export Base.withenv

[stevengj]

As discussed in #10836, this exports Base.withenv (renamed from with_env for consistency with setenv); it now takes zero or more var=>val arguments to specify the changes to the environment.

For consistency, I added a setenv method taking var=>val arguments (Pair...). However, the main usage pattern for setenv seems to be to copy(ENV) and modify/set one environment variable. Maybe setenv should be deprecated entirely in favor of withenv?

Note also that the setenv test results weren't actually being checked.

[StefanKarpinski]

Looks great.

[tkelman]

I think this last one's going to fail on windows

[stevengj]

Maybe dir=".." instead of /?

[stevengj]

All of the uses of setenv that I can find in the packages are of the copy(ENV) pattern that would seem better served by withenv:

• SCS, cc @mlubin
• DataFrames, cc @tkelman
• CoinOptServices, cc @tkelman
• JuliaPackaging/BinDeps.jl@784716b, cc @Keno

Theoretically, setenv has the advantage of allowing you to easily completely replace the environment, but it's not clear to me when or why anyone would ever use it this way. But Python exports a similar function, so I guess we might as well continue to export this functionality from libuv?

[GlenHertz]

I use setenv to configure minimal environments and find it useful.

[tkelman]

At the least the way in which setenv currently works, returning a modified Cmd object from the input Cmd object is pretty useful. I think only the DataFrames example above would be able to effectively use this do-block withenv construct, maybe unless you were to wrap the entire BinDeps invocation in the do block.

[stevengj]

Okay.

[JeffBezanson]

I do dislike underscores, but I feel the need to mention that we have with_rounding. We should discuss what the naming convention should be for functions like this.

[StefanKarpinski]

Related:

• the idea of having a with keyword, Python style and doing resource cleanup by providing methods on an object type like a file handle or a environment type.
• the idea of having defer keyword, Go/D style and doing resource cleanup whenever unwinding the stack.