RSS template has incorrect value for lastBuildDate

[tastapod]

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

$ hugo version
hugo v0.119.0-b84644c008e0dc2c4b67bd69cccf87a41a03937e+extended darwin/arm64 BuildDate=2023-09-24T15:20:17Z VendorInfo=brew

Does this issue reproduce with the latest release?

Yes

Steps to reproduce

1. Build site with hugo command
2. Check the top-level /index.xml file

Description

In Hugo 0.119, the internal RSS template has a <lastBuildDate> field based on .Date, which is the date in the site's top-level _index.md file (or the _index.md file for the section or category for sub-feeds, I presume).

Instead it should either be the date the RSS file was built or the date of the most recent published post, so RSS readers can tell whether anything has changed.

I am doing the latter in the following fragment, in a custom /layouts/rss.xml template based on the internal one:

{{- $lastBuildDate := (index $pages.ByDate.Reverse 1).Date -}}
...
<lastBuildDate>{{ $lastBuildDate.Format "Mon, 02 Jan 2006 15:04:05 -0700" | safeHTML }}</lastBuildDate>{{ end }}

I am happy to submit a PR with this change. I can't see it breaking anything except for the case where $pages is empty.

Using the current build time is even easier:

<lastBuildDate>{{ now.Format "Mon, 02 Jan 2006 15:04:05 -0700" | safeHTML }}</lastBuildDate>{{ end }}

I prefer the most recent post date; it feels more RSS-like. The main thing is that the current /index.xml bases the date on /_index.md, which in my case is August 2013!

[jmooring]

Yes, we should change this, but use .Lastmod instead of .Date and remember that array/slice indexes are zero-based:

<lastBuildDate>{{ (index $pages.ByLastmod.Reverse 0).Lastmod.Format "Mon, 02 Jan 2006 15:04:05 -0700" | safeHTML }}</lastBuildDate>

Please submit PR.

[tastapod]

Ah thanks, I misread the collections.Index docs. Will do.

[tastapod]

I found another RSS template, which is for the Hugo docs site. This has the same bug.

I propose factoring out the expression in line 20 so the first line of the template is:

{{- $pages := first 50 (where .Site.RegularPages "Type" "in" (slice "news" "showcase")) -}}

then use the same (index $pages.ByLastmod.Reverse 0).Lastmod expression for the lastModDate field.

WDYT?

[jmooring]

I think you should focus on the original issue, and raise a separate issue in the docs repository.

[tastapod]

Ok will do.

I'm getting test failures on a fresh checkout. I've asked for help but nothing yet. I'm pretty sure this change won't make things any worse, but I have an allergic reaction to checking in code with broken tests!

[github-actions]

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