old nodes import the parser module (deprecated)

[zeffii]

what to do.. replace with ast.parse() ?

[Durman]

If we'd know for sure that it does not change its behavior it's worth to replace.
If it does change, it can break layouts and users wont be able to understand the cause of it.

In the last case probably it would be better to remove the node implementation and show the message that, for example, Sverchok 1.0 was the last version where the node was supported. And we can wait till the deprecated module will be removed before doing this.

[zeffii]

in py3.10 parser is gone from standard libs. It is not a big deal, the nodes don't use the module extensively..

in essence they use these features:

string_formula = 'x*n[0]'
x = 10
n = [20, 30]

we use

import parser
code_formula = parser.expr(string_formula).compile()
k = eval(code_formula)

print(k)
# >>> 200

equivalent is

# without parser module
code_formula = compile(string_formula, '<string>', mode='eval')
k = eval(code_formula)

print(k)
# >>> 200

the main difference would be slightly different error messages, but failure to parse would still be failure to parse.

[zeffii]

a replacement could be

try:
    import parser
except:
    from dataclasses import dataclass

    @dataclass
    class Expr(str):
        str_formula: str
        def compile(self):
            # print('use mock')
            return compile(self.str_formula, '<string>', mode='eval')

    parser = lambda: None
    parser.expr = lambda str_formula: Expr(str_formula)

[zeffii]

resolved: #4509