[hakyll] Easy way to add an updated date field

[Deepak Jois]

Hi

In addition to the ‘published’ date, I want to track an ‘updated’
field in my YAML frontmatter which denotes the date a post was
updated.

After looking around, the best I could come up with was this:
https://github.com/deepakjois/website/commit/2d23f9d47e927f58fd450a327e6907ef1b0b2b64

It is essentially code lifted from the core Hakyll codebase with
function names and a string value (published -> updated) changed.

Is there a better way to do this? Can the Hakyll API provide a way to
specify additional date fields in the YAML front matter easily?

Thanks
Deepak

[Gwern Branwen]

Post by Deepak Jois
Is there a better way to do this? Can the Hakyll API provide a way to
specify additional date fields in the YAML front matter easily?

Isn't this already covered by 'modificationTimeField'?

[Deepak Jois]

Post by Gwern Branwen

Post by Deepak Jois
Is there a better way to do this? Can the Hakyll API provide a way to
specify additional date fields in the YAML front matter easily?

Isn't this already covered by 'modificationTimeField'?

Not really. modificationTimeField seems to work with modification
times of files on a filesystem. This may not work, say if I clone my
site’s git repo on another machine. I will lose the info of when the
post was last updated.

What I am looking for is to explicitly track a date value (under a key
like ‘updated’ or ‘lastupdated’ or whatever) in the post metadata,
which I can then format and display.

Deepak

[Gwern Branwen]

Post by Deepak Jois
What I am looking for is to explicitly track a date value (under a key
like ‘updated’ or ‘lastupdated’ or whatever) in the post metadata,
which I can then format and display.

I see. In that case, maybe you could do something with filestore? I assume
you version-control your site, so you could use filestore to extract the
date of the last patch modifying each particular file and store that as a
variable and then transclude it.

Another method might be editor-based. It would be maddeningly tedious to
update afield yourself but it is possible to script an editor to
automatically update a particular line in a file. For example, in Emacs:
https://www.gnu.org/software/emacs/manual/html_node/emacs/Time-Stamps.html#Time-Stamps
The default format there might not be YAML compatible but you can probably
come up with one which is.

[Jasper Van der Jeugt]

It depends on what you want to do. If you only want to format and
display this value, it's easy:

1. Add an "updated: 2017-03-14" field to all your posts.
2. Add a field to your context which parses and formats this value:

field "updated" (\item -> do
mbUpdated <- getMetadataField (itemIdentifier item) "updated"
maybe empty return $ do
updated <- mbUpdated
time <- parseTime defaultTimeLocale "%Y-%m-%d" updated
:: Maybe UTCTime
return $ formatTime defaultTimeLocale "%B %e, %Y" time)

3. Use the `$updated$` key in your templates.

Hope this helps,
Jasper

Post by Gwern Branwen

Post by Deepak Jois
What I am looking for is to explicitly track a date value (under a key
like ‘updated’ or ‘lastupdated’ or whatever) in the post metadata,
which I can then format and display.

I see. In that case, maybe you could do something with filestore? I assume
you version-control your site, so you could use filestore to extract the
date of the last patch modifying each particular file and store that as a
variable and then transclude it.
Another method might be editor-based. It would be maddeningly tedious to
update afield yourself but it is possible to script an editor to
https://www.gnu.org/software/emacs/manual/html_node/emacs/Time-Stamps.html#Time-Stamps
The default format there might not be YAML compatible but you can probably
come up with one which is.
--
gwern
https://www.gwern.net
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