[ExpressionLanguage] Document precedence

[homersimpsons]

Current status

The page https://symfony.com/doc/current/reference/formats/expression_language.html#supported-operators does not document operators precedence.

Objective

Add documentation about operators precedence.

Why?

Today I wanted to check the precedence of some operator in order to update a code, I had an expression that could translate to the following ambiguity:

var_dump(! null === false); // => ((!null) === false) => false
var_dump(! (null === false)); // => true

We can find the precedence in https://github.com/symfony/expression-language/blob/b8ec919a6d3d47fc4e7845c256d164413207bf73/Parser.php#L24

I think that this information should be accessible in the doc directly, but I understand that it won't benefit a lot of users so I'm wondering how it should be presented. Maybe just a collapsible array at the end, or when the precedence is mentioned in:

You must use parentheses because the unary operator not has precedence over the binary operator matches.

[94noni]

A note block could be added and document this internal behavior i think yes 👍🏻

[OskarStark]

I really like this note and we should merge it. However, what about a debug command? We have the same for listener priorities

[homersimpsons]

However, what about a debug command?

I'm not sure to understand, there is no command for symfony's expression language, right?

[OskarStark]

Yes, I would propose to create one

[homersimpsons]

What would be the purpose of such command? How do you see its interface?

[OskarStark]

I would output the list from the docs PR, if we can get the info programmatically

[homersimpsons]

I would output the list from the docs PR, if we can get the info programmatically

Yes we can definitely get it programatically rather easily (minus some formating / arranging).

The repo does not have a dependency on the console component, I'm not exactly sure how to approach this. Another command I can think of would be an easy "debug" command where someone could provide an expression (and possibly variables) and get the result.

[javiereguiluz]

Given that the list of operators is very rarely updated, I'd just handle this manually.