Bug: JSONFormatter->format() cannot handle errordata, only outputs it's own error

[hcbd]

Describe the bug
CI only outputs the error thrown in JSONFormatter->format() function, not the one that preceded it.
CI Outputs:

<br />
<font size='1'><table class='xdebug-error xe-uncaught-exception' dir='ltr' border='1' cellspacing='0' cellpadding='1'>
<tr><th align='left' bgcolor='#f57900' colspan="5"><span style='background-color: #cc0000; color: #fce94f; font-size: x-large;'>( ! )</span> Fatal error: Uncaught CodeIgniter\Format\Exceptions\FormatException: Failed to parse json string, error: "{0}". in /source/system/Format/Exceptions/FormatException.php on line <i>9</i></th></tr>
<tr><th align='left' bgcolor='#f57900' colspan="5"><span style='background-color: #cc0000; color: #fce94f; font-size: x-large;'>( ! )</span> CodeIgniter\Format\Exceptions\FormatException: Failed to parse json string, error: "{0}". in /source/system/Format/Exceptions/FormatException.php on line <i>9</i></th></tr>
<tr><th align='left' bgcolor='#e9b96e' colspan='5'>Call Stack</th></tr>
<tr><th align='center' bgcolor='#eeeeec'>#</th><th align='left' bgcolor='#eeeeec'>Time</th><th align='left' bgcolor='#eeeeec'>Memory</th><th align='left' bgcolor='#eeeeec'>Function</th><th align='left' bgcolor='#eeeeec'>Location</th></tr>
<tr><td bgcolor='#eeeeec' align='center'>1</td><td bgcolor='#eeeeec' align='center'>0.0133</td><td bgcolor='#eeeeec' align='right'>2283712</td><td bgcolor='#eeeeec'>CodeIgniter\Debug\Exceptions->exceptionHandler(  )</td><td title='/source/system/Debug/Exceptions.php' bgcolor='#eeeeec'>.../Exceptions.php<b>:</b>0</td></tr>
<tr><td bgcolor='#eeeeec' align='center'>2</td><td bgcolor='#eeeeec' align='center'>0.0135</td><td bgcolor='#eeeeec' align='right'>2294352</td><td bgcolor='#eeeeec'>CodeIgniter\Debug\Exceptions->respond(  )</td><td title='/source/system/Debug/Exceptions.php' bgcolor='#eeeeec'>.../Exceptions.php<b>:</b>165</td></tr>
<tr><td bgcolor='#eeeeec' align='center'>3</td><td bgcolor='#eeeeec' align='center'>0.0135</td><td bgcolor='#eeeeec' align='right'>2294352</td><td bgcolor='#eeeeec'>CodeIgniter\Debug\Exceptions->format(  )</td><td title='/source/system/API/ResponseTrait.php' bgcolor='#eeeeec'>.../ResponseTrait.php<b>:</b>125</td></tr>
<tr><td bgcolor='#eeeeec' align='center'>4</td><td bgcolor='#eeeeec' align='center'>0.0138</td><td bgcolor='#eeeeec' align='right'>2367056</td><td bgcolor='#eeeeec'>CodeIgniter\Format\JSONFormatter->format(  )</td><td title='/source/system/API/ResponseTrait.php' bgcolor='#eeeeec'>.../ResponseTrait.php<b>:</b>387</td></tr>
</table></font>
{
    "title": "ErrorException",
    "type": "ErrorException",
    "code": 500,
    "message": "Uncaught CodeIgniter\\Format\\Exceptions\\FormatException: Failed to parse json string, error: \"{0}\". in /source/system/Format/Exceptions/FormatException.php:9\nStack trace:\n#0 /source/system/Format/JSONFormatter.php(68): CodeIgniter\\Format\\Exceptions\\FormatException::forInvalidJSON('Type is not sup...')\n#1 /source/system/API/ResponseTrait.php(387): CodeIgniter\\Format\\JSONFormatter->format(Array)\n#2 /source/system/API/ResponseTrait.php(125): CodeIgniter\\Debug\\Exceptions->format(Array)\n#3 /source/system/Debug/Exceptions.php(165): CodeIgniter\\Debug\\Exceptions->respond(Array, 500)\n#4 [internal function]: Code",
    "file": "/source/system/Format/Exceptions/FormatException.php",
    "line": 9,
    "trace": [
        {
            "function": "shutdownHandler",
            "class": "CodeIgniter\\Debug\\Exceptions",
            "type": "->",
            "args": []
        }
    ]
}

CodeIgniter 4 version
4.0.0-rc3

Affected module(s)
Format\JSONFormatter

Expected behavior, and steps to reproduce if appropriate
Get the first error or all errors displayed in the requested format (aka either html, json or xml)

Reproduce
I encountered this bug when i was sending a respons from my controller which uses a model to get information from a database and display that, but i made a typo in my SQL query, which caused an error, which caused another error in JSONFormatter->format().

CodeIgniter4/system/Format/JSONFormatter.php

Line 57 in 2b8c751

public function format($data)

I only found my SQL typo because i added an print_r($data); statement in the above function and saw the 'first' error. This also made me see that the format() function runs twice, once for my error and after that it ran again, this time with the error information of the error generated in the same function
so:

1. first run of format($data)
   it receives an error object via $data,
   json_encode() fails on this object,
   json_last_error() gives 8 (== JSON_ERROR_UNSUPPORTED_TYPE )
   an Exception is thrown because of the json_encode failure,
2. second run of format($data)
   it receives the above thrown error message, which can be parsed by json_encode, so no error
   but now it returns the error array.

The output is like above: a HTML error with after that a JSON error
But the first error is missing completely from this error, which is not handy for debugging

Context

• OS: Fedora 31
• Web server: PHP build-in Webserver
• PHP version 7.3.12

[MGatner]

@hcbd I think I understand what you are saying but if you could supply some clear steps & code to reproduce the error that would help a lot.

[MashinaMashina]

@MGatner
you can use this code:

$JSONFormatter = new JSONFormatter;
$JSONFormatter->format($GLOBALS);

this error because of cirsular references as I understand. In my code error from Postgres has references.

I write

var_dump($data);
exit;

before throw FormatException::forInvalidJSON(json_last_error_msg()); and get this text:
https://pastebin.com/rrR69Sg3 (you can find RECURSION in text)