[lit] Support relative path arguments

[GMNGeoffrey]

Summary

Currently the behavior with relative paths is pretty broken. It differs
between external shell and internal shell because the path resolution
is done with a different working directory. With the internal shell,
it's resolved relative to the directory from which lit is executed,
whereas with the external shell it's resolved relative to where the
test case is executed. To make matters worse, using the internal shell
the filepath to binaries looked up with which is returned relative
to the directory from which lit is executed, but then executed from
the test execution directory. That means that relative paths with the
internal shell give a [Errno 2] No such file or directory error
instead of the expected command not found.

To address these issues this patch makes lit interpret relative paths
as relative to the directory from which lit was invoked and modifies
which to return absolute paths, matching the behavior of its
namesake unix function.

See https://groups.google.com/g/llvm-dev/c/KzMWlOXR98Y/m/QJoqn0U5HAAJ

[GMNGeoffrey]

Return absolute paths from which

[GMNGeoffrey]

Pre-merge failures are due to a buildkite outage: https://www.buildkitestatus.com/incidents/5xlht1w0p780

[yln]

I haven't been in a situation where I had to (manually) use this option, but your explanation sounds sensible to me.

LGTM with 1 optional nit!

llvm/utils/lit/lit/cl_arguments.py

241–244

Could we replace this block by specifying type=os.path.abspath as the "converter" function where the --path argument is declared?

[GMNGeoffrey]

Use type=os.path.abspath

[GMNGeoffrey]

llvm/utils/lit/lit/cl_arguments.py

241–244

Indeed we can, thanks!

[GMNGeoffrey]

Rebase on head

[GMNGeoffrey]

The only pre-merge failure is LLVM :: Bindings/Go/go.test which is failing for lots of people, as discussed in https://groups.google.com/g/llvm-dev/c/o07dxO7Y-CA. Going to land past that

llvm/utils/lit/lit/cl_arguments.py

for code in success_codes:
             action="append_const",
             const=code,
             default=[])
 
     execution_group = parser.add_argument_group("Test Execution")
     execution_group.add_argument("--path",
             help="Additional paths to add to testing environment",
             action="append",
-            default=[])
+            default=[],
+            type=os.path.abspath)
     execution_group.add_argument("--vg",
             dest="useValgrind",
             help="Run tests under valgrind",
             action="store_true")
     execution_group.add_argument("--vg-leak",
             dest="valgrindLeakCheck",
             help="Check for memory leaks under valgrind",
             action="store_true")
if opts.numShards or opts.runShard:
         if opts.runShard > opts.numShards:
             parser.error("--run-shard must be between 1 and --num-shards (inclusive)")
         opts.shard = (opts.runShard, opts.numShards)
     else:
         opts.shard = None
 
     opts.reports = filter(None, [opts.output, opts.xunit_xml_output, opts.resultdb_output, opts.time_trace_output])
 
     return opts
 
 
 def _positive_int(arg):
     return _int(arg, 'positive', lambda i: i > 0)
 
 
 def _non_negative_int(arg):
     return _int(arg, 'non-negative', lambda i: i >= 0)
 
 
 def _int(arg, kind, pred):

llvm/utils/lit/lit/util.py

def which(command, paths=None):
     else:
         pathext = ['']
 
     # Search the paths...
     for path in paths.split(os.pathsep):
         for ext in pathext:
             p = os.path.join(path, command + ext)
             if os.path.exists(p) and not os.path.isdir(p):
-                return os.path.normcase(os.path.normpath(p))
+                return os.path.normcase(os.path.abspath(p))
 
     return None
 
 
 def checkToolsPath(dir, tools):
     for tool in tools:
         if not os.path.exists(os.path.join(dir, tool)):
             return False