fixed: last file terminating newline

[ncaq]

From POSIX.
Text file terminating newline.
project-template had bug to no newline last file of hsfiles.
Because, files split by two newline.
But, last file have one newline, Do not two newline.
This commit compatibility omit existing hsfiles.
hsfiles last file do not need to have two newline, and get POSIX text file by this commit.

[snoyberg]

I'm sorry, but I'm having trouble understanding the bug report. The current version of the format allows you to create an hsfiles either with or without the trailing endline. I don't see any violation of a POSIX spec in this, the author of a file has control over how this is rendered.

[ncaq]

For example, case new-template.

% stack new foobar

And you open the .gitignore

% emacs foobar/.gitignore

This file don't terminating newline.
This file is not POSIX file.

Because, other file split of two newline in hsfiles.

For example,

{-# START_FILE Setup.hs #-}
import Distribution.Simple
main = defaultMain

{-# START_FILE test/Spec.hs #-}
main :: IO ()
main = putStrLn "Test suite not yet implemented"

However, last hsfile file is not have two newline.

I think to fix to commercialhaskell/stack-templates: Project templates for stack new.
However, this is trouble.
And, some text editor(Emacs whitespace-mode…) wrong to two newline at file last.

Should I fix to stack-templates or what?

[snoyberg]

I haven't checked this myself yet, but doesn't this patch force a trailing newline on binary content files as well? Files like images should definitely not have such a character appended.

I lean towards modifying the templates themselves instead of the library.

[ncaq]

Files like images should definitely not have such a character appended.

I think to base64 ignore newline.

> B64.decodeLenient "abc"
"i\183"
> B64.decodeLenient "abc\n"
"i\183"
> B64.decodeLenient "abc\n\n\n"
"i\183"

The base64 spec allow newline in body.
Because, email limit width character.

---

I do not care about how to resolve the POSIX file problem.
You can fix it by modifying stack-templates.
However, since many text editors eliminate useless line breaks, it is difficult for authors to be careful one by one.

[snoyberg]

This does in fact break idempotence for textual files:

{-# LANGUAGE OverloadedStrings #-}
import Text.ProjectTemplate
import Conduit
import qualified Data.ByteString as B
import Control.Monad.Writer

main :: IO ()
main = do
  let orig = "hello"
  bs <- runConduit $ yield ("text", return orig) .| createTemplate .| foldC
  m <- execWriterT $ runConduit $ yield bs .| unpackTemplate receiveMem id
  print m

Results in:

fromList [("text","hello\n")]

Note that an extra newline has been appended. Ultimately, this comes down to the fact that the change you're proposing provides no way to handle the case where a textual file doesn't have a trailing newline. You may claim that this shouldn't be allowed, but nonetheless this breaks all existing templates that use text files and correctly encode the trailing newline.

[snoyberg]

Actually, I just realized that the original test suite caught this bug, and your changes simply hide the bug: https://github.com/fpco/haskell-ide/pull/3/files#diff-891fa61a464b745f131591522cdd6dfbR30.

[ncaq]

OK, I respect compatibility.
This pull request close.
We should fix to stack-templates.