[lldb/test] Use @skipIfWindows for PExpectTest

[rupprecht]

Summary

Annotating PExpectTest with @skipIfWindows instead of marking it as an empty class will make the test runner recognize it as a test class, which should allow me to reland adb5c23f8c0d60eeec41dcbe21d1b26184e1c97d.

I don't have a windows machine to verify this works, but I did some tests using @skipIfLinux and they all worked as expected. In case the pexpect import is not at all available on windows, I moved it to within the method where it's used.

[labath]

This looks like it could work, though only barely. @skipIfWindows checks for target system, but we would really need this to check the host OS (for remote testing, although I don't know if anyone does that on windows these days). However, in conjuction with @skipIfRemote it should do the right thing. In any case, this is small enough a change to try it out. Just be sure to check the windows bot afterwards.

lldb/packages/Python/lldbsuite/test/lldbpexpect.py

 from __future__ import absolute_import
 
 # System modules
 import os
 import sys
 
 # Third-party modules
 import six
 
 # LLDB Modules
 import lldb
 from .lldbtest import *
 from . import lldbutil
 from lldbsuite.test.decorators import *
 
-if sys.platform.startswith('win32'):
-    # llvm.org/pr22274: need a pexpect replacement for windows
-    class PExpectTest(object):
-        pass
-else:
-    import pexpect
-
-    @skipIfRemote
-    class PExpectTest(TestBase):
+@skipIfWindows  # llvm.org/pr22274: need a pexpect replacement for windows
 
-        NO_DEBUG_INFO_TESTCASE = True
-        PROMPT = "(lldb) "
 
-        def expect_prompt(self):
-            self.child.expect_exact(self.PROMPT)
 
-        def launch(self, executable=None, extra_args=None, timeout=30, dimensions=None):
-            logfile = getattr(sys.stdout, 'buffer',
-                              sys.stdout) if self.TraceOn() else None
 
-            args = ['--no-lldbinit', '--no-use-colors']
-            for cmd in self.setUpCommands():
-                args += ['-O', cmd]
-            if executable is not None:
-                args += ['--file', executable]
-            if extra_args is not None:
-                args.extend(extra_args)
 
-            env = dict(os.environ)
-            env["TERM"]="vt100"
 
-            self.child = pexpect.spawn(
-                    lldbtest_config.lldbExec, args=args, logfile=logfile,
-                    timeout=timeout, dimensions=dimensions, env=env)
-            self.expect_prompt()
-            for cmd in self.setUpCommands():
-                self.child.expect_exact(cmd)
-                self.expect_prompt()
-            if executable is not None:
-                self.child.expect_exact("target create")
-                self.child.expect_exact("Current executable set to")
-                self.expect_prompt()
+        import pexpect
 
-        def expect(self, cmd, substrs=None):
-            self.assertNotIn('\n', cmd)
-            self.child.sendline(cmd)
-            if substrs is not None:
-                for s in substrs:
-                    self.child.expect_exact(s)
-            self.expect_prompt()
 
-        def quit(self, gracefully=True):
-            self.child.sendeof()
-            self.child.close(force=not gracefully)
-            self.child = None
 
-        def cursor_forward_escape_seq(self, chars_to_move):
-            """
-            Returns the escape sequence to move the cursor forward/right
-            by a certain amount of characters.
-            """
-            return b"\x1b\[" + str(chars_to_move).encode("utf-8") + b"C"