Run the build with 3 latest GHC versions

.buildkite/pipeline.yml

@@ -1,7 +1,18 @@
 steps:
-  - label: Build and test
+  - label: Build and test with GHC 8.6.5
+    command: |
+      nix-build --keep-going --no-out-link --argstr ormoluCompiler ghc865
+    timeout: 100
+  - label: Build and test with GHC 8.8.3
+    command: |
+      nix-build --keep-going --no-out-link --argstr ormoluCompiler ghc883
+    timeout: 100
+  - label: Build and test with GHC 8.10.1
+    command: |
+      nix-build --keep-going --no-out-link --argstr ormoluCompiler ghc8101
+    timeout: 100
+  - wait
+  - label: Check formatting
     command: |
-      nix-build --keep-going --no-out-link
       ./format.sh
       git diff --exit-code --color=always
-    timeout: 100

default.nix

@@ -1,7 +1,8 @@
-{ pkgs ? (import ./nix/nixpkgs) }:
+{ pkgs ? (import ./nix/nixpkgs)
+, ormoluCompiler ? "ghc883" # the shell doesn't work with ghc8101 yet
+}:
 
 let
-  ormoluCompiler = "ghc865";
   source = pkgs.lib.sourceByRegex ./. [
     "^.*\.md$"
     "^app.*$"
@@ -14,16 +15,12 @@ let
     overrides = ormoluOverlay;
   };
   ormoluOverlay = self: super: {
-    "ormolu" = pkgs.haskell.lib.enableCabalFlag
-      (super.callCabal2nix "ormolu" source { }) "dev";
-    # Nixpkgs provides ghc-lib-parser-8.8.0.20190424, but we want
-    # ghc-lib-parser-8.10.1. We disable Haddock generation because it's way
-    # too slow.
+    "ormolu" = super.callCabal2nixWithOptions "ormolu" source "-fdev" { };
     "ghc-lib-parser" = pkgs.haskell.lib.dontHaddock
       (super.callHackageDirect {
         pkg = "ghc-lib-parser";
-        ver = "8.10.1.20200324";
-        sha256 = "0f2c68fzdj2lw6da2zpx7a0cx631im3kylwd85dzx1npsm1vzlbg";
+        ver = "8.10.1.20200412";
+        sha256 = "sha256-EjMzp8xRT3xVFKDI1fAfopkylGB0hv35Av2+uZeETRU=";
       } {});
   };
   ormolize = import ./nix/ormolize {
@@ -51,15 +48,22 @@ let
     }) haskellPackages;
 in {
   ormolu = haskellPackages.ormolu;
-  ormoluShell = haskellPackages.shellFor {
-    packages = ps: [
-      ps.ormolu
-    ];
-    buildInputs = [
-      haskellPackages.cabal-install
-      haskellPackages.ghcid
-    ];
-  };
+  ormoluShell =
+    if ormoluCompiler == "ghc8101"
+      # HACK The shell doesn't compile with GHC 8.10.1
+      then haskellPackages.shellFor {
+        packages = ps: [];
+        buildInputs = [];
+      }
+      else haskellPackages.shellFor {
+        packages = ps: [
+          ps.ormolu
+        ];
+        buildInputs = [
+          haskellPackages.cabal-install
+          haskellPackages.ghcid
+        ];
+      };
   withOrmolu = haskellPackages.shellFor {
     packages = ps: [];
     buildInputs = [
@@ -81,7 +85,6 @@ in {
       "cryptonite"
       "diagrams-core"
       "distributed-process"
-      "esqueleto"
       "fay"
       "hakyll"
       "haxl"
@@ -98,6 +101,10 @@ in {
       "tls"
       "yesod-core"
 
+      # Uses CPP to concatenate strings in a deprecation annotation
+
+      # "esqueleto"
+
       # Comment idempotence issue
 
       # "Agda"

nix/nixpkgs/default.nix

@@ -1,6 +1,6 @@
 let
-  rev = "19.09";
-  sha256 = "0mhqhq21y5vrr1f30qd2bvydv4bbbslvyzclhw0kdxmkgg3z4c92";
+  rev = "807ca93fadd5197c2260490de0c76e500562dc05";
+  sha256 = "10yq8bnls77fh3pk5chkkb1sv5lbdgyk1rr2v9xn71rr1k2x563p";
   nixpkgs = builtins.fetchTarball {
     url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
     inherit sha256;

src/Ormolu/Parser/Pragma.hs

@@ -10,7 +10,7 @@ where
 
 import Control.Monad
 import Data.Char (isSpace, toLower)
-import Data.List
+import qualified Data.List as L
 import qualified EnumSet as ES
 import FastString (mkFastString, unpackFS)
 import qualified Lexer as L
@@ -35,8 +35,8 @@ parsePragma ::
   String ->
   Maybe Pragma
 parsePragma input = do
-  inputNoPrefix <- stripPrefix "{-#" input
-  guard ("#-}" `isSuffixOf` input)
+  inputNoPrefix <- L.stripPrefix "{-#" input
+  guard ("#-}" `L.isSuffixOf` input)
   let contents = take (length inputNoPrefix - 3) inputNoPrefix
       (pragmaName, cs) = (break isSpace . dropWhile isSpace) contents
   case toLower <$> pragmaName of
@@ -46,7 +46,7 @@ parsePragma input = do
     _ -> Nothing
   where
     trimSpaces :: String -> String
-    trimSpaces = dropWhileEnd isSpace . dropWhile isSpace
+    trimSpaces = L.dropWhileEnd isSpace . dropWhile isSpace
 
 -- | Assuming the input consists of a series of tokens from a language
 -- pragma, return the set of enabled extensions.

src/Ormolu/Printer/Meat/Declaration.hs

@@ -164,7 +164,7 @@ p_instDecl style = \case
 
 p_derivDecl :: DerivDecl GhcPs -> R ()
 p_derivDecl = \case
-  d@DerivDecl {..} -> p_standaloneDerivDecl d
+  d@DerivDecl {} -> p_standaloneDerivDecl d
   XDerivDecl x -> noExtCon x
 
 -- | Determine if these declarations should be grouped together.

src/Ormolu/Printer/Operators.hs

@@ -11,7 +11,7 @@ module Ormolu.Printer.Operators
 where
 
 import Data.Function (on)
-import Data.List
+import qualified Data.List as L
 import Data.Maybe (fromMaybe, mapMaybe)
 import Data.Ord (Down (Down), comparing)
 import GHC
@@ -105,7 +105,7 @@ buildFixityMap ::
 buildFixityMap getOpName opTree =
   concatMap (\(i, ns) -> map (\(n, _) -> (n, fixity i InfixL)) ns)
     . zip [0 ..]
-    . groupBy (doubleWithinEps 0.00001 `on` snd)
+    . L.groupBy (doubleWithinEps 0.00001 `on` snd)
     . (overrides ++)
     . modeScores
     $ score opTree
@@ -143,22 +143,22 @@ buildFixityMap getOpName opTree =
     -- Pick the most common score per 'RdrName'.
     modeScores :: [(RdrName, Double)] -> [(RdrName, Double)]
     modeScores =
-      sortOn snd
+      L.sortOn snd
         . mapMaybe
           ( \case
               [] -> Nothing
               xs@((n, _) : _) -> Just (n, mode $ map snd xs)
           )
-        . groupBy ((==) `on` fst)
-        . sort
+        . L.groupBy ((==) `on` fst)
+        . L.sort
     -- Return the most common number, leaning to the smaller
     -- one in case of a tie.
     mode :: [Double] -> Double
     mode =
       head
-        . minimumBy (comparing (Down . length))
-        . groupBy (doubleWithinEps 0.0001)
-        . sort
+        . L.minimumBy (comparing (Down . length))
+        . L.groupBy (doubleWithinEps 0.0001)
+        . L.sort
     -- The start column of the rightmost operator.
     maxCol = go opTree
       where