Add a more informative error message, when no backend is loaded.

Author: felixcremer

src/datasets/datasetinterface.jl

@@ -78,6 +78,7 @@ backendregex = Pair[]
 
 function backendfrompath(g::String; driver = :all)
   if driver == :all
+    isempty(backendregex) && throw("No backend found. Load a backend by using the corresponding package.")
     for p in YAXArrayBase.backendregex
       if match(p[1],g) !== nothing
         return p[2]

test/datasets.jl

@@ -1,4 +1,9 @@
-using YAXArrayBase, NetCDF, Zarr, Test
+using YAXArrayBase, Test
+@testset "Empty Backend" begin
+  @test_throws "No backend found." YAXArrayBase.backendfrompath("test.zarr")
+end
+
+using NetCDF, Zarr
 
 @testset "Reading NetCDF" begin
 import Downloads

test/runtests.jl

@@ -1,8 +1,9 @@
 using YAXArrayBase
 using Test
-@testset "Arrays" begin
-  include("arrays.jl")
-end
+
 @testset "Datasets" begin
 include("datasets.jl")
 end
+@testset "Arrays" begin
+  include("arrays.jl")
+end