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open-policy-agent
is_number does not correctly return false (also the other is_ type checking builtins)
Short description
% opa eval 'is_number("foo")'
{}
Steps To Reproduce
Expected behavior
Should return false according to docs and according to design. https://www.openpolicyagent.org/docs/latest/policy-reference/#builtin-types-is_number
Additional context
% opa version
Version: 0.42.2
Build Commit: efcf506
Build Timestamp: 2022-07-13T08:28:33Z
Build Hostname: Mac-1657700812705.local
Go Version: go1.18.3
Platform: darwin/amd64
WebAssembly: available
Seems to affect the other type checking builtins too. Because they are all affected, there may be a thought to simply adopt the current behavior as THE CORRECT behavior. But the current behavior has some serious downsides such as:
- these type checking builtins are inconsistent with all the other
is_builtins in Rego which return false (at least according to docs) and lead to confusion/frustration. - confusing and very inconvenient behavior when we want to pass the result of
is_number(x)as an argument into another function call.
Some of this could be worked around with helper methods...
import future.keywords
number_(x) if is_number(x)
number_(x) := false if not is_number(x)
x := number_("foo")
y := number_(2)
We just recently made this exact change for the various x.is_valid functions, so having the same behavior here would be consistent with that. Unless there's a strong reason to treat is_number differently than those, I think we should make the same change here.
Looking at the policy reference for is_number I'm reminded that there's a whole bunch of other is_x functions too. If we do change something here it should probably not be isolated to is_number then.
From the Policy Reference page this is the precise list of is_type functions that we need to worry about:
