Proper sniffio support requires Python 3.7

Author: smurfix

docs/source/usage.rst

@@ -195,7 +195,8 @@ call async code from both contexts – they have different semantics, esp.
 concerning cancellation.
 
 If you really need to do this, :meth:`sniffio.current_async_library`
-correctly reports "asyncio" when appropriate.
+correctly reports "asyncio" when appropriate. (This requires Python 3.7
+for :mod:`contextvars` support in :mod:`asyncio`.
 
 .. _cross-calling:
 

tests/interop/test_adapter.py

@@ -4,6 +4,7 @@
 import trio
 import sniffio
 from tests import aiotest
+import sys
 
 
 class SomeThing:
@@ -14,14 +15,16 @@ def __init__(self, loop):
 
     @aio2trio
     async def dly_trio(self):
-        assert sniffio.current_async_library() == "trio"
+        if sys.version_info >= (3, 7):
+            assert sniffio.current_async_library() == "trio"
         await trio.sleep(0.01)
         self.flag |= 2
         return 8
 
     @trio2aio
     async def dly_asyncio(self):
-        assert sniffio.current_async_library() == "asyncio"
+        if sys.version_info >= (3, 7):
+            assert sniffio.current_async_library() == "asyncio"
         await asyncio.sleep(0.01, loop=self.loop)
         self.flag |= 1
         return 4

tests/interop/test_calls.py

@@ -4,6 +4,7 @@
 import sniffio
 from tests import aiotest
 from functools import partial
+import sys
 
 
 class Seen:
@@ -24,7 +25,8 @@ def __init__(self, parent):
     async def __aenter__(self):
         assert self.parent.did_it == 0
         self.parent.did_it = 1
-        assert sniffio.current_async_library() == "trio"
+        if sys.version_info >= (3, 7):
+            assert sniffio.current_async_library() == "trio"
         await trio.sleep(0.01)
         self.parent.did_it = 2
         return self
@@ -42,7 +44,8 @@ def __init__(self, parent, loop):
     async def __aenter__(self):
         assert self.parent.did_it == 0
         self.parent.did_it = 1
-        assert sniffio.current_async_library() == "asyncio"
+        if sys.version_info >= (3, 7):
+            assert sniffio.current_async_library() == "asyncio"
         await asyncio.sleep(0.01, loop=self.loop)
         self.parent.did_it = 2
         return self