JuliaCollections / JuliaCollections/DataStructures.jl

`DefaultDict` and `haskey`

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requires thought
Dominant language
Julia
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Description

I didn't find a conversation around whether haskey should always return true for DefaultDict.

julia> using DataStructures: DefaultDict

julia> d1 = DefaultDict(0, :A=>1, :B=>2)
DefaultDict{Symbol,Int64,Int64} with 2 entries:
  :A => 1
  :B => 2

julia> haskey(d1, :C)
false

julia> d1[:C]
0

This would make it inconsistent with keys, but consistent with getindex.

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the DefaultDict behavior shown in the issue and review how Julia defines haskey, keys, and getindex for missing keys. Resolve the intended contract for haskey, then verify the decision with cases covering both present and missing keys.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
data
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Quiet
Clarity
Needs clarification
Newbie friendliness
30/100

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