[lit] Add test directory to sys.path before invoking it.

[zturner]

Summary

Test suites with complicated configuration logic may wish to split this logic up over multiple packages / modules. This is currently tricky because in order to do import x from the same directory, the directory has to be in sys.path. What I'd really like is to find a way to make the test suite an actual package. It seems that due to the way we compile / exec it, it's still part of the lit.llvm package. (For example, the value of __package__ from within one of these files is 'lit.llvm'. It would be nice if we could detach it from the top-level lit package and make it be its own package. This way from . import foo would "just work".

Anyway, that's for another day, for now this at least allows it to work.

[stella.stamenova]

llvm/utils/lit/lit/TestingConfig.py

109

Won't this always reset the path back to the original path since the finally block always executes?

[zturner]

llvm/utils/lit/lit/TestingConfig.py

109

Yes, but I think that's actually what we want. In fact I think not doing this is a bug that's always been present. i.e. even if we don't append our own path, we should still be doing this. Imagine a case where the code you exec / compile modifies sys.path. Then later we run another test suite, it will have had its sys.path affected by the run of the first test suite. Since sys.path is a module level property, any test suite could affect any other test suite this way.

I don't think any test suites are currently modifying sys.path so this has never been a problem before, but now that we are explicitly modifying it, we definitely don't want test suite B to be affected by test suite A.

llvm/utils/lit/lit/TestingConfig.py

def load_from_path(self, path, litConfig):
             litConfig.fatal('unable to load config file: %r' % (path,))
         f.close()
 
         # Execute the config script to initialize the object.
         cfg_globals = dict(globals())
         cfg_globals['config'] = self
         cfg_globals['lit_config'] = litConfig
         cfg_globals['__file__'] = path
+        original_sys_path = list(sys.path)
         try:
+            # Add the directory name to sys.path.  This way individual
+            # test suites can write "import foo" or "from foo import bar"
+            # so that they can split complex logic up amongst multiple
+            # modules
+            sys.path.append(os.path.dirname(path))
             exec(compile(data, path, 'exec'), cfg_globals, None)
             if litConfig.debug:
                 litConfig.note('... loaded config %r' % path)
         except SystemExit:
             e = sys.exc_info()[1]
             # We allow normal system exit inside a config file to just
             # return control without error.
             if e.args:
                 raise
         except:
             import traceback
             litConfig.fatal(
                 'unable to parse config file %r, traceback: %s' % (
                     path, traceback.format_exc()))
-
+        finally:
+            sys.path = original_sys_path
         self.finish(litConfig)
 
     def __init__(self, parent, name, suffixes, test_format,
                  environment, substitutions, unsupported,
                  test_exec_root, test_source_root, excludes,
                  available_features, pipefail, limit_to_features = [],
                  is_early = False, parallelism_group = ""):
         self.parent = parent