test infra cleanup: convert test_runner lib into package

Also does the following:
* adopts PEP8 naming convention for OptionalWith class (now
  optional_with).
* moves test_runner/lldb_utils.py to lldbsuite/support/optional_with.py.
* packages tests in a subpackage of test_runner per recommendations in
  http://the-hitchhikers-guide-to-packaging.readthedocs.org/en/latest/creation.html

Tests can be run from within pacakges/Python/lldbsuite/test via this
command:

  python -m unittest discover test_runner

The primary cleanup this allows is avoiding the need to muck with the
PYTHONPATH variable from within the source files.  This also aids some
of the static code checkers as they don't need to run code to determine
the proper python path.

llvm-svn: 266710

1 files changed, 56 insertions, 0 deletions

diff --git a/lldb/packages/Python/lldbsuite/support/optional_with.py b/lldb/packages/Python/lldbsuite/support/optional_with.py
new file mode 100644
index 00000000000..41342288bc6
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/support/optional_with.py
@@ -0,0 +1,56 @@
+# ====================================================================
+# Provides a with-style resource handler for optionally-None resources
+# ====================================================================
+
+class optional_with(object):
+    # pylint: disable=too-few-public-methods
+    # This is a wrapper - it is not meant to provide any extra methods.
+    """Provides a wrapper for objects supporting "with", allowing None.
+
+    This lets a user use the "with object" syntax for resource usage
+    (e.g. locks) even when the wrapped with object is None.
+
+    e.g.
+
+    wrapped_lock = optional_with(thread.Lock())
+    with wrapped_lock:
+        # Do something while the lock is obtained.
+        pass
+
+    might_be_none = None
+    wrapped_none = optional_with(might_be_none)
+    with wrapped_none:
+        # This code here still works.
+        pass
+
+    This prevents having to write code like this when
+    a lock is optional:
+
+    if lock:
+        lock.acquire()
+
+    try:
+        code_fragment_always_run()
+    finally:
+        if lock:
+            lock.release()
+
+    And I'd posit it is safer, as it becomes impossible to
+    forget the try/finally using optional_with(), since
+    the with syntax can be used.
+    """
+    def __init__(self, wrapped_object):
+        self.wrapped_object = wrapped_object
+
+    def __enter__(self):
+        if self.wrapped_object is not None:
+            return self.wrapped_object.__enter__()
+        else:
+            return self
+
+    def __exit__(self, the_type, value, traceback):
+        if self.wrapped_object is not None:
+            return self.wrapped_object.__exit__(the_type, value, traceback)
+        else:
+            # Don't suppress any exceptions
+            return False