[PATCH RFC 1/7] util: asyncio-related helpers

[John Snow <jsnow@redhat.com>]

Nothing too interesting design-wise here; mostly asyncio-related helpers
designed to make writing Python 3.6-compliant code a little nicer to
read.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 util.py | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 util.py

diff --git a/util.py b/util.py
new file mode 100644
index 0000000..2640f82
--- /dev/null
+++ b/util.py
@@ -0,0 +1,87 @@
+"""
+Misc. utils and helper functions
+"""
+
+import asyncio
+import traceback
+import sys
+from typing import (
+    Any,
+    Coroutine,
+    TypeVar,
+)
+
+
+T = TypeVar('T')
+
+
+def create_task(coro: Coroutine[Any, Any, T]) -> 'asyncio.Future[T]':
+    """
+    Python 3.6-compatible create_task() wrapper.
+    """
+    if hasattr(asyncio, 'create_task'):
+        # Python 3.7+
+        return asyncio.create_task(coro)
+
+    # Python 3.6
+    return asyncio.ensure_future(coro)
+
+
+async def wait_closed(writer: asyncio.StreamWriter) -> None:
+    """
+    Python 3.6-compatible StreamWriter.wait_closed() wrapper.
+    """
+    if hasattr(writer, 'wait_closed'):
+        # Python 3.7+
+        await writer.wait_closed()
+    else:
+        # Python 3.6
+        transport = writer.transport
+        assert isinstance(transport, asyncio.WriteTransport)
+
+        while not transport.is_closing():
+            await asyncio.sleep(0.0)
+        while transport.get_write_buffer_size() > 0:
+            await asyncio.sleep(0.0)
+
+
+def asyncio_run(coro: Coroutine[Any, Any, T]) -> T:
+    """
+    Python 3.6-compatible asyncio.run() wrapper.
+    """
+    # Python 3.7+
+    if hasattr(asyncio, 'run'):
+        return asyncio.run(coro)
+
+    # Python 3.6
+    loop = asyncio.get_event_loop()
+    ret = loop.run_until_complete(coro)
+    loop.close()
+
+    return ret
+
+
+def pretty_traceback() -> str:
+    """
+    Print the current traceback, but indented to provide visual distinction.
+
+    This is useful for printing a traceback within a traceback for
+    debugging purposes when encapsulating errors to deliver them up the
+    stack; when those errors are printed, this helps provide a nice
+    visual grouping to quickly identify the parts of the error that
+    belong to the inner exception.
+
+    :returns: A string, formatted something like the following::
+
+      | Traceback (most recent call last):
+      |   File "foobar.py", line 42, in arbitrary_example
+      |     foo.baz()
+      | ArbitraryError: [Errno 42] Something bad happened!
+
+    """
+    exc_lines = []
+    for chunk in traceback.format_exception(*sys.exc_info()):
+        for line in chunk.split("\n"):
+            if line:
+                exc_lines.append(f"  | {line}")
+    return "\n".join(exc_lines)
-- 
2.30.2