Hadrian: add --test-root-dirs, to only run specific directories of tests

We can specify several of those, by using the flag multiple times or
just once but combining the directories with ':'.

Along the way, this patch also fixes the testsuite-related --only flag,
so that we can use it many times instead of being force to specify a
space-separated list of test in a single --only flag.

3 files changed, 49 insertions, 4 deletions

diff --git a/hadrian/doc/testsuite.md b/hadrian/doc/testsuite.md
index f1164ff39e..a905e8b3bb 100644
--- a/hadrian/doc/testsuite.md
+++ b/hadrian/doc/testsuite.md
@@ -19,6 +19,8 @@ needed by the tests.
 
 ## Running only a subset of the testsuite
 
+### Specific tests
+
 You can use the `TEST` environment variable, like with the
 Make build system, or the `--only=...` command line argument.
 This is best illustrated with examples:
@@ -40,6 +42,35 @@ TEST="test1 test2" build test
 TEST="test1 test2" build test --only="test3 test4"
 ```
 
+### Whole directories of tests
+
+You can also ask Hadrian to run all the tests that live under one or
+more directories, under which the testsuite driver will be looking for
+`.T` files (usually called `all.T`), where our tests are declared.
+
+By default, the `test` rule tries to run all the tests available (the ones
+under `testsuite/tests/` as well as all the tests of the boot libraries
+or programs (`base`, `haddock`, etc).
+
+To restrict the testsuite driver to only run a specific directory of tests,
+e.g `testsuite/tests/th`, you can simply do:
+
+``` sh
+$ build -j test --test-root-dirs=testsuite/tests/th
+```
+
+If you want to run several directories of tests, you can either
+use several `--test-root-dirs` arguments or just one but separating
+the various directories with `:`:
+
+``` sh
+# first approach
+build -j test --test-root-dirs=testsuite/tests/th --test-root-dirs=testsuite/tests/gadt
+
+# second approach
+build -j test --test-root-dirs=testsuite/tests/th:testsuite/tests/gadt
+```
+
 ## Accepting new output
 
 You can use the `-a` or `--test-accept` flag to "accept" the new
diff --git a/hadrian/src/CommandLine.hs b/hadrian/src/CommandLine.hs
index 37d6607a24..41b2f8d0b9 100644
--- a/hadrian/src/CommandLine.hs
+++ b/hadrian/src/CommandLine.hs
@@ -53,6 +53,7 @@ data TestArgs = TestArgs
     , testOnly       :: [String]
     , testOnlyPerf   :: Bool
     , testSkipPerf   :: Bool
+    , testRootDirs   :: [FilePath]
     , testSpeed      :: TestSpeed
     , testSummary    :: Maybe FilePath
     , testVerbosity  :: Maybe String
@@ -71,6 +72,7 @@ defaultTestArgs = TestArgs
     , testOnly       = []
     , testOnlyPerf   = False
     , testSkipPerf   = False
+    , testRootDirs   = []
     , testSpeed      = TestNormal
     , testSummary    = Nothing
     , testVerbosity  = Nothing
@@ -153,9 +155,10 @@ readTestJUnit filepath = Right $ \flags -> flags { testArgs = (testArgs flags) {
 
 readTestOnly :: Maybe String -> Either String (CommandLineArgs -> CommandLineArgs)
 readTestOnly tests = Right $ \flags ->
-  flags { testArgs = (testArgs flags) { testOnly = tests' } }
+  flags { testArgs = (testArgs flags) { testOnly = tests'' flags } }
 
   where tests' = maybe [] words tests
+        tests'' flags = testOnly (testArgs flags) ++ tests'
 
 readTestOnlyPerf :: Either String (CommandLineArgs -> CommandLineArgs)
 readTestOnlyPerf = Right $ \flags -> flags { testArgs = (testArgs flags) { testOnlyPerf = True } }
@@ -163,6 +166,13 @@ readTestOnlyPerf = Right $ \flags -> flags { testArgs = (testArgs flags) { testO
 readTestSkipPerf :: Either String (CommandLineArgs -> CommandLineArgs)
 readTestSkipPerf = Right $ \flags -> flags { testArgs = (testArgs flags) { testSkipPerf = True } }
 
+readTestRootDirs :: Maybe String -> Either String (CommandLineArgs -> CommandLineArgs)
+readTestRootDirs rootdirs = Right $ \flags ->
+  flags { testArgs = (testArgs flags) { testRootDirs = rootdirs'' flags } }
+
+  where rootdirs' = maybe [] (splitOn ":") rootdirs
+        rootdirs'' flags = testRootDirs (testArgs flags) ++ rootdirs'
+
 readTestSpeed :: Maybe String -> Either String (CommandLineArgs -> CommandLineArgs)
 readTestSpeed ms =
     maybe (Left "Cannot parse test-speed") (Right . set) (go =<< lower <$> ms)
@@ -243,6 +253,8 @@ optDescrs =
       "Only run performance tests."
     , Option [] ["skip-perf"] (NoArg readTestSkipPerf)
       "Skip performance tests."
+    , Option [] ["test-root-dirs"] (OptArg readTestRootDirs "DIR1:[DIR2:...:DIRn]")
+      "Test root directories to look at (all by default)."
     , Option [] ["test-speed"] (OptArg readTestSpeed "SPEED")
       "fast, slow or normal. Normal by default"
     , Option [] ["summary"] (OptArg readTestSummary "TEST_SUMMARY")
diff --git a/hadrian/src/Settings/Builders/RunTest.hs b/hadrian/src/Settings/Builders/RunTest.hs
index 21796478a7..6cc11f8aef 100644
--- a/hadrian/src/Settings/Builders/RunTest.hs
+++ b/hadrian/src/Settings/Builders/RunTest.hs
@@ -86,7 +86,10 @@ runTestBuilderArgs = builder RunTest ? do
     top         <- expr $ topDirectory
     ghcFlags    <- expr runTestGhcFlags
     timeoutProg <- expr buildRoot <&> (-/- timeoutPath)
-
+    cmdrootdirs <- expr (testRootDirs <$> userSetting defaultTestArgs)
+    let defaultRootdirs = ("testsuite" -/- "tests") : libTests
+        rootdirs | null cmdrootdirs = defaultRootdirs
+                 | otherwise        = cmdrootdirs
     -- See #16087
     let ghcBuiltByLlvm = False -- TODO: Implement this check
 
@@ -94,8 +97,7 @@ runTestBuilderArgs = builder RunTest ? do
 
     -- TODO: set CABAL_MINIMAL_BUILD/CABAL_PLUGIN_BUILD
     mconcat [ arg $ "testsuite/driver/runtests.py"
-            , arg $ "--rootdir=" ++ ("testsuite" -/- "tests")
-            , pure ["--rootdir=" ++ test | test <- libTests]
+            , pure [ "--rootdir=" ++ testdir | testdir <- rootdirs ]
             , arg "-e", arg $ "windows=" ++ show windows
             , arg "-e", arg $ "darwin=" ++ show darwin
             , arg "-e", arg $ "config.local=False"