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The problem: Argument names of a memoised function (say, f) can be hijacked by names in the body or enclosing environment of the memoising function (memoise(f)).
Example:
memoise(function(hash) hash)("Am I OK?")
#> [1] "9ec45ba0998d8bc3150c..." (output truncated)
This is not a problem that is likely to be encountered for exotic names, like `_f`. For ordinary syntactic names, like hash or args, the likelihood of a name clash is still very low, but not zero. Nevertheless, it might be worthwhile to reduce this likelihood to zero, as this seems possible with a few small changes to memoise() (and, accordingly, has_cache()).
A solution:
To fix clashes with names in the enclosing environment — invoke such names by explicit reference to bindings in the enclosing environment.
To fix clashes with names assigned in the memoised function body — call the underlying (non-memoised) function f in the calling environment, rather than in the function's execution environment, as currently done.
Implementing 1) amounts to changing `_f` to encl$`_f`, etc., where encl gets parent.env(environment()). Implementing 2) amounts to replacing .init_call in memoise.R with eval.parent(`[[<-`(match.call(), 1L, encl$`_f`)).
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The problem: Argument names of a memoised function (say,
f) can be hijacked by names in the body or enclosing environment of the memoising function (memoise(f)).Example:
This is not a problem that is likely to be encountered for exotic names, like
`_f`. For ordinary syntactic names, likehashorargs, the likelihood of a name clash is still very low, but not zero. Nevertheless, it might be worthwhile to reduce this likelihood to zero, as this seems possible with a few small changes tomemoise()(and, accordingly,has_cache()).A solution:
fin the calling environment, rather than in the function's execution environment, as currently done.Implementing 1) amounts to changing
`_f`toencl$`_f`, etc., whereenclgetsparent.env(environment()). Implementing 2) amounts to replacing.init_callin memoise.R witheval.parent(`[[<-`(match.call(), 1L, encl$`_f`)).I have implement such fixes in commits 018ef0a, 7a46d42, e32fb1b.
memoise()is even a bit simpler, now, becausebquote()'ing is no longer necessary. All existing tests pass, in addition to a test that verifies the absence of name clashes.With such changes, argument names won't be hijacked by internal names:
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