[Bug]: Weird state in appdata, incorrect return type handling

[kesselb]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Likely related to: #38761

After running tests locally, I end up with a wiped appdata from time to time.

Visiting the app store greets me with a friendly:

{
  "reqId": "YvlS81wDtRf9uV5nQ1v5",
  "level": 3,
  "time": "2023-11-21T16:27:23+00:00",
  "remoteAddr": "172.19.0.1",
  "user": "admin",
  "app": "index",
  "method": "GET",
  "url": "/index.php/settings/apps",
  "message": "Exception thrown: OCP\\Files\\GenericFileException",
  "userAgent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36",
  "version": "28.0.0.6",
  "exception": {
    "Exception": "OCP\\Files\\GenericFileException",
    "Message": "",
    "Code": 0,
    "Trace": [
      {
        "file": "/var/www/html/lib/private/Files/SimpleFS/SimpleFile.php",
        "line": 74,
        "function": "getContent",
        "class": "OC\\Files\\Node\\File",
        "type": "->",
        "args": []
      },
      {
        "file": "/var/www/html/lib/private/App/AppStore/Fetcher/Fetcher.php",
        "line": 166,
        "function": "getContent",
        "class": "OC\\Files\\SimpleFS\\SimpleFile",
        "type": "->",
        "args": []
      },
      {
        "file": "/var/www/html/lib/private/App/AppStore/Fetcher/AppFetcher.php",
        "line": 187,
        "function": "get",
        "class": "OC\\App\\AppStore\\Fetcher\\Fetcher",
        "type": "->",
        "args": [
          false
        ]
      },
      {
        "file": "/var/www/html/lib/private/Installer.php",
        "line": 423,
        "function": "get",
        "class": "OC\\App\\AppStore\\Fetcher\\AppFetcher",
        "type": "->",
        "args": [
          false
        ]
      },
      {
        "file": "/var/www/html/apps/settings/lib/Controller/AppSettingsController.php",
        "line": 154,
        "function": "isUpdateAvailable",
        "class": "OC\\Installer",
        "type": "->",
        "args": [
          "files_versions"
        ]
      },
      {
        "file": "/var/www/html/apps/settings/lib/Controller/AppSettingsController.php",
        "line": 137,
        "function": "getAppsWithUpdates",
        "class": "OCA\\Settings\\Controller\\AppSettingsController",
        "type": "->",
        "args": []
      },
      {
        "file": "/var/www/html/lib/private/AppFramework/Http/Dispatcher.php",
        "line": 230,
        "function": "viewApps",
        "class": "OCA\\Settings\\Controller\\AppSettingsController",
        "type": "->",
        "args": []
      },
      {
        "file": "/var/www/html/lib/private/AppFramework/Http/Dispatcher.php",
        "line": 137,
        "function": "executeController",
        "class": "OC\\AppFramework\\Http\\Dispatcher",
        "type": "->",
        "args": [
          [
            "OCA\\Settings\\Controller\\AppSettingsController"
          ],
          "viewApps"
        ]
      },
      {
        "file": "/var/www/html/lib/private/AppFramework/App.php",
        "line": 184,
        "function": "dispatch",
        "class": "OC\\AppFramework\\Http\\Dispatcher",
        "type": "->",
        "args": [
          [
            "OCA\\Settings\\Controller\\AppSettingsController"
          ],
          "viewApps"
        ]
      },
      {
        "file": "/var/www/html/lib/private/Route/Router.php",
        "line": 315,
        "function": "main",
        "class": "OC\\AppFramework\\App",
        "type": "::",
        "args": [
          "OCA\\Settings\\Controller\\AppSettingsController",
          "viewApps",
          [
            "OC\\AppFramework\\DependencyInjection\\DIContainer"
          ],
          [
            "",
            "",
            "settings.AppSettings.viewApps"
          ]
        ]
      },
      {
        "file": "/var/www/html/lib/base.php",
        "line": 1069,
        "function": "match",
        "class": "OC\\Route\\Router",
        "type": "->",
        "args": [
          "/settings/apps"
        ]
      },
      {
        "file": "/var/www/html/index.php",
        "line": 37,
        "function": "handleRequest",
        "class": "OC",
        "type": "::",
        "args": []
      }
    ],
    "File": "/var/www/html/lib/private/Files/Node/File.php",
    "Line": 56,
    "message": "",
    "exception": {},
    "CustomMessage": "Exception thrown: OCP\\Files\\GenericFileException"
  }
}

Steps to reproduce

1. Clear appdata
2. Internal server error
3. 😞

Expected behavior

I assume it's okay that your instance is bricked if you deleted app data.

However, there are also some weird paths in our code.

server/lib/private/App/AppStore/Fetcher/Fetcher.php

Lines 183 to 186 in d14d881

	} catch (NotFoundException $e) {
	// File does not already exists
	$file = $rootFolder->newFile($this->fileName);
	}

Above code should handle that situation, a local copy of apps.json does not exist, properly.
It does not because a OCP\Files\GenericFileException is thrown instead of the expected OCP\Files\NotFoundException.

server/lib/private/Files/SimpleFS/SimpleFile.php

Lines 80 to 95 in 8b59974

	/**
	* Get the content
	*
	* @throws NotPermittedException
	* @throws NotFoundException
	* @return string
	*/
	public function getContent() {
	$result = $this->file->getContent();
	if ($result === false) {
	$this->checkFile();
	}
	return $result;
	}

ISimpleFile.getContent does a check for false.
After #37943 the method does not return false but throws a OCP\Files\GenericFileException.

Installation method

None

Nextcloud Server version

master

Operating system

Debian/Ubuntu

PHP engine version

Other

Web server

Apache (supported)

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[kesselb]

Index: lib/private/Files/SimpleFS/SimpleFile.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/lib/private/Files/SimpleFS/SimpleFile.php b/lib/private/Files/SimpleFS/SimpleFile.php
--- a/lib/private/Files/SimpleFS/SimpleFile.php	(revision 0da05fc73b720702b76d8838228f3ce648793482)
+++ b/lib/private/Files/SimpleFS/SimpleFile.php	(date 1700585207323)
@@ -25,6 +25,7 @@
 namespace OC\Files\SimpleFS;
 
 use OCP\Files\File;
+use OCP\Files\GenericFileException;
 use OCP\Files\NotFoundException;
 use OCP\Files\NotPermittedException;
 use OCP\Files\SimpleFS\ISimpleFile;
@@ -71,9 +72,9 @@
 	 * @throws NotFoundException
 	 */
 	public function getContent(): string {
-		$result = $this->file->getContent();
-
-		if ($result === false) {
+		try {
+			$result = $this->file->getContent();
+		} catch (GenericFileException) {
 			$this->checkFile();
 		}

Make the internal error go away and recreate the appstore folder and files inside.
I'm however not sure if that's inline with the behavior implemented in #8289 back then.

[nickvergessen]

Also that might be okay for the appstore files, but definitely not all other data. If a user encryption key can not be read etc recreating is not an option.