Open jgalliers opened 8 months ago
Hi, assuming the searchBudget
is the cause, we can adjust the value a little but not remove it. The search budget is necessary to keep the diffing algorithm as O(N), while the theoretical optimal diffing algorithm is O(N^2).
Assuming your repro is representative of what you usually do, then we could probably remove the searchBudget
constraint if N is below a certain number since N^2 is still not that big if N is small.
I am using cmp.Diff() with a reporter to manage some complex tests. The library is excellent but I have encountered confusing behaviour which also seems to be undocumented, unless I have missed it.
When a large portion of a slice struct changes, the slice is reported as an entirely new object. From what I can tell this happens when more than half of the properties change.
I cannot find this behaviour documented anywhere except a passing reference (possibly?) in the searchBudget variable .
https://github.com/google/go-cmp/blob/c3ad8435e7bef96af35732bc0789e5a2278c6d5f/cmp/internal/diff/diff.go#L185-L188
My tests assume that when I change a property of an object with 6 properties, I receive the associated diff, rather than arbitrarily seeing (for example) 3 changes, and then "a new object" when 4 changes are present.
I appreciate this may be unique to me but it caught me by surprise and took a considerable amount of time to troubleshoot.
I have posted a minimum reproducible example here - https://github.com/jgalliers/go-cmp-repro
go run .
will show a diff with 3 changes followed by changing a property (bringing the total changes to 4) which converts the diff output to a single change, which is an entirely new object.3 diffs:
4 diffs:
Is this desired or expected behaviour? Is it possible to disable this behaviour?
I would vastly prefer to receive a full property-wise diff, each property of which is reportable via the vx/vy objects rather than suddenly receiving a vy object with
IsValid() = false
due to the sudden conversion to a null pointer.