ContextVar not preserved when cell contains `await`

[mvolfik]

See https://gist.github.com/mvolfik/2582939ec00120a04503507214c24105

import contextvars, asyncio
VAR = contextvars.ContextVar("VAR", default="default")

async def produce_result(x):
 return x

async def read_var():
 print("Var:", VAR.get())


# The following is broken

# In[3]:
result = await produce_result("bug fixed yayy")
VAR.set(result)

# In[4]:
await read_var()
# Var: default


# The following works

# In[5]:
result = await produce_result("this worked before")

# In[6]:
VAR.set(result)

# In[7]:
await read_var()
# Var: this worked before

In the working case, await result is stored in a variable, and VAR is set from cell which is fully synchronous (idk ipython internals, but that's what I guess makes the difference). What breaks is setting var from the same cell where we call and await the async function.

I'm using ipykernel==6.2.0. Neither of these cases worked (both outputted 'default') with ipykernel==5.5.0.

Related to ipython issue ipython/ipython#11565, which was fixed by #632

[tbenthompson]

I ran into this same issue today with ipykernel==6.20.2.

[RRRajput]

This is still an issue

[alexbarcelo]

I have ran into this and see no workaround nor any way to solve it.

Has somebody found any alternative for allowing my code to work? I am using code as an external library and it is broken because of this ContextVar variable being lost between cells.

Also, what does anybody know the technical reason behind this limitation? I was trying to debug and pinpoint the origin but I don't know a lot of internals, I assume that ipykernel is creating a task/copying context when the cell contains an await and thus it is breaking the expected code flow but that is a wild assumption that I have not confirmed.