`with` statement fails on tuple-unpacking context managers

Bug Reports
1

Description:
It seems that using a context manager that returns a tuple in __enter__ and unpacking it with as (c1, c2) raises an unhandled runtime error.

Example:

class MyContext:
    def __enter__(self):
        return "a", "b"
    def __exit__(self, exc_type, exc_val, exc_tb):
        pass

with MyContext() as (c1, c2):
    print(c1, c2)

Clone link: Anvil | Login

Expected behavior:
This should work as in regular Python.

Actual behavior:
Skulpt raises an unhandled runtime error:

[An internal error has occurred] - see browser console for more details
TypeError: Cannot read properties of undefined (reading 'v')
    at a.nameop (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1055:497)
    at a.cwith (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1025:412)
    at a.vstmt (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1054:205)
    at a.cbody (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1061:341)
    at a.cmod (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1065:162)
    at Sk.compile (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1066:27)
    at Arguments.<anonymous> (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1071:239)
    at Sk.misceval.chain (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:445:408)
    at Arguments.<anonymous> (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:1071:166)
    at Sk.misceval.chain (https://gqkpoioo2fhlto7m.anvil.app/debug/I6IITLBHAZZL236JAT7JM4EGAZLAYCXJ%3DXR76A4DWGIF4B5XDEB2H3SO6/_/static/runtime/js/lib/skulpt.min.js?sha=a687db4bddb8:445:408)

Work around
Return a single value and unpack in within the context:

with MyContext() as my_context:
    c1, c2 = my_context
    print(c1, c2)
2

Some important context: your code works in the server REPL, but on the client side when I try it, I don’t get an error, but a and b don’t print for me.

3

Thanks for reporting. We’ll get that fixed

4

we’ve fixed this upstream in skulpt, so we’ll let you know when it goes live in anvil

3 Likes