fix(vue-app): preview mode fetch

[mdoesburg]

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

Changes:

1. Make sure all fetch hooks get called properly in preview mode

Prior to this change, if a page component contained a fetch hook, all underlying component fetch hooks would not be called in preview mode. In addition to that, if a component contained a fetch hook and sub components of the component also contained a fetch hook, only the root component fetch hook would be called in preview mode.

2. Make sure that potential asyncData and old fetch hooks resolve prior to any new fetch hook calls in preview mode in accordance with the Nuxt lifecycle diagram

Prior to this change, if you dynamically rendered components based on data from the asyncData hook, and the dynamically rendered components contained a fetch hook, those fetch hooks would not be called, because asyncData, old fetch, and new fetch were all resolving in parallel in preview mode.

Resolves:

• enablePreview does not call all fetch hooks #10483
• enablePreview not triggering component fetch #8172

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.

[Atinux]

Looks good to me, will need a second eye on this from @danielroe

[danielroe]

This looks good to me - nice changes.

The one question I have is about the comment on https://github.com/nuxt/nuxt.js/blob/0742f59e2478bd3998fd4d49b6200584ee5e2721/packages/vue-app/template/utils.js#L61 but if you're happy with this @Atinux then I am too.

[Atinux]

I think it's fine to reload the templates when we do a full refresh on preview mode. @pi0 do you want to take a look at it or happy to merge and let people use it with nuxt-edge?

[pi0]

Generally looks good to me. We are introducing a behavior change that but it makes lifecycle more explicit can only slightly affect performance in cases usage was depending on the parallel run.

[pi0]

Looks good to me. Pending for #10510 before merging new PRs.

[codecov-commenter]

Codecov Report

Merging #10489 (30014fb) into dev (a10e5dd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev   #10489   +/-   ##
=======================================
  Coverage   65.15%   65.15%           
=======================================
  Files          94       94           
  Lines        4155     4155           
  Branches     1172     1172           
=======================================
  Hits         2707     2707           
  Misses       1169     1169           
  Partials      279      279           

Flag	Coverage Δ
unittests	65.15% <ø> (ø)

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[pi0]

LGTM