[GHC] #9789: Make GHC accept .format+lhs as extension for literate haskell files

[GHC]

#9789: Make GHC accept .format+lhs as extension for literate haskell files
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              Reporter:  merijn      |            Owner:  merijn
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.9
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by merijn):

 Thanks for the comments.

 Replying to [comment:1 thomie]:
 > * This proposal could use a [wiki:WorkingConventions/AddingFeatures wiki
 page] I think. It would describe the problem being addressed, the
 different proposals that were made, and why this solution was chosen
 (accepting `.format+lhs` as a file extension).

 Given the lack of objection the two times this was raised on the mailing
 list and the triviality of the implementation, I didn't think a separate
 write-up was necessary, but I'll add one and raise this again on the
 mailing list.

 > * Maybe some combination of `-o` and
 [https://www.haskell.org/ghc/docs/7.8.3/html/users_guide/modes.html
 #overriding-suffixes  -x] command line options could be used to get the
 same effect?

 This seems like it'd be tricky if people have repositories containing
 files with different content and in general a bit of a hassle, but it
 would probably work.

 > * This [https://www.haskell.org/pipermail/glasgow-haskell-
 users/2014-March/024757.html mail] (proposing `.hs.format`) and
 [https://www.haskell.org/pipermail/glasgow-haskell-
 users/2014-March/024747.html this one] (prososing a textual fingerprint in
 the module itself) never got a reply.

 Hmm, you're right that .lhs.format should work, since the lack of .lhs
 suffix should avoid it from colliding with JHC's naming. I don't think the
 textual fingerprint in the module itself is a good option, as not all
 formats may allow for this.

 > * How does this feature interact with
 [https://www.haskell.org/ghc/docs/latest/html/users_guide/separate-
 compilation.html boot files]: "Currently, if you use a literate source
 file A.lhs you must also use a literate boot file, A.lhs-boot; and vice
 versa."

 As-is I was simply planning to map the boot file for "lhs+md" to "lhs+md-
 boot".

 > * How does this change affect other compilers (JHC was mentioned)?

 The report does not specify any specific way of mapping modules to
 filenames and as such there is no way to make name resolution portable
 across compilers anyway. My initial email suggested
 standardising/formalising naming in the report, but this was not taken up.

 > * Would this change need to go into a feature language report? Is it a
 language feature, does it need a flag? (I'm just trying to think if this
 change is a big deal or not, maybe I am overthinking things.)

 See previous point, the report explicitly does *not* specify the naming of
 files/modules and as such GHC can implement whatever it likes.

 Replying to [comment:2 thomie]:
 > * Does this break any tools that expect a "normal" file extension (i.e.
 file.lhs), like maybe Github's [https://github.com/github/linguist
 linguist]?

 I would not call this "breaking tools" as the old .lhs extension will
 remain supported by GHC. I would merely say that not all tools may
 immediately *support* this new format. However, it seems unlikely tools
 will change to match a format until GHC implements (i.e., chicken and egg
 problem). I think GHC should just implement a solution that will be easy
 for other tools to follow.

 > * Would `filepath` need to be made aware of this change? Currently:
 > {{{
 > System.FilePath> takeExtension "file.format+lhs"
 > ".format+lhs"
 > }}}

 No, I consider ".format+lhs" to be the extension. This would only change
 the way GHC searched for modules.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9789#comment:3>
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