hasproperty(Base, ::Symbol) seems to give incorrect results for non-exported names

[DilumAluthge]

  | | |_| | | | (_| |  |  Version 1.9.0-DEV.1423 (2022-09-21)
 _/ |\__'_|_|_|\__'_|  |  Commit 62ac26a4b06 (0 days old master)
|__/                   |

julia> getproperty(Base, :_cat)
_cat (generic function with 9 methods)

julia> hasproperty(Base, :_cat)
false

[JeffBezanson]

I think this was intentional. We wanted propertynames to only list exported names, and hasproperty to be consistent with that.

[DilumAluthge]

Ah. In that case, is there a way that I can tell whether or not getproperty will succeed without actually calling it? Right now, I'm just doing a try-catch.

[mikmoore]

It seems to me that hasproperty should match the behavior of getproperty, as nobody want so rely on try-catch to actually check these things. propertynames has a private argument to determine whether private properties should be returned, but it seems there is no similar option for hasproperty. Even if there were, it would seem that the sensible default would be for hasproperty to include private properties and only restrict itself to public properties by an explicit argument, since it seems that the primary purpose is to avoid invalid getproperty calls.

[DilumAluthge]

Kristoffer suggested using isdefined(Base, :foo) for this, and it seems to work perfectly. That is, in my brief experiments, it seems that isdefined(Base, sym) is true if and only if getproperty(Base, sym) does not throw.

So I'm inclined to close this as resolved.

[vtjnash]

That is much more accurate too. Since something can have a property, but still throw UndefRef on access