[GHC] #12851: Regression: GHC doesn't show filepaths by default anymore

[GHC]

#12851: Regression: GHC doesn't show filepaths by default anymore
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           Reporter:  hvr            |             Owner:
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:  8.2.1
          Component:  Compiler       |           Version:  8.1
           Keywords:  regression     |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Sorry for chiming in so late, I didn't notice #12807 and I didn't build
 GHC HEAD for several days, otherwise I would have cried out loud sooner.

 I'm deliberately declaring this a regression since I consider this a bad
 default. And not for the mere fact that change is bad ;-)

 Don't get me wrong, I can see usefulness in the `-fno-show-source-paths`
 feature (although I consider it inconsistent, see below), but it's a bad
 default because in my workflows I rely on seeing the source-path ''by
 default'', and I see no way to restore this as the default behaviour of
 GHC short of patching GHC.


 {{{
  [1 of 1] Compiling Control.Concurrent.STMSupply (.hs -> .o)
 }}}

 First of all, if we drop filepaths, then please drop them completely,
 either I need more information about which `.hs` file was used as source,
 or I don't need it at all, so this ` (.hs -> .o)` suffix is just noise to
 me; not the least because the `-> .o` part carries almost no information
 for me. If the premise of `-fno-show-source-paths` is that we know how we
 called GHC and thereby know what is being compiled, showing `(.hs -> .o)`
 is pointless.

 Morever, `-f(no-)show-source-paths` is a lie/misnomer, as it doesn't only
 control the *source* path display, but *also* the *output* path display!

 Also, when invoking GHC, and pass it multiple include folders, sometimes
 GHC picks up the wrong module (or rather one I didn't intend), having it
 print the source file path by default has been a big timesaver to me,
 detecting when I was barking up the wrong source-file while figuring out
 why stuff didn't work.

 Finally, this also breaks my shell-based workflow because I'm used to
 copy'n'paste filepaths from GHC's output, especially for longer source-
 paths where tab-completing my way to the source path is too tedious.

 This is just the first impression I got while being exposed to this UI
 change today, there may be other regressions I'd notice when having to use
 this for longer.

 So, in summary I propose to

  - Make `-fshow-source-paths` the default again
  - drop the `(.hs->.o)` suffix in `-fno-show-show-source-paths`
  - consider a better name; actually, I can see cases where you want to
 omit only the output-path display (since it's imho often less interesting
 to know the output files names; even though sometimes you may want to know
 it since it can be affected in a non-obvious way by output-dir flags),
 e.g. maybe
     - Have `-f(no-)show-source-paths` control the source-path display
     - Have `-f(no-)show-output-paths` control the output-path display
     - As a compromise, consider `-fshow-source-paths -fno-show-output-
 paths` becoming the new default.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12851>
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