[Chore] Update development setup

Problem:

1. Running `nix develop` in the project root does not provide a
   development environment of any sort, as evidenced by:
       ghc-pkg list
   printing only boot libraries.

2. Tests can fail with this error:
       xrefcheck-tests: Network.Socket.bind: resource busy (Address already in use)
   due to a potential conflict with an already running application.

Solution:

1. flake.nix: inherit devShells
2. tests: configurable mock server port

With these changes I've been able to build the project and run its tests
as follows:

    nix shell nixpkgs#haskellPackages.hpack nixpkgs#cabal-install
    nix develop -c $SHELL
    hpack
    vsftpd \
       -orun_as_launching_user=yes \
       -olisten_port=2221 \
       -olisten=yes \
       -oftp_username=$(whoami) \
       -oanon_root=./ftp-tests/ftp_root \
       -opasv_min_port=2222 \
       -ohide_file='{.*}' \
       -odeny_file='{.*}' \
       -oseccomp_sandbox=no \
       -olog_ftp_protocol=yes \
       -oxferlog_enable=yes \
       -ovsftpd_log_file=./ftp.log &
    cabal test ftp-tests --test-options="--ftp-host ftp://127.0.0.1:2221"
    cabal test xrefcheck-tests --test-options="--mock-server-port 3001"

flake.nix

@@ -62,7 +62,7 @@
 
     in
       pkgs.lib.lists.foldr pkgs.lib.recursiveUpdate {} [
-        { inherit (flake) packages apps; }
+        { inherit (flake) packages apps devShells; }
         {
           legacyPackages = pkgs;
 

ftp-tests/Test/Xrefcheck/FtpLinks.hs

@@ -9,7 +9,7 @@ module Test.Xrefcheck.FtpLinks
 
 import Universum
 
-import Data.Tagged (Tagged, untag)
+import Data.Tagged (untag)
 import Options.Applicative (help, long, strOption)
 import Test.Tasty (TestTree, askOption, testGroup)
 import Test.Tasty.HUnit (assertBool, assertFailure, testCase, (@?=))
@@ -36,8 +36,8 @@ instance IsOption FtpHostOpt where
   optionHelp = "[Test.Xrefcheck.FtpLinks] FTP host without trailing slash"
   parseValue v = FtpHostOpt <$> safeRead v
   optionCLParser = FtpHostOpt <$> strOption
-    (  long (untag (optionName :: Tagged FtpHostOpt String))
-    <> help (untag (optionHelp :: Tagged FtpHostOpt String))
+    (  long (untag @FtpHostOpt optionName)
+    <> help (untag @FtpHostOpt optionHelp)
     )
 
 config :: Config

package.yaml

@@ -142,6 +142,8 @@ tests:
     generated-other-modules:
       - Paths_xrefcheck
     dependencies:
+      - optparse-applicative
+      - tagged
       - case-insensitive
       - cmark-gfm
       - containers

tests/Main.hs

@@ -9,7 +9,12 @@ module Main
 import Universum
 
 import Test.Tasty
+import Test.Tasty.Ingredients (Ingredient)
+import Test.Xrefcheck.Util (mockServerOptions)
 import Tree (tests)
 
 main :: IO ()
-main = tests >>= defaultMain
+main = tests >>= defaultMainWithIngredients ingredients
+
+ingredients :: [Ingredient]
+ingredients = includingOptions mockServerOptions : defaultIngredients

tests/Test/Xrefcheck/ConfigSpec.hs

@@ -13,7 +13,7 @@ import Control.Exception qualified as E
 import Data.List (isInfixOf)
 import Data.Yaml (ParseException (..), decodeEither')
 import Network.HTTP.Types (Status (..))
-import Test.Tasty (TestTree, testGroup)
+import Test.Tasty (TestTree, askOption, testGroup)
 import Test.Tasty.HUnit (assertFailure, testCase, (@?=))
 import Test.Tasty.QuickCheck (ioProperty, testProperty)
 
@@ -22,7 +22,7 @@ import Xrefcheck.Core (Flavor (GitHub), allFlavors)
 import Xrefcheck.Scan (ecIgnoreExternalRefsToL)
 import Xrefcheck.Verify (VerifyError (..), checkExternalResource)
 
-import Test.Xrefcheck.Util (mockServer)
+import Test.Xrefcheck.Util (mockServer, mockServerUrl)
 
 test_config :: [TestTree]
 test_config =
@@ -43,28 +43,29 @@ test_config =
             , "and verify changes"
             ]
       ]
-  , testGroup "`ignoreAuthFailures` working as expected" $
+  , askOption $ \mockServerPort ->
+    testGroup "`ignoreAuthFailures` working as expected" $
     let config = defConfig GitHub & cExclusionsL . ecIgnoreExternalRefsToL .~ []
 
         setIgnoreAuthFailures value =
           config & cNetworkingL . ncIgnoreAuthFailuresL .~ value
     in [ testCase "when True - assume 401 status is valid" $
-          checkLinkWithServer (setIgnoreAuthFailures True)
-            "http://127.0.0.1:3000/401" $ Right ()
+          checkLinkWithServer mockServerPort (setIgnoreAuthFailures True)
+            "/401" $ Right ()
 
        , testCase "when False - assume 401 status is invalid" $
-          checkLinkWithServer (setIgnoreAuthFailures False)
-            "http://127.0.0.1:3000/401" $
+          checkLinkWithServer mockServerPort (setIgnoreAuthFailures False)
+            "/401" $
                 Left $ ExternalHttpResourceUnavailable $
                   Status { statusCode = 401, statusMessage = "Unauthorized" }
 
        , testCase "when True - assume 403 status is valid" $
-          checkLinkWithServer (setIgnoreAuthFailures True)
-            "http://127.0.0.1:3000/403" $ Right ()
+          checkLinkWithServer mockServerPort (setIgnoreAuthFailures True)
+            "/403" $ Right ()
 
        , testCase "when False - assume 403 status is invalid" $
-          checkLinkWithServer (setIgnoreAuthFailures False)
-            "http://127.0.0.1:3000/403" $
+          checkLinkWithServer mockServerPort (setIgnoreAuthFailures False)
+            "/403" $
                 Left $ ExternalHttpResourceUnavailable $
                   Status { statusCode = 403, statusMessage = "Forbidden" }
        ]
@@ -80,7 +81,8 @@ test_config =
   ]
 
   where
-    checkLinkWithServer config link expectation =
-      E.bracket (forkIO mockServer) killThread $ \_ -> do
-        result <- runExceptT $ checkExternalResource emptyChain config link
+    checkLinkWithServer mockServerPort config link expectation =
+      E.bracket (forkIO (mockServer mockServerPort)) killThread $ \_ -> do
+        let url = mockServerUrl mockServerPort link
+        result <- runExceptT $ checkExternalResource emptyChain config url
         result @?= expectation

tests/Test/Xrefcheck/Util.hs

@@ -7,7 +7,10 @@ module Test.Xrefcheck.Util where
 
 import Universum
 
+import Data.Tagged (untag)
 import Network.HTTP.Types (forbidden403, unauthorized401)
+import Options.Applicative (auto, help, long, option)
+import Test.Tasty.Options as Tasty (IsOption (..), OptionDescription (Option), safeRead)
 import Web.Firefly (ToResponse (..), route, run)
 
 import Xrefcheck.Core (Flavor)
@@ -18,7 +21,30 @@ parse :: Flavor -> ScanAction
 parse fl path =
   markdownScanner MarkdownConfig { mcFlavor = fl } path
 
-mockServer :: IO ()
-mockServer = run 3000 $ do
+mockServerUrl :: MockServerPort -> Text -> Text
+mockServerUrl (MockServerPort port) s = toText ("http://127.0.0.1:" <> show port <> s)
+
+mockServer :: MockServerPort -> IO ()
+mockServer (MockServerPort port) = run port $ do
   route "/401" $ pure $ toResponse ("" :: Text, unauthorized401)
   route "/403" $ pure $ toResponse ("" :: Text, forbidden403)
+
+-- | All options needed to configure the mock server.
+mockServerOptions :: [OptionDescription]
+mockServerOptions =
+  [ Tasty.Option (Proxy @MockServerPort)
+  ]
+
+-- | Option specifying FTP host.
+newtype MockServerPort = MockServerPort Int
+  deriving stock (Show, Eq)
+
+instance IsOption MockServerPort where
+  defaultValue = MockServerPort 3000
+  optionName = "mock-server-port"
+  optionHelp = "[Test.Xrefcheck.Util] Mock server port"
+  parseValue v = MockServerPort <$> safeRead v
+  optionCLParser = MockServerPort <$> option auto
+    (  long (untag @MockServerPort optionName)
+    <> help (untag @MockServerPort optionHelp)
+    )