Vague error when /storage/runtime/temp isn't writable

[Wiejeben]

Description

For some reason I was unable to upload files on my live server. When trying this, I was given a simple JavaScript alert saying "There was a problem with uploading the file.". After some digging and commenting out code, I discovered that this was because /storage/runtime/temp was not writable.

A possible fix would be to improve \craft\controllers\AssetsController::_getUploadedFileTempPath. Right now throw new UploadFailedException(0); is thrown when \craft\web\UploadedFile::saveAsTempFile throws an exception. Having the exception message of \yii\base\ErrorException shown in the JavaScript alert (or web.log) would have made it less confusing to me.

Steps to reproduce

1. Make sure /storage/runtime/temp is not writable.
2. Attempt to upload a file

Additional info

• Craft version: 3.0.4
• PHP version: 7.0.27
• Database driver & version: MySQL 5.7.21
• Plugins & versions: -

Note: I am using Docker, which is why file permissions are a bit more complicated.

[brandonkelly]

We wouldn’t want to expose the original PHP error, because it will likely contain a file path, which is considered sensitive. However I’ve just updated the exception handling so that it will at least log the original error. So if this crops up again, you can search your logs for “An error occurred when saving an asset”, and you fill find the full exception logged right after that (including the original error).