[New-bugs-announce] [issue37196] Allowing arbitrary expressions in the @expression syntax

[Géry]

New submission from Géry <gery.ogam at gmail.com>:

Could we allow arbitrary expressions in the @expression syntax for applying decorators to functions/classes? The current grammar restriction to:

    decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE

is very surprising and I don't understand the real motivation.

I find it weird that you are not able to do that:

    def f():
        def g():
            def h(x):
                pass
            return h
        return g
    
    @f()()
    def i():
        pass

since you get:

        @f()()
            ^
    SyntaxError: invalid syntax

but the following is perfectly valid:

    def f():
        def g():
            def h(x):
                pass
            return h
        return g
    
    def g(x):
        def h(x):
            pass
        return g
    
    @g(f()())
    def h():
        pass

See this post for more details: https://stackoverflow.com/questions/56490579

----------
components: Interpreter Core
messages: 344939
nosy: bob.ippolito, exarkun, gvanrossum, j1m, maggyero, mwh, rhettinger
priority: normal
severity: normal
status: open
title: Allowing arbitrary expressions in the @expression syntax
type: enhancement
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue37196>
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