theia: Problems installing hello-world-extension

Hello,

probably a newbie question: I followed the “Authoring an extension” example in the Theia gitbook and ran the yeoman generator. Further, I did the “Build your own IDE” steps in a separate project. Combining the two, as plugging the hello-world-extension into the custom IDE fails for me. I chose electron as target and while the shell does start up, it hangs displaying the busy-indicator.

Custom Theia package.json:

{
  "private": true,
  "dependencies": {
    "typescript": "latest",
    "@theia/typescript": "next",
    "@theia/navigator": "next",
    "@theia/terminal": "next",
    "@theia/outline-view": "next",
    "@theia/preferences": "next",
    "@theia/messages": "next",
    "@theia/git": "next",
    "@theia/file-search": "next",
    "@theia/markers": "next",
    "@theia/preview": "next",
    "@theia/callhierarchy": "next",
    "@theia/merge-conflicts": "next",
    "@theia/search-in-workspace": "next",
    "@theia/json": "next",
    "@theia/textmate-grammars": "next",
    "@theia/mini-browser": "next",
    "@theia/java": "next",
    "@theia/keymaps": "next",
    "hello-world-extension": "../theia-hello-world/hello-world-extension"
  },
  "devDependencies": {
    "@theia/cli": "next"
  },
  "theia" : {
    "target":"electron"
  }
}

yarn yarn theia build Apart from some keybinding collisions no further errors are shown. yarn theia rebuild:electron yarn theia start When I issue the --inspect flag, with custom or default port, the application stops as the given port is already in use (this seems to be a node issue).

[Edit] I also tried to install the extension from a local registry (Verdaccio) with no success.

Am I missing something? Thanks in advance.