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Specify interface for LibGit2 abstract types #36452

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Jul 13, 2020
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Specify interface for LibGit2 abstract types #36452

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b609aa4
Specify interface for LibGit2 abstract types
timholy Jun 27, 2020
9b0c038
Explain the getproperty methods
timholy Jul 13, 2020
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36 changes: 36 additions & 0 deletions stdlib/LibGit2/src/types.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -966,11 +966,47 @@ function split_cfg_entry(ce::ConfigEntry)
end

# Abstract object types

"""
AbstractGitObject

`AbstractGitObject`s must obey the following interface:
- `obj.owner`, if present, must be a `Union{Nothing,GitRepo,GitTree}`
- `obj.ptr`, if present, must be a `Union{Ptr{Cvoid},Ptr{SignatureStruct}}`
"""
abstract type AbstractGitObject end

function Base.getproperty(obj::AbstractGitObject, name::Symbol)
# These type-assertions enforce the interface requirements above.
# They assist type-inference in cases where the compiler only knows that it
# has an `AbstractGitObject` without being certain about the concrete type.
# See detailed explanation in https://github.com/JuliaLang/julia/pull/36452.
if name === :owner
return getfield(obj, :owner)::Union{Nothing,GitRepo,GitTree}
elseif name === :ptr
return getfield(obj, :ptr)::Union{Ptr{Cvoid},Ptr{SignatureStruct}}
else
return getfield(obj, name)
end
end
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I think a comment should be added explaining that this helps inference as on its own the function looks redundant


Base.isempty(obj::AbstractGitObject) = (obj.ptr == C_NULL)

# `GitObject`s must obey the following interface:
# - `obj.owner` must be a `GitRepo`
# - `obj.ptr` must be a Ptr{Cvoid}
abstract type GitObject <: AbstractGitObject end

function Base.getproperty(obj::GitObject, name::Symbol)
if name === :owner
return getfield(obj, :owner)::GitRepo
elseif name === :ptr
return getfield(obj, :ptr)::Ptr{Cvoid}
else
return getfield(obj, name)
end
end

for (typ, owntyp, sup, cname) in [
(:GitRepo, nothing, :AbstractGitObject, :git_repository),
(:GitConfig, :(Union{GitRepo, Nothing}), :AbstractGitObject, :git_config),
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