Regression in TOML LocalDate Format Support

[xM8WVqaG]

What version of Hugo are you using (hugo version)?

• Regression introduced in hugo v0.87.0-B0C541E4 linux/amd64 BuildDate=2021-08-03T10:57:28Z VendorInfo=gohugoio
• Regression exists in hugo v0.99.1-d524067382e60ce2a2248c3133a1b3af206b6ef1 linux/amd64 BuildDate=2022-05-18T11:18:14Z VendorInfo=gohugoio
• Last confirmed release where this pattern works is hugo v0.86.0-41C6C52E linux/amd64 BuildDate=2021-07-21T09:53:14Z VendorInfo=gohugoio

Issue

This is quite a minor issue as there is a solution. Feel free to close this if I've misunderstood and this isn't a valid regression.

In Hugo before v0.87 you could use the .Format method on a toml.LocalDate date. Since then with the new TOML backend and updated .Format functionality it errors.

For hugo <= 0.86, given the toml:

date = 2021-10-19

This template renders correctly:

{{ with index . "date" }}
  <dt class="cite__key">Date</dt>
  <dd class="cite__value">
    <time
        datetime='{{ .Format "2006-01-02" }}'>
      {{ .Format "2006-01-02" }}
    </time>
  </dd>
{{end}}

From hugo >= 0.87 it errors with:

Error: Error building site: failed to render pages: render of "page" failed: "/path/to/hugo/template.html:42:25": execute of template failed: template: hugo/template.html:42:25: executing "main" at <.Format>: can't evaluate field Format in type toml.LocalDate

However, calling time.Format directly and passing in toml.LocalDate as an argument does correctly render.

{{ with index . "date" }}
  <dt class="cite__key">Date</dt>
  <dd class="cite__value">
    <time
        datetime='{{ time.Format "2006-01-02" . }}'>
      {{ time.Format "2006-01-02" . }}
    </time>
  </dd>
{{end}}

Shouldn't toml.LocalDate (which can be coerced into a time.Time) be treated as a just like regular a TOML Offset Date-Time (which I think are automatically time.Time in go-toml).

[bep]

I don't think we can/want to fix this, though.

[jmooring]

When using toml.LocalDate and toml.LocalDateTime values in the four predefined front matter date fields, the values are converted to time.Time, so the .Format method works as expected.

This issue is limited to custom front matter date fields, and date values from local and remote data files.

As noted here, it would be nice if pelletier/go-toml had an option to unmarshal toml.LocalDate and toml.LocalDateTime to time.Time in UTC. Or we walk the tree and do it ourselves.

We've had to make adjustments here and there to accommodate toml.LocalDate and toml.LocalDateTime values:

• https://github.com/gohugoio/hugo/pull/9981
• https://github.com/gohugoio/hugo/pull/11706

It would be nice if we could just handle it while unmarshaling.

---

I've clarified the time.Format documentation here.