"len of untyped nil" on list I can successfully range over

support
1

I’m writing a new theme from scratch. I have a single index.html and a single partial. This is index.html in its entirety:

 {{ $paginate := .Paginate (where .Site.Pages "Type" "post") }}
  {{ range $paginate.Pages }}
    {{ partial "detail.html" . }}
  {{ end }}

And this is the detail.html partial:

 <div class="tags">
        {{ $total := len .Params.tags }}
        {{ range $i, $tag := .Params.tags }} // this works if I remove the line above
        <a href="{{ "/tags/" | relURL }}{{ $tag |urlize}}">{{ $tag }}&nbsp;</a>
        {{ end }}
  </div>

I’m able to range over .Params.tags without issue, but calling len on .Params.tags throws:

 at <len .Params.tags>: error calling len: len of untyped nil

Content example:

---
title: "Test"
date: 2018-07-18:37:59-07:00
tags: ["test"]
draft: false
---

WTF

hugo env:

 Hugo Static Site Generator v0.42.2 linux/amd64 BuildDate: 2018-07-02T23:39:55+0200
 GOOS="linux"
 GOARCH="amd64"
 GOVERSION="go1.10.3"
1 Like
2

Untested wild guess: does the Param you’re testing for exist on all content? In other contexts “with” helps this.

3

The content is only that single example post, so can confirm it’s not from missing tag frontmatter. However {{ with .Params.tags }} produces a new error:

can't evaluate field Params in type []string

I’m getting the same issue when I try it as toml frontmatter as well:

+++
title = "Test"
date = "2018-07-18:37:59-07:00"
tags = ["test"]
draft = false
+++

For some reason it evaluates properly with range but not with or len

4

Super odd, if I add {{ printf "%#v" .Params.tags}}

I get []string{"test"} so it’s getting populated for sure

Also in the top example I use .Site.Pages which does include a top level “Posts” obj without tags, but using .Data.Pages doesn’t, and produces the same result.

5

Have you figured it out this problem?

6

I did not

7

I know that the original question is from ages ago, but have you tried .Page.Params.tags from within the partial?

This seems like a scoping issue.

8

I have exactly the same issue. I have this code:

{{ $pgs := .Param "componentOf" }}
{{ printf "Variable: %#v\n" $pgs }}

It generates either []string{} or []string{ "..." }, yet:

{{ $pgs := .Param "componentOf" }}
{{ printf "Variable: %#v\n" $pgs }}

{{ $pgsc := len $pgs }}
{{ printf "%+v\n" $pgsc }}

causes:

Rebuild failed:

Failed to render pages: render of "section" failed: "/Users/bsheward/site/themes/genesis/layouts/service/list.html:15:40": execute of template failed: template: service/list.html:15:40: executing "main" at <len $pgs>: error calling len: reflect: call of reflect.Value.Type on zero Value

13 {{ printf "Variable: %#v\n" $pgs }}
14
15 {{ $pgsc := len $pgs }}
16 {{ printf "%+v\n" $pgsc }}

Surely len should return 0 if it is passed an empty string array, right?

9

I encountered the same error. In my case, the tags were not defined for some posts, so it was failing to process those (even though the single file I was testing on had tags aplenty). Testing using ‘with’ first fixed it.