fix!: use stable key ordering for snapshots with maps

[jamestelfer]

Snapshots containing maps are unstable because iteration order of a map's keys is not guaranteed. This leads to test instability, where instability increases with the size of the map included in the snapshot.

Stability can be introduced by using the option of the go-spew library that sorts map keys before serialization (the SortKeys option). The SortKeys option only deals with keys that are native types, or types that implement Stringer or error, but this covers a significant proportion of the uses of map.

Breaking change: This change turns the SortKeys option on for all snapshots, potentially invalidating snapshots that already exist. In reality though, given the instability of maps in snapshots currently, it's unlikely any user of the library will be affected.

Further development

There is another option: SpewKeys. This extends the function of SortKeys to other types by first using go-spew to serialize the type to a string. In my opinion, this is likely to either be (a) something a library user might want to opt into, and (b) a less-likely scenario. For this reason, I've left that option as a potential future development.

See also

• go-spew configuration reference.

[codecov]

Codecov Report

Base: 87.02% // Head: 87.04% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (7496539) compared to base (0854b36).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #190      +/-   ##
==========================================
+ Coverage   87.02%   87.04%   +0.01%     
==========================================
  Files          10       10              
  Lines         740      741       +1     
==========================================
+ Hits          644      645       +1     
  Misses         58       58              
  Partials       38       38              

Impacted Files	Coverage Δ
snapshot.go	84.00% <100.00%> (+0.21%)	⬆️

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[MarvinJWendt]

LGTM! Thanks for contributing! 🚀

There is another option: SpewKeys. This extends the function of SortKeys to other types by first using go-spew to serialize the type to a string.

Sounds interesting, but I agree that this should probably be opt-in.