PragTob
Deep_merge 0.1.0 - deep merging maps, keyword lists + more
Hey everyone, I created and published a new library to deep merge maps and keyword lists. You can find it on github, hex and hexdocs. I also wrote a small release blog post detailing how the library came to be after trying to get deep_merge into elixir.
Library usage is easy as expected:
DeepMerge.deep_merge(%{a: 1, b: [x: 10, y: 9]}, %{b: [y: 20, z: 30], c: 4})
# => %{a: 1, b: [x: 10, y: 20, z: 30], c: 4}
More features include:
- It handles both maps and keyword lists
- It does not merge structs or maps with structs…
- …but you can implement the simple
DeepMerge.Resolverprotocol for types/structs of your choice to also make them be deep mergable - a deep_merge/3 variant that gets a function similar to Map.merge/3 to modify the merging behavior, for instance in case you don’t want keyword lists to be merged or you want all lists to be appended
Feedback, comments and others all welcome 
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PragTob
As José said you’ll find the reasons there, I described the story in the release blog post - it started with a proposal on elixir-core.
Mainly concerns were about how often it’d be useful, that the right implementation would probably be protocols and that it’d be a bit overkill to add a protocol to the language for a feature with questioned general utilization.
It might be my interpretation, but there seems to be a chance that something like deep_merge will be added to Elixir at some time in the future if it turns out to be more useful/popular/something:
I believe though there are still too many questions to be answered before moving forward.
and
(..) as long as you pick a sane namespace, like DeepMerge, it should be fine. It is unlikely we would add it to Elixir as DeepMerge.
All that said, I think a library is a perfectly fine place for this to live, thanks to hex it’s easy to add and use and I hope the library lives up to all your quality standards and if not please tell me
Plus, I have to commend the elixir team for rejecting features. Imo it’s a hard but very necessary thing to do to keep a project lean and maintainable 
PragTob
Resurrection time 
I just released 1.0.0 as the API has been proven stable, added some small goodies to go with it.
I consider it feature completely, so save good feature ideas, bugs, performance improvements, compiler warnings it shouldn’t see any more updates.
Enjoy deep merging
josevalim
See [Proposal] Implement Map.deep_merge/2 and Map.deep_merge/3 by PragTob · Pull Request #5339 · elixir-lang/elixir · GitHub for a discussion on why it is not part of core.
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