No proper return from partials with 0 as arg

[malcom]

Passing 0 integer as an argument to partial template func with return statement (as a function substitute) prevents this "function" from returning the correct value. It looks like the 0 as partial argument is treated as nil context.

Template:

add42: 50: {{ partial "add42.tpl" 8 }}
add42: 42: {{ partial "add42.tpl" 0 }}

Output:

add42: 50: 50
add42: 42: 

File partials/add42.tpl

{{ $v := add . 42 }}
{{ return $v }}

This issue is reproducable with the latest release.

[igorburago]

I just ran into this problem (in version 0.74.3), as well. In fact, the
bug manifests itself not only when the passed context argument
is zero, but also when it is any empty value: nil; false; string, slice,
or dictionary of zero length. Hugo shows no warnings or errors
pertaining such partial call.

A minimal failing test is as follows:

X{{ partial "retval" dict }}X
{{ define "partials/retval" }}
  {{ return 123 }}
{{ end }}

It incorrectly renders to XX instead of the expected X123X.

The same thing happens when dict is replaced with slice, "",
false, 0, or nil via, say, $.Site.Params.nonexistentparameter.
The erroneous behavior does not depend on the body of the partial
nor the value given in the return statement, as long as the latter is
present in the partial.

A practical example of when this behavior is problematic is the
following partial returning a slice of key-value records from the
dictionary given in the context argument. When the dictionary is
empty, due to the bug, it returns nil instead of the empty slice.

{{ define "partials/itemize" }}
  {{- $items := slice -}}
  {{- range $i, $x := . -}}
    {{- $items = $items | append (dict "index" $i "item" $x) -}}
  {{- end -}}
  {{- return $items -}}
{{ end }}

[github-actions]

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