Add string matching helper functions to Go templates

In a gh extension (written in bash) I needed to implement a fuzzy matching on the content of a label. Specifically I needed to exclude issues which has a label with project: prefix. However, I couldn't find any functions in https://github.com/cli/go-gh/blob/trunk/pkg/template/template.go or standard go templates to support startsWith.

There are quite a few string related function in https://github.com/Masterminds/sprig including the function which would help in my case:

contains
hasPrefix
hasSuffix
regexMatch

If inclusion of sprig into go-gh is not an option, would it be possible to implement at least contains in the pkg/template/template.go?

@iilyak

@iilyak Thanks for writing in. Is the extension that you are working on written in bash? This repo is for the go-gh Go package which can be used by gh extensions written in Go. If you want commands from gh to support these template functions this issue is more suited for the cli/cli repo where this would need to be addressed.

Is the extension that you are working on written in bash? This repo is for the go-gh Go package which can be used by gh extensions written in Go. If you want commands from gh to support these template functions this issue is more suited for the cli/cli repo where this would need to be addressed.

The cli/cli calls out into go-gh to handle template rendering here (template module is imported here). For the context I am trying to do something similar to https://github.com/samcoe/gh-triage/blob/main/gh-triage

    {{- range $index, $label := $issue.labels -}}
      {{- if not $found -}}
        {{- if eq $label.name "p1" "p2" "p3" "core" "help wanted" "tracking issue" "needs-design" "blocked" "needs-user-input" -}}
          {{- $found = true -}}
        {{- end -}}
      {{- end -}}
    {{- end -}}

However in my case all labels in the condition would be prefixed with project:. So it would look like:

    {{- range $index, $label := $issue.labels -}}
      {{- if not $found -}}
        {{- if hasPrefix $label.name "project:" -}}
          {{- $found = true -}}
        {{- end -}}
      {{- end -}}
    {{- end -}}

@iilyak

@iilyak Thank you for the feature request! Agreed that adding some string helpers would be really helpful.

Related: #5976 (reply in thread)

hello,
if you know your prefix and its exact length, would the following fit your use case ?

# posted by iilyak
{{- if hasPrefix $label.name "project:" -}}

# printf
{{- if eq (printf "%.8s" $label.name) "project:" -}}

💁

@iamazeem

@iamazeem Thanks for opening a PR for this and being patient while we review and discuss! ❤

I've discussed this with @jtmcg and we want to change the expected output for this. We believe this would be better implemented in go-gh instead of cli/cli so extension authors might benefit from it as well.

We think this might go here: https://github.com/cli/go-gh/blob/13104ed7b2db4b8c1a83de4248ddfaaab7682916/pkg/template/template.go#L36

@iamazeem

@iamazeem & anyone else reading: The team has been continuing to discuss this, and we also want this work to limit the functions we import from sprig to the functions requested in this issue:

contains

hasPrefix

hasSuffix

regexMatch

We think that importing all the functions is a bit more "unknown" surface area than what we are comfortable with.

This filtering would likely be done by calling GenericFuncMap() to get all the functions from sprig then filter it before piping it in to template.FuncMap() from Go's built-in "text/template" package like sprig does in its TxtFuncMap().

@BagToad

@iamazeem & anyone else reading: The team has been continuing to discuss this, and we also want this work to limit the functions we import from sprig to the functions requested in this issue:

contains

hasPrefix

hasSuffix

regexMatch

We think that importing all the functions is a bit more "unknown" surface area than what we are comfortable with.

This filtering would likely be done by calling GenericFuncMap() to get all the functions from sprig then filter it before piping it in to template.FuncMap() from Go's built-in "text/template" package like sprig does in its TxtFuncMap().

@BagToad: Sounds good to me. 👍
Importing all the functions won't be as straightforward due to the conflict with the existing functions:

`go-gh`	`sprig`
`join`	`join`
`pluck`	`pluck`
`timeago`	`ago`
`timefmt`	`date`
`truncate`	`trunc`

Not all of these sprig equivalents exactly map to go-gh so it won't be a drop-in replacement i.e. a breaking change w.r.t. UX.

@BagToad

@BagToad: PR cli/go-gh#184 created. Please review. Thanks!

This is fixed by cli/go-gh#184, but will be available when a new release for cli/go-gh is imported into cli/cli.

@BagToad

This is fixed by cli/go-gh#184, but will be available when a new release for cli/go-gh is imported into cli/cli.

@BagToad: May need to update the help text for gh formatting accordingly for the supported sprig functions:

$ gh formatting
...
The `--template` flag requires a string argument in Go template syntax, and will only print
those JSON values which match the query.
In addition to the Go template functions in the standard library, the following functions can be used
with this formatting directive:
- `autocolor`: like `color`, but only emits color to terminals
- `color <style> <input>`: colorize input using <https://github.com/mgutz/ansi>
- `join <sep> <list>`: joins values in the list using a separator
- `pluck <field> <list>`: collects values of a field from all items in the input
- `tablerow <fields>...`: aligns fields in output vertically as a table
- `tablerender`: renders fields added by tablerow in place
- `timeago <time>`: renders a timestamp as relative to now
- `timefmt <format> <time>`: formats a timestamp using Go's `Time.Format` function
- `truncate <length> <input>`: ensures input fits within length
- `hyperlink <url> <text>`: renders a terminal hyperlink
...

@iamazeem

Ah yes! Good call @iamazeem. I'm going to re-open this issue with the expected output being:

gh formatting help text is updated to reflect the new sprig functions implemented in Integrate sprig library go-gh#184
cli/cli's go-gh version is updated (blocked on a new go-gh release, I'll set a reminder to create the go-gh release on Monday next week)

@andyfeller

Delaying the next go-gh release a bit as we have a few other go-gh changes in the pipeline & we want to reduce version churn for go-gh consumers.

cc @andyfeller

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Add string matching helper functions to Go templates #6370

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Add string matching helper functions to Go templates #6370

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samcoe commented on Sep 28, 2022

iilyak commented on Sep 28, 2022

mislav commented on Sep 29, 2022

LangLangBart commented on Sep 29, 2022

BagToad commented on Feb 19, 2025

BagToad commented on Feb 20, 2025

iamazeem commented on Feb 20, 2025

iamazeem commented on Feb 20, 2025

BagToad commented on Mar 7, 2025

iamazeem commented on Mar 7, 2025

BagToad commented on Mar 7, 2025

BagToad commented on Mar 10, 2025

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