Why won't time.Format accept input read from Json data?

support
1

Edit: as explained in my subsequent post, there’s nothing wrong with passing variables to time.Format, provided that variable has a string value.

I’m struggling to get time.Format to accept data read from a json file.

The original data looks like

{ "startDate": "2023-01-28T15:00" }

Which I’ve put in a variable $json_data.startDate

What I’m essentially trying to do is

{{ time.Format "Monday, Jan 2, 2006" "2023-01-28"  }}

Except passing “2023-01-28” as a variable. The snag I’ve hit is

{{ time.Format "Monday, Jan 2, 2006" (substr $json_map.startDate 0 10) }}

causes running hugo to barf:

$ hugo
Start building sites … 
hugo v0.108.0+extended linux/amd64 BuildDate=unknown
ERROR 2023/01/12 08:33:19 render of "page" failed: "/home/roblaing/webapps/joeblog/themes/joetheme/layouts/_default/single.html:8:7": execute of template failed: template: _default/single.html:8:7: executing "main" at <time.Format>: error calling Format: unable to parse date: 
Error: Error building site: failed to render pages: render of "page" failed: "/home/roblaing/webapps/joeblog/themes/joetheme/layouts/_default/single.html:8:7": execute of template failed: template: _default/single.html:8:7: executing "main" at <time.Format>: error calling Format: unable to parse date: 
Total in 40 ms

There’s something clearly wrong with the type of the substring. But

{{ eq (substr $json_map.startDate 0 10) "2023-01-28" }}

is true, so I’m at a loss at how to transform the input.

I found a similar question from a while back at Date in Template from Data (json) but couldn’t figure out the solution from the replies.

2

How did you do this? Seeing more of your code would be helpful.

1 Like
3

I’ve read it from a json file in the data directory using

{{ $json_map := (index (index .Site.Data .Page.Section) (path.Base .RelPermalink)) }}
4

Maybe your data structure isn’t what you think it is.

This works fine:

data/foo.json

{
  "startDate": "2023-01-28T15:00"
}

template

{{ $json_map := site.Data.foo }}
{{ time.Format "Monday, Jan 2, 2006" (substr $json_map.startDate 0 10) }}

output

Saturday, Jan 28, 2023
1 Like
5

It turns out there’s nothing wrong with Hugo’s time.Format, just that I forgot to guard against attempting to read json files which don’t have the “startDate” key.

Adding this guard fixed it:

{{ if isset $json_map "startDate" }}
{{ time.Format "Monday, Jan 2, 2006" (substr $json_map.startDate 0 10) }}
{{ end }}
6

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