feat(os): closes #24655

[litlighilit]

closes #24655

• getHomeDir(username)
• expandTilde supports "~bob".

[litlighilit]

ping @Araq
or the new getHomeDir variant shall be renamed?

[Araq]

The code is ugly.

[litlighilit]

but that's how CPython implemented it (if you refer to body of getHomeDir(username: string)?)

[Araq]

Why would I care how CPython does things... We need to live with this code for good, so clean it up so that the control flow doesn't look like it came from hell.

[litlighilit]

Why would I care how CPython does things...

Sure. I just mean there's an implementation doing so, which has alreadly reviewed by many contributors

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clean it up so that the control flow doesn't look like it came from hell.

If referring to the condition compile branch,
I never wanna make it a hell either... But it's the fact that:

1. some posix like Mac lacks SC_GETPW_R_SIZE_MAX
2. some platform lacks dynamic memory allocate functions.

Also I used to have a try but have no idea.
Pointing out which part requires amend would be helpful.