SplFileObject::isReadable and SplFileObject::isWriteable provide an untrustworthy interface

Description

isReadable and isWriteable only consider the file system permissions but that isn't actually reflective of the state of the object because read and write methods also consider the resource mode so if you trust them you can can run into unexpected bugs as demonstrated in the example below.

Specifically
1 . Streams don't look readable?
2. Resources that are opened write only look readable.

The following code:

<?php

function showFile(\SplFileObject $file) {
    var_dump($file->isReadable());
    if ($file->isReadable()) {
      var_dump($file->fread($file->getSize()));
    }
    echo str_repeat('=', 80) . PHP_EOL;
}

showFile(new SplFileObject(__FILE__));
$f = new SplFileObject('php://temp', 'r+');
$f->fwrite('content');
showFile($f);
showFile(new SplFileObject(__FILE__, 'a'));

Resulted in this output:

bool(true)
string(376) "<?php

function showFile(\SplFileObject $file) {
    var_dump($file->isReadable());
    if ($file->isReadable()) {
      var_dump($file->fread($file->getSize()));
    }
    echo str_repeat('=', 80) . PHP_EOL;
}

showFile(new SplFileObject(__FILE__));
$f = new SplFileObject('php://temp', 'r+');
$f->fwrite('content');
showFile($f);
showFile(new SplFileObject(__FILE__, 'a'));
"
================================================================================
bool(false)
================================================================================
bool(true)
PHP Notice:  SplFileObject::fread(): Read of 8192 bytes failed with errno=9 Bad file descriptor in /tmp/tmp.php on line 6
bool(false)
================================================================================

But I expected this output instead:

bool(true)
string(376) "<?php

function showFile(\SplFileObject $file) {
    var_dump($file->isReadable());
    if ($file->isReadable()) {
      var_dump($file->fread($file->getSize()));
    }
    echo str_repeat('=', 80) . PHP_EOL;
}

showFile(new SplFileObject(__FILE__));
$f = new SplFileObject('php://temp', 'r+');
$f->fwrite('content');
showFile($f);
showFile(new SplFileObject(__FILE__, 'a'));
"
================================================================================
bool(true)
string(7) "content"
================================================================================
bool(false)

PHP Version

all

Operating System

No response

入口点是 SplFileObject::isReadable()、SplFileObject::isWriteable() 以及示例中演示的读写方法。首先跟踪这些方法如何评估文件系统权限与资源模式。为 r+、只写和追加情况添加回归测试覆盖，然后验证报告的输出和预期输出。