fix(nuxt): support deep assign on empty object for app config

[atinux]

🔗 Linked issue

No linked issue, but a reproduction: https://stackblitz.com/edit/github-mgmeto?file=app.config.ts,app.vue

Tested locally in playground with my fix and works.

❓ Type of change

• [ ] 📖 Documentation (updates to the documentation or readme)
• [x] 🐞 Bug fix (a non-breaking change that fixes an issue)
• [ ] 👌 Enhancement (improving an existing functionality like performance)
• [ ] ✨ New feature (a non-breaking change that adds functionality)
• [ ] ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

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[Tahul]

I have a small suggestion about updateAppConfig and the current update strategy.

We currently use deepAssign and deepDelete in sequence so when calling updateAppConfig(content), the content becomes the new appConfig, without mutating the original object reference to preserve reactivity.

The issue with that is that deepDelete will inevitably delete all the missing keys from content, avoiding the possibility to make partial update of the app.config by sending only parts of it.

While this works very good, I think it would be amazing being able to send only partial updates to the app.config, without implying deepDelete.

Also, I don't think deleting keys from the app.config is safe or needed, as if the key is defined it's inevitable that features in the project somehow depend on these keys, and then removing them could lead to runtime throws.

[pi0]

@Tahul Can you please open an issue with steps to reproduce? Indeed update shouldn't delete missing sub-keys too. BTW we initially did it because it was making strange behavior when a user removes an optional-option from main app.config and HMR was not reflecting that.

[atinux]

The deepDelete is only used in development actually for HMR: https://github.com/nuxt/framework/blob/fix/update-app-config/packages/nuxt/src/app/config.ts#L61

What are the steps that brings a bad DX?

[Tahul]

The deepDelete is only used in development actually for HMR: fix/update-app-config/packages/nuxt/src/app/config.ts#L61

What are the steps that brings a bad DX?

Wow, my bad, sorry for not double-checking that.

I thought the same sequence occurred in HMR and in runtime call.

I was mentioning this lately while working on studio because we allow partial updates for tokens.config and I thought that same partial updates would break with app.config. We are going to switch between holding the complete version of the app.config file in json files to holding only the keys that has been modified from studio for performances purpose.

You can consider this closed, sorry 😓