Cannot install any plugin if sample repo doesn't have extensions.json file

[svor]

Describe the bug

After creating a workspace via factory with the project sample which doesn't contain .vscode/extensions.json, I tried to use the Plugins view to install some plugins. As a result plugins were marked as installed, but not into tools container, because /plugins folder doesn't exist in tools container. See screenshots.

Repo url: https://github.com/crw-samples/web-nodejs-sample/tree/che-qe-no-extensions

Devfile.yaml

schemaVersion: 2.1.0
metadata:
  name: nodejs-web-app
components:
  - name: tools
    container:
      image: quay.io/devspaces/udi-rhel8:3.1
      endpoints:
        - exposure: public
          name: nodejs
          protocol: http
          targetPort: 3000
      memoryLimit: 1G
      mountSources: true
      volumeMounts:
        - name: npm
          path: /home/user/.npm
  - name: npm
    volume:
      size: 1G
commands:
  - id: 1-dependencies
    exec:
      label: "Download dependencies"
      component: tools
      workingDir: ${PROJECTS_ROOT}/web-nodejs-sample/app
      commandLine: "npm install"
      group:
        kind: build
  - id: 2-run
    exec:
      label: "Run the web app"
      component: tools
      workingDir: ${PROJECTS_ROOT}/web-nodejs-sample/app
      commandLine: "nodemon app.js"
      group:
        kind: run
  - id: 3-install-and-run
    exec:
      label: "Run the web app (and download dependencies)"
      component: tools
      workingDir: ${PROJECTS_ROOT}/web-nodejs-sample/app
      commandLine: "npm install; nodemon app.js"
      group:
        kind: run
  - id: 4-debug
    exec:
      label: "Run the web app (debugging enabled)"
      component: tools
      workingDir: ${PROJECTS_ROOT}/web-nodejs-sample/app
      commandLine: "nodemon --inspect app.js"
      group:
        kind: debug
        isDefault: true
  - id: 5-stopapp
    exec:
      label: "Stop the web app"
      component: tools
      commandLine: >-
          node_server_pids=$(pgrep -fx '.*nodemon (--inspect )?app.js' | tr "\\n" " ") &&
          echo "Stopping node server with PIDs: ${node_server_pids}" && 
          kill -15 ${node_server_pids} &>/dev/null && echo 'Done.'
      group:
        kind: run

Che version

next (development version)

Steps to reproduce

1. start the workspace by factory: https://che-host/#/https://github.com/crw-samples/web-nodejs-sample/tree/che-qe-no-extensions
2. Open plugins view and install Go plugin
3. Check /plugins folder in tools container

Expected behavior

Plugins should be installed into the tools container

Runtime

OpenShift

Screenshots

Installation method

chectl/next

Environment

Linux

Eclipse Che Logs

No response

Additional context

No response

[vitaliy-guliy]

It seems the support of remote plugins, that are running in the remote UDI container is broken.

I was able to install markdown-mermaid plugin (screenshot 1). che-theia-plugin.yaml of this plugin does not describe a sidecar, so che-theia downloads the plugin extensions into theia-ide container.
If the sidecar is specified, che-theia will download the extension into /plugins/sidecars/tools/ directory.

This directory must be bind with /plugins directory in tools container. But this directory is missing and necessary THEIA_* environment variables are not set (screenshot 2).
That is a reason why such kind of plugins are not working.