Language Pragmas Auto-Insert After Module Docs

[emilypi]

Your environment

Output of haskell-language-server --probe-tools or haskell-language-server-wrapper --probe-tools:

haskell-language-server version: 1.1.0.0 (GHC: 8.10.4) (PATH: /Users/emilypi/.ghcup/bin/haskell-language-server-wrapper-1.1.0) (GIT hash: f1c096927186a93d8e3ccd4fe8385cc1b070350b)
Tool versions found on the $PATH
cabal:		3.4.0.0
stack:		2.5.1
ghc:		8.10.4

Which OS do you use:
Big Sur OSX

Which lsp-client do you use:
Emacs lsp-haskell
Describe your project (alternative: link to the project):
Cabal project
Contents of hie.yaml:

cradle:
  cabal:
    - path: "Cabal/src"
      component: "lib:Cabal"

    - path: "cabal-install/src"
      component: "lib:cabal-install"

    - path: "cabal-install/main/Main.hs"
      component: "cabal-install:exe:cabal"

    - path: "cabal-install/tests"
      component: "cabal-install:test:unit-tests"

    - path: "cabal-install/tests"
      component: "cabal-install:test:memory-usage-tests"

    - path: "cabal-install/tests"
      component: "cabal-install:test:integration-tests2"

    - path: "cabal-install/tests"
      component: "cabal-install:test:long-tests"

    - path: "cabal-install-solver/src"
      component: "lib:cabal-install-solver"

    - path: "cabal-install-solver/src-assertion"
      component: "lib:cabal-install-solver"

Steps to reproduce

On HLS 1.1, auto-insert any language pragma in a module with header documentation

Expected behaviour

Pragmas should be inserted before docs

Actual behaviour

Pragmas are inserted after docs:

{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE DeriveFoldable #-}
{-# LANGUAGE DeriveTraversable #-}
-- | Cabal-like file AST types: 'Field', 'Section' etc,
--
-- This (intermediate) data type is used for pretty-printing.
--
-- @since 3.0.0.0
--
{-# LANGUAGE LambdaCase #-}
module Distribution.Fields.Pretty 

[OliverMadine]

I believe that the intended behaviour is to insert pragmas directly before the start of the first line of Haskell code, this is done using the following:

endOfModuleHeader :: ParsedModule -> Range
endOfModuleHeader pm =
  let mod = unLoc $ pm_parsed_source pm
      modNameLoc = getLoc <$> hsmodName mod
      firstImportLoc = getLoc <$> listToMaybe (hsmodImports mod)
      firstDeclLoc = getLoc <$> listToMaybe (hsmodDecls mod)
      line = maybe 0 (_line . _start) (modNameLoc <|> firstImportLoc <|> firstDeclLoc >>= srcSpanToRange)
      loc = Position line 0
   in Range loc loc

We could include an option to always insert pragmas at the top of the file? I will open a PR for this shortly.

[jneira]

I am afraid there was a pr that remove just that behaviour cause it put the pragma before she-bangs: #1340 which fixed #555
I think the ideal behaviour should be identify the code span of the last pragmas block (as we could have several pragmas blocks with comments between them) and insert the new one just after it