[BUGFIX] Disallow deleting extensions in Composer mode

Deleting an extension in Extension Manager doesn't make much sense in a
Composer-based installation. For this reason, the removal of extensions
is prohibited now.

Resolves: #91456
Releases: master, 9.5
Change-Id: Ia96cf2741fd749d9f50540366351c8b576cac96b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64568


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Simon Gilli <typo3@gilbertsoft.org>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>

typo3/sysext/extensionmanager/Classes/Controller/ActionController.php

@@ -15,6 +15,7 @@
 
 namespace TYPO3\CMS\Extensionmanager\Controller;
 
+use TYPO3\CMS\Core\Core\Environment;
 use TYPO3\CMS\Core\Messaging\FlashMessage;
 use TYPO3\CMS\Core\Package\Exception;
 use TYPO3\CMS\Core\Package\Exception\PackageStatesFileNotWritableException;
@@ -138,6 +139,13 @@ class ActionController extends AbstractController
     protected function removeExtensionAction($extension)
     {
         try {
+            if (Environment::isComposerMode()) {
+                throw new ExtensionManagerException(
+                    'The system is set to composer mode. You are not allowed to remove any extension.',
+                    1590314046
+                );
+            }
+
             $this->installUtility->removeExtension($extension);
             $this->addFlashMessage(
                 LocalizationUtility::translate(

typo3/sysext/extensionmanager/Resources/Private/Templates/List/Index.html

@@ -112,7 +112,9 @@
                         <div class="btn-group">
                             <em:processAvailableActions extension="{extension}">
                                 <em:updateScript class="btn btn-default" extensionKey="{extension.key}" />
-                                <em:removeExtension class="btn btn-default" extension="{extension}" />
+                                <f:if condition="!{isComposerMode}">
+                                    <em:removeExtension class="btn btn-default" extension="{extension}" />
+                                </f:if>
                                 <f:link.action action="downloadExtensionZip" controller="Action" arguments="{extension:extension.key}" title="{f:translate(key:'extensionList.downloadzip')}" class="btn btn-default">
                                     <core:icon identifier="actions-system-extension-download" />
                                 </f:link.action>