Allow csp nodes to be defined in IPython

[ptomecek]

Is your feature request related to a problem? Please describe.
At the moment, you can't define a csp node interactively in ipython (need to be part of an importable script)

Defining the following in IPython (inside of PyCharm)

@csp.node
def f(x: csp.ts[int]) -> csp.ts[int]:
    return x

Throws

OSError: could not get source code

Describe the solution you'd like
Ideally we should be able to define them in ipython, but at the very least, the error message should be a bit more helpful (i.e. explaining that defining nodes interactively is not supported yet)

[timkpaine]

That code works for me without error:

[ptomecek]

So it does (when I run ipython from command line), so it seems like it's an IDE (PyCharm) problem on my end. Will close.

[ogarokpeter]

Hi team!

I have a fresh reproduction of this that happens when running Python from command line. I get the same error as described above.

Python 3.8.10 | packaged by conda-forge | (default, Sep 13 2021, 21:46:58)
[GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import csp
>>> import pandas
>>> from datetime import datetime
>>> @csp.graph
... def foo(x: pandas.DataFrame):
...   pass
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/csp/csp/impl/wiring/graph.py", line 393, in graph
    return _impl(func)
  File "/csp/csp/impl/error_handling.py", line 37, in __exit__
    raise exc_val.with_traceback(new_tb)
OSError: could not get source code
>>>

[timkpaine]

@ogarokpeter That looks like Python REPL, not IPython. Please open a separate issue to improve the error message in a REPL (or if a fix is possible, fix it in REPL). Looks like everything works as expected in IPython.