Fix os.tmpdir bug

[BYK]

The checked method on os module was tempDir which was not existing on any version of Node (should have been tmpDir). With Node 0.10, the name became tmpdir.

[nfischer]

I agree, it looks like it should say tmpDir, not tempDir. With v5.3.0 I can see both tmpDir and tmpdir. Is there a difference in this case?

Could you provide an example of buggy behavior and the expected behavior?

[BYK]

@nfischer - you can check the ticket on ESLint that refers to this one: eslint/eslint#4061

In short, instead of using the built-in tmpDir functionality, it falls back to the manual temporary directory creation which is prone to errors.

[nfischer]

After looking into things a bit, I agree with the change of os.tempDir -> os.tmpDir. However, I think that os.tmpDir is exactly equivalent to os.tmpdir (see the current source code, the archived source, and the stack overflow post that lead me there).

Unless there's discussion of getting rid of os.tmpDir in favor of os.tmpdir, we should probably only keep os.tmpDir (if this name is deprecated though, I think it's better to include both).

Other than that, this looks like something we would merge fairly soon.

[BYK]

@nfischer I also double checked from my console in Node 4 and os.tmpdir === os.tmpDir returns true. That said the docs make no mention of this: https://nodejs.org/api/os.html#os_os_tmpdir

So my suggestion is either dropping the undocumented tmpDir version and also drop Node 0.8 support which is quite old, or keeping it as it is, for the sake of clarity. (we may add a comment linking back to this discussion).

[nfischer]

Ok, you raise a good point about it being undocumented. Since this operation should only be performed once (and the result will be cached), it shouldn't bloat things too much. A comment linking back might be a good (plus, it'll trigger the CI so we can verify that it doesn't break things).

LGTM, once the CI passes

[nfischer]

@ariporad what are your thoughts?

[ariporad]

@nfischer: I'm not sure I understand this 100%, but I think that the best thing to do would be (os.tempDir || os.tmpDir || os.tmpdir)(...).

[nfischer]

@ariporad os.tempDir doesn't actually exist (it was a typo I think).

You suggestion works if at least one of the three functions exists. The issue is that early versions (before 0.8) don't have any of those functions. So if os.tempDir and os.tmpDir don't exist, it'll always call os.tmpdir() (which doesn't always exist).

If we do it in multiple lines as it is, it will never call the function unless it actually exists (so the code works as expected).

As this PR is written, it fixes the typo (which is good), and it prefers the newer (and actually documented) name os.tmpdir over os.tmpDir, which is probably a safer bet in the long run.

[ariporad]

@nfischer: Then LGTM!