@storybook/builder-webpack5@6.5.0 breaks the babelModeV7 option

[mmis1000]

Describe the bug
A clear and concise description of what the bug is.

When in condition above, compilation failed with

ERR! TypeError: Cannot read property 'push' of undefined
ERR!     at Object.babel (/<project>/node_modules/@storybook/builder-webpack5/dist/cjs/presets/preview-preset.js:37:18)

To Reproduce

Enable both webpack5 builder and babelModeV7 in 6.5.0

System

Environment Info:

  System:
    OS: Linux 5.4 Ubuntu 20.04.2 LTS (Focal Fossa)
    CPU: (8) x64 AMD Ryzen 9 5950X 16-Core Processor
  Binaries:
    Node: 14.15.0 - ~/.nvm/versions/node/v14.15.0/bin/node
    Yarn: 1.22.10 - ~/.nvm/versions/node/v14.15.0/bin/yarn
    npm: 6.14.8 - ~/.nvm/versions/node/v14.15.0/bin/npm
  Browsers:
    Chrome: 92.0.4515.131
    Firefox: 90.0.2
  npmPackages:
    @storybook/addon-actions: ^6.5.0 => 6.5.0 
    @storybook/addon-essentials: ^6.5.0 => 6.5.0 
    @storybook/addon-links: ^6.5.0 => 6.5.0 
    @storybook/builder-webpack5: ^6.5.0 => 6.5.0 
    @storybook/manager-webpack5: ^6.5.0 => 6.5.0 
    @storybook/vue3: ^6.5.0 => 6.5.0 

Additional context

79e5f5a

This line of code is added in @storybook/builder-webpack5@6.5.0

[mandarini]

Getting a different error, on Nx workspaces with React apps, still webpack5 related. Posted a comment here.

[Tim-arts]

Have the same issue on an Angular SB. In order to make it work I have to set both babelModeV7 and lazyCompilation options to false. My config below:

core: {
    builder: {
      name: 'webpack5',
      options: {
        lazyCompilation: true,
        fsCache: true,
      },
    },
},
features: {
    postcss: false,
    buildStoriesJson: true,
    storyStoreV7: true,
    babelModeV7: true,
},

Note that I'm using the default babel configuration as indicated on this page: https://storybook.js.org/docs/react/configure/babel

[shilman]

Ouch! Sorry gang, should have a fix in the next day or so.

[ntucker]

Is #18279 related to this? I don't have either of those options enabled; but I use custom webpack config so I assume that is equivalent to babelv7 mode?

[shilman]

Gadzooks!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.5.4 containing PR #18284 that references this issue. Upgrade today to the @latest NPM tag to try it out!

npx sb upgrade