From d95a0829fa81adb62e93629569797b9a2776c356 Mon Sep 17 00:00:00 2001
From: Kipton Barros <kbarros@gmail.com>
Date: Sun, 12 Nov 2023 11:50:05 -0700
Subject: [PATCH] Informative errors for Pkg extensions

---
 src/Sunny.jl | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/Sunny.jl b/src/Sunny.jl
index 8e22635d1..dcb71a6a2 100644
--- a/src/Sunny.jl
+++ b/src/Sunny.jl
@@ -146,13 +146,21 @@ export propose_uniform, propose_flip, propose_delta, @mix_proposals, LocalSample
 
 include("deprecated.jl")
 
+isloaded(pkg::String) = any(k -> k.name == pkg, keys(Base.loaded_modules))
+
 ### ext/PlottingExt.jl, dependent on Makie
-function plot_spins end
-function view_crystal end
+function plot_spins(args...)
+    error(isloaded("Makie") ? "Invalid method call" : "Import GLMakie or GLMakie to enable plotting")
+end
+function view_crystal(args...)
+    error(isloaded("Makie") ? "Invalid method call" : "Import GLMakie or GLMakie to enable plotting")
+end
 export plot_spins, view_crystal
 
 ### ext/ExportVTKExt.jl, dependent on WriteVTK
-function export_vtk end
+function export_vtk(args...)
+    error(isloaded("WriteVTK") ? "Invalid method call" : "Import WriteVTK to enable exporting.")
+end
 export export_vtk
 
 end