feat(generator): export:route hook and setPayload

[pi0]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

This PR allows providing a shared payload to all nuxt export routes similar to generate payload

Thanks for @nilsnh (#6159 (comment)) for discovering this :)

Usage:

nuxt.config

export default {
  target: 'static',
  hooks: {
    export: {
      async before ({ setPayload }) {
        const categories = await backend.getCategories()
        setPayload({ categories })
      }
    }
  }
}

pages/index.vue

export default {
  async asyncData({ params, error, payload }) {
    if (payload) { return { categories: payload.categories } }
    return { categories: await backend.getCategories() }
  }
}

It is also possible for modules using export:route to fill payload per route.

Why using setPayload and not directly allow setting payload props?

Current usage is checking payload is not null (default value) docs. So it changes null to object on first set.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[clarkdo]

Would getter/setter for payload make more sense here ?

[pi0]

We may need something like a proxy then for deep watch. setPayload can ensure it is deep assigned and is simple :)

[clarkdo]

This make me a little confused, we have this.setPayload which is never called.

We also have another setPayload as a scoped var

[pi0]

The one set in the constructor is used by export:before hook to set shared payload.

The one in scoped var is used for export:route hook.

[clarkdo]

Ah, I didn’t realize it’s passed by this.

[clarkdo]

I think I might have understood what’s happening here, so we have a global payload, each route has a scoped payload, what we’re doing is to make sure default value is always populated to updated payload.

[codecov-commenter]

Codecov Report

Merging #7422 into dev will increase coverage by 0.05%.
The diff coverage is 84.21%.

@@            Coverage Diff             @@
##              dev    #7422      +/-   ##
==========================================
+ Coverage   70.20%   70.26%   +0.05%     
==========================================
  Files          88       88              
  Lines        3679     3696      +17     
  Branches     1007     1008       +1     
==========================================
+ Hits         2583     2597      +14     
- Misses        889      892       +3     
  Partials      207      207              

Flag	Coverage Δ
#unittests	70.26% <84.21%> (+0.05%)	⬆️

Impacted Files	Coverage Δ
packages/generator/src/generator.js	86.29% <84.21%> (-0.38%)	⬇️

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