Version 4.34.0 introduced bug parsing slots in VUE 2.x which breaks storybook docs.

[piscis]

Current behavior

After upgrading our lock file we received lot of warnings while running storybook build.

Currently we're using Storybook 6.1.6 + VUE.JS (2.x).

Console output

Module Warning (from /home/runner/work/fooproject/node_modules/vue-docgen-loader/lib/index.js):
[vue-docgen-loader] failed to parse the component file with docgen-api: Cannot read property 'leadingComments' of null

 @ ./src/stories/frontend/forms/FormDummyLogin.stories.js 66:0-76 70:13-27 91:17-31
 @ ./src sync ^\.(?:(?:^|\/|(?:(?:(?!(?:^|\/)\.).)*?)\/)(?!\.)(?=.)[^/]*?\.stories\.(js|jsx|ts|tsx|mdx))$
 @ ./config/storybook/generated-stories-entry.js
 @ multi /home/runner/work/fooproject/node_modules/@storybook/core/dist/server/common/polyfills.js /home/runner/work/fooproject/node_modules/@storybook/core/dist/server/preview/globals.js ./config/storybook/storybook-init-framework-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-docs/dist/frameworks/common/config.js-generated-other-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-docs/dist/frameworks/vue/config.js-generated-other-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-links/dist/preset/addDecorator.js-generated-other-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-actions/dist/preset/addDecorator.js-generated-other-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-actions/dist/preset/addArgs.js-generated-other-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-backgrounds/dist/preset/addDecorator.js-generated-other-entry.js /home/runner/work/fooproject/node_modules/@storybook/addon-backgrounds/dist/preset/addParameter.js-generated-other-entry.js ./config/storybook/preview.js-generated-config-entry.js ./config/storybook/generated-stories-entry.js

Current dependency from storybook in yarn.lock

....
"@storybook/vue@6.1.6":
  version "6.1.6"
  dependencies:
    "@storybook/addons" "6.1.6"
    "@storybook/core" "6.1.6"
    "@types/webpack-env" "^1.15.3"
    core-js "^3.0.1"
    global "^4.3.2"
    react "16.13.1"
    react-dom "16.13.1"
    regenerator-runtime "^0.13.7"
    ts-dedent "^2.0.0"
    ts-loader "^6.2.2"
    vue-docgen-api "^4.33.1"
    vue-docgen-loader "^1.5.0"
    webpack "^4.44.2"
....

One side effect is that you're storybook is building with the errors and that a storybook:build is missing our stylesheets. The Docs Tab is also broken and the props and event tabs under control are missing.

To reproduce

Sorry I don't have a demo repo, I can show right now but I tracked the error down. Since we're updateing the lock on a daily base I realized that 4.34.0 contains a fix for slots

https://github.com/vue-styleguidist/vue-styleguidist/releases/tag/v4.34.0

If I pin vue-docgen-api to 4.33.9 via resolutions in our yarn file it stops emitting this warning.

Expected behavior

It should build without warnings and show props and events in Doc Tabs and controls.

Workaround for now

Pin vue-docgen-api to 4.33.9 via yarn resolutions.

...
"resolutions": {
    "**/vue-docgen-api": "4.33.9"
  }
...

[elevatebart]

Alright, I am on it. Sry for the inconvenience.