => 0
+            ),
+            11 => array(
+                'name' => 'eleven', 'max_length' => 1, 'not_null' => 0, 'primary_key' => 0,
+                'unique_key' => 0, 'multiple_key' => 0, 'numeric' => 0, 'blob' => 1,
+                'type' => 'blob', 'unsigned' => 0, 'zerofill' => 0
+            ),
+        );
+
+        foreach ($map as $index => $values) {
+            $field = mysql_fetch_field($result);
+            $this->assertInstanceOf(\stdClass::class, $field);
+
+            foreach ($values as $key => $value) {
+                $this->assertEquals($field->{$key}, $value, "Field '$index:$key' doesn't match.  Expected: $value, Actual: {$field->{$key}}");
+            }
+        }
+    }
+
     public function test_mysql_fetch_field_fail_false()
     {
         $this->expectWarning();
@@ -1074,7 +1217,6 @@ class MySqlShimTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
         $result = mysql_query("SELECT one FROM testing WHERE one = 'six' LIMIT 1");
         $this->assertNotFalse($result);
         
-        
         $field = mysql_fetch_field($result, 2);
         $this->assertFalse($field);
     }
@@ -1349,8 +1491,8 @@ class MySqlShimTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
                 six varchar(255),
                 seven varchar(255),
                 eight varchar(255),
-                nine ENUM('one', 'two', '\'three', 'three', 'four', 'five', 'six'),
-                ten SET('one', 'two', '\'\'three', 'three', 'four', 'five', 'six'),
+                nine ENUM('one', 'two', '\'three', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'),
+                ten SET('one', 'two', '\'\'three', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'),
                 eleven MEDIUMTEXT,
                 INDEX one_idx (one),
                 UNIQUE INDEX two_unq (two),