Use Tasty as the test runner in the OSS build

This gives us
* Parallel test runs
* Test listing via `--list-tests`
* Test selection via `-p <pattern>`

Author: simonmar

.github/workflows/ci.yml

@@ -172,7 +172,7 @@ jobs:
         run: make glean-hie
 
       - name: Run tests
-        run: make test
+        run: TASTY_NUM_THREADS=32 make test
 
   # check the vscode extension builds
   vscode:

glean.cabal.in

@@ -230,7 +230,9 @@ library stubs
         glean:if-glean-hs,
         glean:if-index-hs,
         mangle,
-        template-haskell
+        template-haskell,
+        tasty,
+        tasty-hunit-adapter
 
 library logger
     import: fb-haskell, fb-cpp, deps
@@ -2236,6 +2238,9 @@ test-suite glean-snapshot-hack
     if !flag(hack-tests)
         buildable: False
 
+-- The Haskell indexer tests *only* work when run using Cabal with
+-- `cabal run` or `cabal test`, because Cabal puts the `hie-indexer`
+-- binary in the PATH.
 test-suite glean-snapshot-haskell
     import: fb-haskell, fb-cpp, deps, exe, haskell-indexer
     hs-source-dirs: glean/lang/haskell/tests

glean/github/TestRunner.hs

@@ -8,16 +8,36 @@
 
 module TestRunner (module TestRunner) where
 
-import Control.Monad
-import System.Exit
+import System.Environment (withArgs)
 import Test.HUnit
+import qualified Test.Tasty as Tasty
+import qualified Test.Tasty.HUnit.Adapter as Tasty
 
+-- | Wraps the HUnit test using tasty, so we get parallel test runs,
+-- test listing, and test selection.
 testRunner :: Test -> IO ()
-testRunner t = do
-  Counts{..} <- runTestTT t
-  when (errors + failures > 0) $ exitWith (ExitFailure 1)
+testRunner t =
+  Tasty.defaultMain $
+  Tasty.testGroup "test" $
+  Tasty.hUnitTestToTestTree t
 
 data TestAction = TestAction
 
+-- | This entry point is designed for combining the test runner's
+-- option parser with the program's own options. Ideally we would use
+-- this to combine Tasty's option parser with the program's parser,
+-- but Tasty's option parser depends on the `Test`, and we don't have
+-- that when parsing options (it might depend on the options), so
+-- there's a circular dependency.
+--
+-- Therefore we run Tasty's CLI parser with empty arguments. We can
+-- still use the environment variables to set Tasty options, e.g.
+--
+-- > TASTY_NUM_THREADS=12 cabal run my-test
+--
 testRunnerAction :: TestAction -> Test -> IO ()
-testRunnerAction _ = testRunner
+testRunnerAction _ t =
+  withArgs [] $
+  Tasty.defaultMain $
+  Tasty.testGroup "test" $
+  Tasty.hUnitTestToTestTree t