Change parsers to use flag' instead of switch

This fixes commercialhaskell#3959.

The problem is that the
[switch](https://hackage.haskell.org/package/optparse-applicative/docs/Options-Applicative-Builder.html#v:switch)
function returns a `Just False` which gets wrapped into `First`.  This
means that the value is *always* set to either `True` or `False` and
the `First` monoid means that during options parsing the order of the
flags suddenly matters as described in commercialhaskell#3959, because `First (Just
False)` is chosen.

The fix is to use the
[flag](https://hackage.haskell.org/package/optparse-applicative-0.14.2.0/docs/Options-Applicative-Builder.html#v:flag-39-)
function that does not set a default value, so we get a `First
Nothing` instead.

src/Stack/Options/BenchParser.hs

@@ -19,7 +19,7 @@ benchOptsParser hide0 = BenchmarkOptsMonoid
                                  help ("Forward BENCH_ARGS to the benchmark suite. " <>
                                        "Supports templates from `cabal bench`") <>
                                  hide))
-        <*> optionalFirst (switch (long "no-run-benchmarks" <>
+        <*> optionalFirst (flag' True (long "no-run-benchmarks" <>
                           help "Disable running of benchmarks. (Benchmarks will still be built.)" <>
                              hide))
    where hide = hideMods hide0

src/Stack/Options/TestParser.hs

@@ -27,12 +27,12 @@ testOptsParser hide0 =
                          help "Arguments passed in to the test suite program" <>
                          hide)))
         <*> optionalFirst
-                (switch
+                (flag' True
                     (long "coverage" <>
                      help "Generate a code coverage report" <>
                      hide))
         <*> optionalFirst
-                (switch
+                (flag' True
                     (long "no-run-tests" <>
                      help "Disable running of tests. (Tests will still be built.)" <>
                      hide))

test/integration/tests/3959-order-of-flags/Main.hs

@@ -0,0 +1,21 @@
+import StackTest
+
+import Control.Monad (unless)
+import Data.List (isInfixOf)
+
+-- Integration test for https://github.com/commercialhaskell/stack/issues/3959
+main :: IO ()
+main = do
+  checkFlagsBeforeCommand
+  checkFlagsAfterCommand
+
+checkFlagsBeforeCommand :: IO ()
+checkFlagsBeforeCommand = stackCheckStderr ["--nix", "--test", "--no-run-tests", "build"] checker
+
+checkFlagsAfterCommand :: IO ()
+checkFlagsAfterCommand = stackCheckStderr ["build", "--nix", "--test", "--no-run-tests"] checker
+
+checker :: String -> IO ()
+checker output = do
+  let testsAreDisabled = any (\ln -> "Test running disabled by" `isInfixOf` ln) (lines output)
+  unless testsAreDisabled $ fail "Tests should not be run"

test/integration/tests/3959-order-of-flags/files/Setup.hs

@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain

test/integration/tests/3959-order-of-flags/files/app/Main.hs

@@ -0,0 +1,6 @@
+module Main where
+
+import Lib
+
+main :: IO ()
+main = someFunc

test/integration/tests/3959-order-of-flags/files/bug3959.cabal

@@ -0,0 +1,61 @@
+-- This file has been generated from package.yaml by hpack version 0.28.2.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: bb372c89031f8c68e9e26d37362cb59adb7915eb2da6333d56da87a83966bb35
+
+name:           bug3959
+version:        0.1.0.0
+description:    Please see the README on GitHub at <https://github.com/githubuser/bug3959#readme>
+homepage:       https://github.com/githubuser/bug3959#readme
+bug-reports:    https://github.com/githubuser/bug3959/issues
+author:         Author name here
+maintainer:     example@example.com
+copyright:      2018 Author name here
+license:        BSD3
+license-file:   LICENSE
+build-type:     Simple
+cabal-version:  >= 1.10
+extra-source-files:
+    ChangeLog.md
+    README.md
+
+source-repository head
+  type: git
+  location: https://github.com/githubuser/bug3959
+
+library
+  exposed-modules:
+      Lib
+  other-modules:
+      Paths_bug3959
+  hs-source-dirs:
+      src
+  build-depends:
+      base >=4.7 && <5
+  default-language: Haskell2010
+
+executable bug3959-exe
+  main-is: Main.hs
+  other-modules:
+      Paths_bug3959
+  hs-source-dirs:
+      app
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , bug3959
+  default-language: Haskell2010
+
+test-suite bug3959-test
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  other-modules:
+      Paths_bug3959
+  hs-source-dirs:
+      test
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , bug3959
+  default-language: Haskell2010

test/integration/tests/3959-order-of-flags/files/src/Lib.hs

@@ -0,0 +1,6 @@
+module Lib
+    ( someFunc
+    ) where
+
+someFunc :: IO ()
+someFunc = putStrLn "someFunc"

test/integration/tests/3959-order-of-flags/files/stack.yaml

@@ -0,0 +1,65 @@
+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+# resolver: ghcjs-0.1.0_ghc-7.10.2
+#
+# The location of a snapshot can be provided as a file or url. Stack assumes
+# a snapshot provided as a file might change, whereas a url resource does not.
+#
+# resolver: ./custom-snapshot.yaml
+# resolver: https://example.com/snapshots/2018-01-01.yaml
+resolver: lts-11.12
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+# - location:
+#    git: https://github.com/commercialhaskell/stack.git
+#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#  subdirs:
+#  - auto-update
+#  - wai
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver
+# using the same syntax as the packages field.
+# (e.g., acme-missiles-0.3)
+# extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=1.7"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor

test/integration/tests/3959-order-of-flags/files/test/Spec.hs

@@ -0,0 +1,2 @@
+main :: IO ()
+main = putStrLn "Test suite not yet implemented"