Allow partial culture matching in Update-Help

[dkaszews]

PR Summary

Allows the help locale to match, if it is in the list of parents (fallback chain) of the provided (or implicit) one.

Fixes #18021

PR Context

Currently, if the help has locale 'en-US' as most do, only the following will work and everything else will throw an error:

> Update-Help -UICulture 'en-US'
> Update-Help  # when system's culture is also "en-US"

The PR changes it so that the following will also work:

> Update-Help -UICulture 'en'
> Update-Help  # when system's culture is 'en' or child of 'en', because system culture also uses fallback chain

Explicit Update-Help -UICulture 'en-GB' will still not work, because explicit culture does not use fallback chain.

This solves the bug of fallback chain not actually working, as fallback culture 'en' did not match anything. It was supposed to work by use of globbing, but lack of + "*" meant that the glob still used exact matching. It also allows the user to use explicit -UICulture 'en' to mean "any English will do, regardless of region".

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[dkaszews]

There is a single test failing, looks like some empty case for Save-Help I will have to investigate.

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Label      : Small
Size       : +58 -21
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Total files changed: 5

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.cs : +23 -20
.ps1 : +35 -1

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[dkaszews]

Looks like the failing test case was because of a typo in AfterEach { SetTestHook("nmae", $value) }, as it ignores any hook whose name it cannot find. What is the reasoning behind it? Can I make a non-breaking change for it to return fieldInfo != null; saying if it successfully set or not, that the caller can then check, or should I avoid making changes not strictly related to this change?`

[iSazonov]

or should I avoid making changes not strictly related to this change?`

Unrelated and style changes should be moved to separate PRs.

[ghost]

This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

[dkaszews]

@adityapatwardhan Can I please get this one reviewed? I previously got approve from you on #17780 , this one is related. Getting a bit dusty 😅

[daxian-dbw]

@adityapatwardhan Can you please review this PR?

[ghost]

This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

[doctordns]

I will bring this up in the next Cmdlet WG meeting this week. No promises, but I'll try!

[doctordns]

The Cmdlet working group has reviewed this PR and agrees with the proposed behaviour. There is possibly a wider discussion to be had over help fallback culture in general.

[adityapatwardhan]

One of the issues is that on Ubuntu 20+, the default culture is set as C.UTF-8.
It doesn't have 'en' in its parent chain. Can we accommodate for cases like that? If a matching culture is not found fallback to en-US?

[dkaszews]

@adityapatwardhan Interesting case, but out of scope. From my skimming of the POSIX standard, C.UTF-8 is more of a default null culture and in no way equivalent to en-US. In fact, presuming everyone uses en-US is the very source of the issues I am attempting to fix.

Source issue shows the error that will be shown, I think it is well good enough:

Update-Help: Failed to update Help for the module(s) 'Microsoft.PowerShell.Core' with UI culture(s) {C}:
Unable to retrieve the HelpInfo XML file for UI culture C.
Make sure the HelpInfoUri property in the module manifest is valid or check your network connection and then try the command again..
English-US help content is available and can be installed using: Update-Help -UICulture en-US.

I could specialise the error message to also show something like "Your culture is C.UTF-8, which is a default not associated with any language, consider changing your system culture", but please create another issue for it so that it can be discussed.

[adityapatwardhan]

I think the updated error message is much better than the current one. It would be great if you could do that. I will open a issue for that.

[adityapatwardhan]

Here: #19633

[adityapatwardhan]

@dkaszews Thank you for your contribution!

[sdwheeler]

@dkaszews @adityapatwardhan Can one of you file a docs issue for this change?

Use https://github.com/MicrosoftDocs/PowerShell-Docs/issues/new?assignees=&labels=issue-doc-idea%2Cneeds-triage&projects=&template=03-change.yml

[dkaszews]

Created MicrosoftDocs/PowerShell-Docs#10148

[ghost]

🎉v7.4.0-preview.4 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes