WARNING: using XXX.xxx in module Main conflicts with an existing identifier

New to Julia
1

(I’m using Makie as an example but I think my question is how Julia handle Modules and export.)

When I run the following code in a REPL session, I get

WARNING: using GeometryBasics.Mesh in module Main conflicts with an existing identifier.

using GLMakie
f = Figure()
a = Axis(f[1, 1])
using GeometryBasics

My questions are

  1. Why do I get the warning?
  2. What exactly does it mean?
  3. How do I debug / test / investigate when I get the warning?

What I have done so far

If I comment out Axis(), I don’t get that warning.

using GLMakie
f = Figure()
#a = Axis(f[1, 1])
using GeometryBasics

It seems to me both Makie and GeometryBasics exports Mesh:

:Mesh in names(Makie) #-> true
:Mesh in names(GLMakie) #-> true
:Mesh in names(GeometryBasics) #-> true

But the module Main doesn’t have it:

julia> names(Main)
7-element Vector{Symbol}:
 :Base
 :Core
 :InteractiveUtils
 :Main
 :a
 :ans
 :f

When I use ?, REPL seems to know the identifier Mesh but throw UndefRefError

help?> Mesh
search: Mesh mesh mesh! MeshMeta MeshScatter meshscatter meshscatter! UVMesh uv_mesh GLUVMesh GLUVMesh3D GLUVMesh2D PlainMesh GLPlainMesh GLPlainMesh3D GLPlainMesh2D TriangleMesh AbstractMesh

ERROR: UndefRefError: access to undefined reference
Stacktrace:
 [1] getproperty
   @ ./Base.jl:37 [inlined]
 [2] summarize(io::IOBuffer, TT::Type, binding::Base.Docs.Binding)
   @ REPL ~/julia-1.7.2/share/julia/stdlib/v1.7/REPL/src/docview.jl:286
 [3] summarize(binding::Base.Docs.Binding, sig::Type)
   @ REPL ~/julia-1.7.2/share/julia/stdlib/v1.7/REPL/src/docview.jl:249
 [4] doc(binding::Base.Docs.Binding, sig::Type)
   @ REPL ~/julia-1.7.2/share/julia/stdlib/v1.7/REPL/src/docview.jl:182
 [5] doc(binding::Base.Docs.Binding)
   @ REPL ~/julia-1.7.2/share/julia/stdlib/v1.7/REPL/src/docview.jl:160
 [6] top-level scope
   @ ~/julia-1.7.2/share/julia/stdlib/v1.7/REPL/src/docview.jl:470

julia>

Searched here in this forum

Some one suggest that importing the same file twice cause this warning, but I can’t reproduce with:

julia> import GeometryBasics: Mesh
julia> import GeometryBasics: Mesh
julia>

I can’t do import MakieCore: Mesh, can I?

Searched source code but…

src/Makie.jl has

using MakieCore: Heatmap, [...], Mesh, [...]
export Heatmap, [...], Mesh, [...]

MakieCore/src/basic_plots.jl has a macro with Mesh but I’m not sure exactly what it does

@recipe(Mesh, mesh) do scene
    Attributes(;
        default_theme(scene)...,
        color = :black,
        backlight = 0f0,
        colormap = theme(scene, :colormap),
        colorrange = automatic,
        interpolate = true,
        shading = true,
        fxaa = true,
        inspectable = theme(scene, :inspectable),
        cycle = [:color => :patchcolor],
        space = :data
    )
end
2

Hi, so basically you got it correct: you’re importing the identifier Mesh from two different modules and so Julia is warning you that you probably need to make sure that you’re using the right identifier in your code. You can do that, for example, with

using GLMakie
using GeometryBasics
const Mesh = GeometryBasics.Mesh

That way it’s absolutely clear which identifier the compiler should use. You can still access the other one with GLMakie.Mesh.