Base setup for i18n for server with go-i18n library

[Kshitij-Katiyar]

Summary

It includes:

1. Added the go-i18n library v2.
2. Added sample translation and also en.json file

Fixes #783

[mickmister]

LGTM, just a suggestion on wording

[mickmister]

This names seems a bit cryptic to me. Maybe we can call it localization or i18n? @hanzei Thoughts on this?

[hanzei]

Yeah, b isn't quite telling. 2./5 on bundle as i18n is already a library name.

[mickmister]

Curious how we can use the translations in the templates?

[Kshitij-Katiyar]

yeah @mickmister I was trying to find the same thing.

[mickmister]

Can we expose functions to call from within the template?

[mickmister]

I think this is something we should try and solve before merging the PR. Any question marks we have on how to do things like this should ideally be resolved before contributors go and work on the same sort of things

[mickmister]

We can implement this method:

func (p *Plugin) localize(id, other string) string {
	return p.b.LocalizeWithConfig(l, &i18n.LocalizeConfig{
		DefaultMessage: &i18n.Message{
			ID:    id,
			Other: other,
		},
	})
}

---

Then change

mattermost-plugin-github/server/plugin/template.go

Line 38 in e958064

func init() {

to

func (p *Plugin) initTemplates() {

---

and add a block here

mattermost-plugin-github/server/plugin/template.go

Lines 108 to 116 in e958064

	funcMap["commitAuthor"] = func(commit *github.HeadCommit) *github.CommitAuthor {
	if showAuthorInCommitNotification {
	return commit.GetAuthor()
	}
	return commit.GetCommitter()
	}
	masterTemplate = template.Must(template.New("master").Funcs(funcMap).Parse(""))

to

funcMap["i18n"] = p.localize

---

Then we should be able to use the i18n function in the templates

[Kshitij-Katiyar]

Hey @mickmister Thanks for the approach above, I tried a bunch of things as stated above but faced several issues.
First of all, there is a huge lack of documentation and resources on the internet regarding Go's text/template and i was not able to find anything which connects the translation and template together. If you have some resources, please share those i would love to deep dive into those.

First of all, When using higher-order functions inside the template directly, it prints the function returned by the parent function instead of trying to run the child function returned with the arguments passed(similar code here dummy code). I also tried storing the child function in a variable and calling it with the arguments, but that didn't work either. (You can have a link here goPlayground)

Secondly, the approach of making the initTemplate a method of the Plugin also didn't work because, during the initialization of the template, the Plugin is null.

[mickmister]

Secondly, the approach of making the initTemplate a method of the Plugin also didn't work because, during the initialization of the template, the Plugin is null.

@Kshitij-Katiyar We should be able to call initTemplate during OnActivate to make that work

I'm not sure about the template functions behavior

[mickmister]

In order to include localization in templates, we'll need to have the code-operated parts (i.e. markdown link construction) of the message be parameterized into the translation string. We can pass the calculated sub-template calls as a dictionary argument to the localize function

With this in i18n/en.json

{
     "newPullRequestCollapsed": "{{.RepoName}} New pull request {{.PullRequestTitle}} was opened by {{.UserName}}.",
}

func localize(bundle *i18n.Bundle, lang string) func(id string, data map[string]interface{}) string {
    return func(id string, data map[string]interface{}) string {
        localizer := i18n.NewLocalizer(bundle, lang)
        return localizer.MustLocalize(&i18n.LocalizeConfig{
            MessageID:    id,
            TemplateData: data,
        })
    }
}

---

Then we can change

mattermost-plugin-github/server/plugin/template.go

Line 207 in e958064

{{template "repo" .Event.GetRepo}} New pull request {{template "pullRequest" .Event.GetPullRequest}} was opened by {{template "user" .Event.GetSender}}.

to

{{ localize "newPullRequestCollapsed" dict "RepoName" (template "repo" .Event.GetRepo) "PullRequestTitle" (template "pullRequest" .Event.GetPullRequest) "UserName" (template "user" .Event.GetSender) }}

---

Or we could instead make local variables in the template like this for potentially better readability, but we'll need to implement an expose a templateToString function to return a string:

{{ $repo := templateToString "repo" .Event.GetRepo }}
{{ $pullRequest := templateToString "pullRequest" .Event.GetPullRequest }}
{{ $user := templateToString "user" .Event.GetSender }}
{{ localize "newPullRequestCollapsed" dict "RepoName" $repo "PullRequestTitle" $pullRequest "UserName" $user }}

[hanzei]

That is a great starting point!

How can community members contribute to translations? Do we plan to hook the repo up to https://translate.mattermost.com/?

[hanzei]

Yeah, b isn't quite telling. 2./5 on bundle as i18n is already a library name.