haskell-cabal-add-dependency messes up cabal file if tabs are not turned off.

[rabipelais]

I am attempting to add a dependency automatically to a cabal file. However, after the insertion, the cabal file is completely broken. This happens if indent-tabs-mode is set to true, even if it is set to false for haskell-cabal mode.

Steps to reproduce

Start with default auto-generated minimal cabal file.
With that file in the current buffer run:
(setq-default indent-tabs-mode t)
(haskell-cabal-add-dependency "foo" "3" nil nil)
Answer yes to prompts

Expected result

name:                test
version:             0.1.0.0
license-file:        LICENSE
build-type:          Simple
cabal-version:       >=1.10

executable test
  main-is:             Main.hs
  build-depends:  foo >= 3
                 , base >=4.7 && <4.8
  default-language:    Haskell2010

Actual result

name:                test
version:             0.1.0.0
license-file:        LICENSE
build-type:          Simple
cabal-version:       >=1.10

executable test
  main-is:             Main.hs
  build-depends:                           foo >= 3
                     , 4.8
  default-language:    Haskell2010

Note that the weird indentation and lack of base is verbatim copied from my editor. The whitespace between build-depends: and foo is tabs, not spaces.

Notes

As mentioned above, this happens if tabs are turned on, even if they are turned off for all haskell related modes. Adding more dependencies after this only makes the file wonkier.
If I undo the (haskell-cabal-add-dependency "foo" "3" nil nil) command, set indent-tabs-mode to nil, and re-add the dependency, it is inserted correctly this time.

[gracjan]

@rabipelais: Is this the same as #376?

[rabipelais]

@gracjan

haskell-cabal-mode explicitly does (setq indent-tabs-mode nil) so I guess a TAB in cabal file will
happen never again.

That solution doesn't work for me in this case, because that (setq indent-tabs-mode nil) applies only to haskell-cabal-mode.
In the use-case where a global indent-tabs-mode is not nil (for example for me, as I use tabs for C/C++ dev), the problem arises when haskell-cabal-add-dependency calls haskell-cabal-with-subsection, which in turn uses the with-temp-buffer macro to temporarily format the new entries. The buffer that with-temp-buffer opens starts in the default major-mode, which is fundamental-mode in the default case.
Here the indent-tabs-mode from the haskell-cabal-mode has no effect, hence the tabs, which are copied verbatim to the cabal file.

I will test if changing indent-tabs-mode inside the with-temp-buffer macro solves the issue.

[rabipelais]

Yes, apparently setting indent-tabs-mode to nil inside with-temp-buffer (and recompiling) solves the issue, with no side-effects.

--- #<buffer haskell-cabal.el>
***************
*** 464,469 ****
--- 464,470 ----
         (save-excursion
           (prog1
               (with-temp-buffer
+                (setq indent-tabs-mode nil)
                 (indent-to ,start-col)
                 (insert ,section-data)
                 (goto-char (point-min))

should I submit a pull request? Or is the change way too small?

[gracjan]

@rabipelais: Change looks good to me and was already discussed in #376.

A pull request would be greatly appreciated.

[gracjan]

@rabipelais: Is this working for you now? Can we close?

[rabipelais]

Yes, working. It can be closed, thank you.

[gracjan]

@rabipelais: You can close this issue yourself as you are the one reporting it!