Error: unable to cast <nil> since hugo v0.87

[AndreasAZiegler]

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

$ hugo version
hugo v0.87.0+extended linux/amd64 BuildDate=unknown

Does this issue reproduce with the latest release?

Yes

Since hugo v0.87.0 we get the error

Error: Error building site: failed to render pages: render of "section" failed: "/data/repos/hugo-web-ch/layouts/events/list.html:51:44": execute of template failed: template: events/list.html:51:44: executing "main" at <time .Params.date_end "Local">: error calling time: unable to cast <nil> of type
<nil> to Time

for this part of the code

{{/* Render only events which: */}}
{{/* - end date is given (= not unset, "ne" "nil"), and this end date */}}
{{/*   is later than the limit; */}}
{{/* - OR end date is not given (= is unset, "eq" "nil"), and then */}}
{{/*   the start date is later than the limit. */}}
{{/* Other events, even if published, are considered as over, and */}}
{{/* will not be displayed in the list anymore. */}}
{{ if or
   (and (ne .Params.date_end nil) (ge (time .Params.date_end "Local") $limit_date))
   (and (eq .Params.date_end nil) (ge .Params.date $limit_date))
}}

[braderhart]

Not sure if this is a bug or not, but first you should just be able to do something like:

{{if or
	(and .Params.date_end (ge (time .Params.date_end "Local") $limit_date))
	(and (not .Params.date_end) (ge .Params.date $limit_date))
}}

Second, if you'd like to cleanup your code a bit you can include all your comments into a single comment:

{{/*	Render only events which:
	- end date is given (= not unset, "ne" "nil"), and this end date is later than the limit;
	- OR end date is not given (= is unset, "eq" "nil"), and then the start date is later than the limit.

	Other events, even if published, are considered as over, and will not be displayed in the list anymore.
*/}}

[AndreasAZiegler]

@braderhart Thanks for your input.

I adjusted the code to

      {{/* Define a datetime limit to be the present day at 0:00. */}}
      {{ $limit_date := time (substr (now.AddDate 0 0 0) 0 10) "Local" }}
      {{ range sort .Pages ".Params.date" "asc" }}

      {{/* Render only events which: */}}
           - end date is given, and this end date is later than the limit;
           - OR end date is not given, and then the start date is later than the limit.

           Other events, even if published, are considered as over, and will not be displayed in the list anymore.
      */}}
      {{ if or
        (and .Params.date_end (ge (time .Params.date_end "Local") $limit_date))
        (and (not .Params.date_end) (ge .Params.date $limit_date))
      }}

but I still get the error

Error: Error building site: failed to render pages: render of "section" failed: "/data/repos/hugo-web-ch/layouts/events/list.html:50:35": execute of template failed: template: events/list.html:50:35: executing "main" at <time .Params.date_end "Local">: error calling time: unable to cast <nil> of type
<nil> to Time

[bep]

I'm not sure how the above could have changed in the latest release, but we should handle nil inputs, so I will fix that.

That said, the reason @braderhart 's suggestion does not work is that and/or in Go templates does not short circuit (this will be fixed in Go 1.17).

[bep]

I have reverted the above "fix" after thinking about it:

• nil is not a valid date/time
• The reason your code now fails is that we fixed the error handling in time function, so you now get an error and not just a string describing the error.

[AndreasAZiegler]

Then how can I adjust the code to avoid nil?

[jmooring]

@AndreasAZiegler Please show an example of event frontmatter.

[AndreasAZiegler]

Below an example of date and date_end:

date: 2021-08-25T18:00:47+0200
date_end: 2021-08-25T21:00:00+0200

[jmooring]

@AndreasAZiegler

There may be a more concise way to do this...

{{ range .Pages }}

  {{ $render := false }}

  {{ with .Params.date_end }}
    {{ if (time .).After $limit_date }}
      {{ $render = true }}
    {{ end }}
  {{ else }}
    {{ if .Date.After $limit_date }}
      {{ $render = true }}
    {{ end }}
  {{ end }}

  {{ if $render }}
    <h2><a href="{{ .RelPermalink }}">{{ .Title }}</a></h2>
  {{ end }}

{{ end }}

[jmooring]

More concise...

{{ range $p := .Pages }}
  {{ with or .Params.date_end .Date }}
    {{ if (time .).After $limit_date }}
      <h2><a href="{{ $p.RelPermalink }}">{{ $p.Title }}</a></h2>
    {{ end }}
  {{ end }}
{{ end }}