[Proposal] Use 'Scratch Pad' instead of now.UnixNano

[TetraTheta]

Using now.UnixNano will change <a>'s ID every time the site is built.

In most cases, this is fine. But in my case, it didn't work well. When testing my site locally, a few bs/collapse shared the same ID. This made them to be opened or closed at once, together. I don't know why that happened, because that means multiple bs/collapse were generated at the same time, and the chance is highly unlikely.

So I changed the $id part to be like this:

{{- $id := printf "collapse-%s" (delimit (shuffle (seq 1 9)) "") -}}

This also works for creating distinct IDs.

Both now.UnixNano and delimit (shuffle (seq 1 9)) "" have a problem. They will create a different ID every time they are called. If you build a site twice without changing anything, the build results won't be the same because of the different IDs.

After a brief search, I've found that Hugo supports a per-page scratch pad. Since the scratch pad is only shared on a single page, we can safely use incremental numbers for the IDs because no same number will occur on a single page if we increment it properly.

I tested this for my site, and it works as intended. It even worked for nested bs/collapse. The only difference is that I use %03d instead of %d for numbers.

This might increase build time because now Hugo has to assign a map for each page, instead of just getting now.UnixNano.

[razonyang]

Thanks.