[lit] Add back LitTestCase

[yln]

Summary

This essentially reverts a commit [1] that removed the adaptor for
Python unittests. The code has been slightly refactored to make it more
additive: all code is contained in LitTestCase.py.

Usage sites will require a small adaption:

[old]
  import lit.discovery
  ...
  test_suite = lit.discovery.load_test_suite(...)

[new]
  import lit.LitTestCase
  ...
  test_suite = lit.LitTestCase.load_test_suite(...)

This was put back on request by Daniel Dunbar, since I wrongly assumed
that the functionality is unused. At least llbuild still uses this [2].

[1] 70ca752ccf6a8f362aea25ccd3ee2bbceca93b20
[2] https://github.com/apple/swift-llbuild/blob/master/utils/Xcode/LitXCTestAdaptor/LitTests.py#L16

[• vlm]

Thank you! https://github.com/apple/swift-llbuild/pull/588

llvm/utils/lit/lit/LitTestCase.py

+import unittest
+
+import lit.worker
+import lit.LitConfig
+
+"""
+TestCase adaptor for providing a Python 'unittest' compatible interface to 'lit'
+tests.
+"""
+
+
+class UnresolvedError(RuntimeError):
+    pass
+
+
+class LitTestCase(unittest.TestCase):
+    def __init__(self, test, lit_config):
+        unittest.TestCase.__init__(self)
+        self._test = test
+        self._lit_config = lit_config
+
+    def id(self):
+        return self._test.getFullName()
+
+    def shortDescription(self):
+        return self._test.getFullName()
+
+    def runTest(self):
+        # Run the test.
+        lit.worker._execute_test(self._test, self._lit_config)
+
+        # Adapt the result to unittest.
+        result = self._test.result
+        if result.code is lit.Test.UNRESOLVED:
+            raise UnresolvedError(result.output)
+        elif result.code.isFailure:
+            self.fail(result.output)
+
+
+def load_test_suite(inputs):
+    import platform
+    windows = platform.system() == 'Windows'
+
+    # Create the global config object.
+    lit_config = lit.LitConfig.LitConfig(
+        progname='lit',
+        path=[],
+        quiet=False,
+        useValgrind=False,
+        valgrindLeakCheck=False,
+        valgrindArgs=[],
+        noExecute=False,
+        debug=False,
+        isWindows=windows,
+        params={})
+
+    # Perform test discovery.
+    tests = lit.discovery.find_tests_for_inputs(lit_config, inputs)
+    test_adaptors = [LitTestCase(t, lit_config) for t in tests]
+
+    # Return a unittest test suite which just runs the tests in order.
+    return unittest.TestSuite(test_adaptors)

llvm/utils/lit/tests/Inputs/unittest-adaptor/lit.cfg

+import lit.formats
+config.name = 'unittest-adaptor'
+config.suffixes = ['.txt']
+config.test_format = lit.formats.ShTest()
+config.test_source_root = None
+config.test_exec_root = None

llvm/utils/lit/tests/Inputs/unittest-adaptor/test-one.txt

+# RUN: true

llvm/utils/lit/tests/Inputs/unittest-adaptor/test-two.txt

+# RUN: false

llvm/utils/lit/tests/unittest-adaptor.py

+# Check the lit adaption to run under unittest.
+#
+# RUN: %{python} %s %{inputs}/unittest-adaptor 2> %t.err
+# RUN: FileCheck < %t.err %s
+#
+# CHECK-DAG: unittest-adaptor :: test-two.txt ... FAIL
+# CHECK-DAG: unittest-adaptor :: test-one.txt ... ok
+
+import sys
+import unittest
+
+import lit.LitTestCase
+
+input_path = sys.argv[1]
+unittest_suite = lit.LitTestCase.load_test_suite([input_path])
+runner = unittest.TextTestRunner(verbosity=2)
+runner.run(unittest_suite)