How to store version number of a program?

[2-4601]

I use mpv media player on two different computers. Because they have different versions of mpv, I have to make some adjustments and chezmoi is perfect for this job.
For example, in my .chezmoiexternal.toml I have:

{{ $mpv_version := output "sh" "-c" "mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p'" | trim }}
{{/* uosc requires at least mpv version 0.33.0 */}}
{{ if semverCompare ">=0.33.0" $mpv_version }}
[".config/mpv/"]
    type = "archive"
    url = "https://github.com/tomasklaen/uosc/releases/download/{{ (gitHubLatestRelease "tomasklaen/uosc").TagName }}/uosc.zip"
    refreshPeriod = "168h"
{{ end }}

Then in my mpv.conf.tmpl I need the version number again because older versions don't support certain settings:

{{ $mpv_version := output "sh" "-c" "mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p'" | trim }}
{{ if semverCompare ">=0.34.1" $mpv_version }}
watch-later-options-remove=volume
{{ end }}

This setup works, but I'm just wondering if there's a way to store $mpv_version only once when I run chezmoi apply and use its value in different files? Storing it in the chezmoi config file requires running an explicit init command and I would have to remember to do that when mpv is updated to newer versions.

[halostatue]

Each template is run isolated and as far as I can tell has no way of modifying the chezmoi runtime data.

You could consider writing the comparison to a temporary file which then gets deleted using a run_after script.

[bradenhilton]

If you use chezmoi to store the version number somewhere, and read it inside the source state, it will always be behind the source state.

Take the following for example:

1. You use a run_onchange_ template script to detect a new version of mpv and print its version to a file, e.g.:

   # {{ output "sh" "-c" "mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p'" | trim | sha256sum }}
   mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p' > {{ joinPath .chezmoi.homeDir "mpv_version" }}
   

2. You read this file in your templates:

   {{ include (joinPath .chezmoi.homeDir "mpv_version") }}
   

If you set the contents of the mpv_version file to 0 and run chezmoi diff, you will see that it reads 0 in your templates. Only after running chezmoi apply will the mpv_version file be updated.

Not to mention that this violates the assumption that the source and destination states do not change while chezmoi is running.

Do you have any particular concerns with your current implementation? It looks fine to me, you're always reading the version when you need it, and it's always going to be correct.

[2-4601]

Do you have any particular concerns with your current implementation?

No, other than that the call to parse the version number is just very verbose and ugly :) I have to use it in three different files currently. I was just wondering because chezmoi has so many features that there could be a more elegant way to solve what I'm doing.

---

After reading your example I found out about includeTemplate. It seems to solve my issue. For example:

.chezmoitemplates/mpv_version

{{- output "sh" "-c" "mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p'" | trim -}}

mpv.conf.tmpl

{{- $mpv_version := includeTemplate "mpv_version" -}}
{{ if semverCompare ">=0.34.1" $mpv_version }}
watch-later-options-remove=volume
{{ end }}

I'm not sure if this violates "the assumption that the source and destination states do not change while chezmoi is running"? Or if there are other issues with it?

[halostatue]

It doesn’t violate the assumption any more than the use of lookPath does. You might be able to simplify your call sites a little further:

# .chezmoitemplates/mpv_version_compare
{{- $mpv_version := output "sh" "-c" "mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p'" | trim -}}
{{- semverCompare . $mpv_version -}}

# mpv.conf.tmpl
{{ if includeTemplate "mpv_version_compare" ">=0.34.1" }}
watch-later-options-remove=volume
{{ end }}

This is untested, so it might not work.

[2-4601]

Yeah, that almost works... but as the non-string types seem to get lost, everything needs very explicit conversion:

.chezmoitemplates/mpv_version_compare:

{{- $mpv_version := output "sh" "-c" "mpv --version | sed -n 's/^mpv \\([.0-9]\\{1,\\}\\).*$/\\1/p'" | trim -}}
{{- semverCompare . $mpv_version | int -}}

mpv.conf.tmpl:

{{ if includeTemplate "mpv_version_compare" ">=0.34.1" | int }}
watch-later-options-remove=volume
{{ end }}

[bradenhilton]

Your mpv_version template is easier to reason about than the mpv_version_compare template, IMO.

Also, if you aren't using the $mpv_version variable anywhere else, I think you can just simplify it to

{{ if semverCompare ">=0.34.1" (includeTemplate "mpv_version") }}