Make it easier to customize pexpect interfaces

[simon-king-jena]

While working on #22452, I found a couple of issues that might be dealt with in a separate ticket.

• The pexpect interfaces and the interface elements inherit from Parent resp. from Element. But they override __repr__, which is bad. So, I change __repr__ into single underscore methods in all interfaces.

• The default implementation of _true_symbol and some others rely on the assumption the self.eval(...) returns a string representation when applied to an integer or bool. But this assumption is violated for Polymake. However, self.get(...) is supposed to return a string representation for everything. I am stating these specifications in the doc and replace eval with get where needed.

• For interface elements, I replace self.parent() by self._check_valid() in a couple of places, since that returns the parent after testing that it is still valid.

• In the string representation of an interface element of a crashed interface, I show the crash message, so that it becomes a bit clearer what has happened.

Component: interfaces

Keywords: pexpect, days84

Author: Simon King

Branch/Commit: 52226e2

Reviewer: Jeroen Demeyer, Vincent Delecroix

Issue created by migration from https://trac.sagemath.org/ticket/22501

[simon-king-jena]

comment:1

There is one more thing. The methods _left_list_delim, _right_func_delim and similar are currently only used to make the string representation of an interface element a bit more similar to Python. However, it is conceivable that they could be used in a nice default implementation of __getitem__ - but I am not sure if such a default implementation would really be of wide use.

[simon-king-jena]

Changed keywords from pexpect to pexpect, days84

[simon-king-jena]

Branch: u/SimonKing/make_it_easier_to_customize_pexpect_interfaces

[simon-king-jena]

Commit: 6580782

[simon-king-jena]

comment:4

The first commit implements and uses _get_primitive. Next, I'll add tests.

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New commits:

6580782

Add ._get_primitive to pexpect interfaces

[sagetrac-git]

Changed commit from 6580782 to 33b53f3

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

33b53f3

Add documentation to _get_primitive

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

d78b239

'Implement string representation by single underscore methods': Apply this mantra to interfaces

[sagetrac-git]

Changed commit from 33b53f3 to d78b239

[simon-king-jena]

comment:7

I have now also sanitised string representation of pexpect elements. "Sanitise" means: There is a default __repr__ method that is not supposed to be overridden, and if anything needs to be overridden then it is the single underscore _repr_. The change mainly consisted how invalid objects are printed.

Since I am not particularly eager to remove the superfluous functions mentioned in the ticket description, I'll let this be "needs review" --- now I have the prerequisites for #22452.

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New commits:

d78b239

'Implement string representation by single underscore methods': Apply this mantra to interfaces