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env::home_dir() should use SHGetKnownFolderPath() on windows. #28940
Description
At the moment, it first looks at %HOME%, and then at %USERPROFILE%. This is bad for two reasons:
-
The home directory will be different when run from an msys or cygwin terminal. Unless the program is specifically compiled to run in an msys/cygwin environment (they have their own target triples) then it should not be affected by
%HOME%(only%USERPROFILE%stores the home directory on windows). -
Environment variables may be overridden.
SHGetKnownFolderPath()will always give the correct path to the user's home folder.
Reacted by Peter Atashian, Kornel, Felipe S. S. Schneider, zohnannor and Eliaz Bobadilla
Activity
FaultyRAM commentedon Oct 10, 2015
Adding to this,
env::temp_dir()also parses environment variables whereSHGetKnownFolderPath()would be more appropriate.barosl commentedon Oct 10, 2015
By looking at the code, it seems that
home_diralready utilizesGetUserProfileDirectory, which is a bit more portable option thanSHGetKnownFolderPath(albeit Rust basically targets Vista, so this won't be much a concern). The thing is,%HOME%and%USERPROFILE%are explicitly checked first before using the Windows API. I guess this is an intended behavior to enable the exact overriding behavior you described (so that you could get the "incorrect" path by setting%HOME%manually), but I'm not very sure. Could you confirm, @alexcrichton?As for
temp_dir, it is already usingGetTempPathto return the appropriate path. The reason why the Rust documentation says it checks the environment variables is that it is exactly the behavior described in MSDN. It states: "The GetTempPath function checks for the existence of environment variables in the following order and uses the first path found". And also,SHGetKnownFolderPathseems to not support the temporary directory.nagisa commentedon Oct 10, 2015
Relevant PR which contains some related discussion.
FaultyRAM commentedon Oct 11, 2015
@barosl Oops, you're right. In that case, I'd say this is bad documentation - not mentioning
GetUserProfileDirectory()seems to be an oversight, and we should be describing the actual behaviour ofenv::get_temp()on Windows even if the effective behaviour is the same as what's described now, because that's not what I expected, and certainly not what others will expect. That and, of course,GetTempPath()could always change or be deprecated in the future, and then the docs would be wrong anyway.barosl commentedon Oct 11, 2015
@FaultyRAM I sent a PR that resolves the documentation issue, please review it: #28960.
Clarify the behavior of `std::env::home_dir` and `std::env::temp_dir`
FaultyRAM commentedon Oct 11, 2015
@barosl Looks good!
Auto merge of #28960 - barosl:home-temp-dir-doc, r=alexcrichton
alexcrichton commentedon Oct 12, 2015
Believe it or not, this behavior has been here since literally the beginning (dafd649) of this module. The fallback to
GetUserProfileDirectorywas added relatively recently (70ed3a4) after it was suggested. I think it's safe to say that this was not highly scrutinized to the point of vetting the implementation as to what it should be.I'll also note that this basically matches what python does as well as what ruby does. My personal opinion is that it's working as intended.
Diggsey commentedon Oct 12, 2015
And in every case it just makes the user experience worse on windows. The convention for getting the home directory on windows is (obviously) to use the helpfully provided OS functions to do so. That's what .net, java and other software does, that has a runtime which is actually written for windows, and is not just a barely functioning wrapper in order to provide a unix-like interface.
At best, the python and ruby interpreters can be slightly let off the hook as they are scripting languages, and so you might expect behaviour to be a little "fuzzy" with respect to the environment. At worst, they're shoving unix-like conventions onto a platform where they don't work or belong.
It's also one of the reasons why msys doesn't try to override the
%USERPROFILE%environment variable: native windows software isn't supposed to change behaviour when run from msys: the only way msys functions properly is if native windows software is oblivious to it.If you want a unix-like environment on windows, then target msys or cygwin - it's what they're there for after all... If you don't, then don't start looking for unix environment variables!
retep998 commentedon Oct 12, 2015
I am personally in favor of disregarding the environment variables entirely and just calling the OS function directly and leaving it at that.
steveklabnik commentedon Mar 1, 2017
nominating so libs can make a call on what's the right behavior here
3 remaining items
retep998 commentedon Mar 14, 2017
What name should the new one have?
user_profile_dir?aturon commentedon Mar 14, 2017
How about
user_dir? Not idiomatic for any of our major platforms, but hopefully gets the idea across?nagisa commentedon Mar 14, 2017
See also #40320
Diggsey commentedon Mar 14, 2017
It seems a shame to have to pick slightly worse names for things each time we deprecate something.
dtolnay commentedon Nov 15, 2017
On the spectrum of acceptable breakage, how bad is changing
home_diron Windows to do the right thing? It seems like we are saying pretty much anything callinghome_diron Windows right now is buggy behavior. Is that fair?droundy commentedon Nov 15, 2017
My vote, for what it's worth, would be to just treat the current behavior on windows as a bug, and fix it. Is anyone aware of rust code that relies on the current Windows behavior?
dtolnay commentedon Nov 19, 2017
Let's get a PR that fixes the bug and go from there.
dtolnay commentedon Jan 29, 2018
We decided against making this change in #46799. #46799 (comment) proposes possible next steps for handling this better in an external crate.
soc commentedon Jun 13, 2018
std::env::home_diris also broken on Linux – is there any chance to get anything fixed at all in this case, or does it make more sense to give up and tell people to roll their own implementation (which I fear will lead to many implementations that lack the platform coverage ofstd::env::home_dir)?tjkirch commentedon Jul 30, 2018
@soc - how is it broken on Linux? I'm trying to figure out why home_dir was deprecated when it's working great for me on Linux.
soc commentedon Jul 30, 2018
@tjkirch #51656 hope this helps.