• Kirill Smelkov's avatar
    golang: Fix `@func(cls) def name` not to set `name` in calling context · 30f06b4a
    Kirill Smelkov authored
    This is take 2 after 924a808c (golang: Fix `@func(cls) def name` not to
    override `name` in calling context). There we fixed it not to override
    name if name was already set, but for the case of unset name it was
    still set. The following example was thus not working correctly as
    builtin `next` was shadowed:
    
        class BitSync
    
        @func(BitSync)
        def next(): ...         # this was shadowing access to builtin next
    
        def peek(seq):
            return next(...)    # here next was taken not from builtin, but
                                # from result of above shadowing
    
    To solve the problem in the patch from 2019 I initially contemplated
    patching bytecode because python unconditionally does STORE_NAME after a
    function is defined with decorator:
    
        In [2]: c = """
           ...: @fff
           ...: def ccc():
           ...:     return 1
           ...: """
    
        In [3]: cc = compile(c, "file", "exec")
    
        In [4]: dis(cc)
          2           0 LOAD_NAME                0 (fff)
                      3 LOAD_CONST               0 (<code object ccc at 0x7fafe58d0130, file "file", line 2>)
                      6 MAKE_FUNCTION            0
                      9 CALL_FUNCTION            1
                     12 STORE_NAME               1 (ccc)	<-- NOTE means: ccc = what fff() call returns
                     15 LOAD_CONST               1 (None)
                     18 RETURN_VALUE
    
    However after hitting this problem for real again and taking a fresh
    look I found a way to arrange for the good end result without bytecode
    magic: if name is initially unset @func can install its own custom
    object, which, when overwritten by normal python codeflow of invoking
    STORE_NAME after decorator, unsets the attribute.
    
    That works quite ok and the patch with the fix is small.
    
    /cc @jerome
    /proposed-for-review-on nexedi/pygolang!28
    30f06b4a
golang_test.py 54.1 KB