Fix dropExeExtension on Windows

[DanielG]

On Windows dropExeExtension doesn't actually drop the exe extension.

We have

splitExtension "foo.exe" == ("foo", ".exe")

but the code is expecting just "exe" for the extension field.

Among other things this makes guessToolFromGhcPath behave
unexpectedly. Since takeVersionSuffix can't see past the extension the
null suf case in mkGuesses will trigger which causes the versioned
program path candidates to not be looked for.

---

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.

[DanielG]

So technically this is breaking API compatibility since this is exported, but there don't seem to be any usages outside of Cabal oh hackage: https://codesearch.aelve.com/haskell/search?query=exeExtensions&insensitive=off&space=off&precise=on&sources=on

Furthermore <.> doesn't care about the leading dot in the extension, so "foo" <.> "bar" == "foo" <.> ".bar" == "foo.bar".

[phadej]

tests/UnitTests/Distribution/Simple/Utils.hs:12:27:
    Module `System.Directory' does not export `exeExtension'

on old GHCs. There's exeExtension in Distribution.Simple.BuildPaths though

EDIT: which returns just "exe" on Windows.

[DanielG]

Argh, more CPP needed :) nvm, I can just always use Distribution.Simple.BuildPaths.exeExtension.

[DanielG]

How many revisions can a PR that essentially adds a "." possibly need!? ;-)

[phadej]

Cabal codebase has the following property: if something is not fixed immediately as spotted, it will take years to be spotted again (and this fixed).

…

On 7 Oct 2019, at 11.25, Daniel Gröber (dxld) ***@***.***> wrote: How many revisions can a PR that essentially adds a "." possibly need!? ;-) — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[DanielG]

Well pretty much any codebase has that property ;) That's why I try to shoot patches as soon as I find issues.

[phadej]

tests\UnitTests\Distribution\Simple\Utils.hs:92:33: error:
    * Couldn't match type `Distribution.System.Platform -> String'
                     with `[Char]'
      Expected type: String
        Actual type: Distribution.System.Platform -> String
    * Probable cause: `exeExtension' is applied to too few arguments
      In the second argument of `(<.>)', namely `exeExtension'
      In the first argument of `dropExeExtension', namely
        `("foo" <.> exeExtension)'
      In the first argument of `(==)', namely
        `dropExeExtension ("foo" <.> exeExtension)'
   |
92 |     dropExeExtension ("foo" <.> exeExtension) == "foo"
   |                                 ^^^^^^^^^^^^
cabal.exe: Failed to build test:unit-tests from Cabal-3.1.0.0.

[DanielG]

Travis is green except for Mac, with one timeout and one network error :)