Improve error description of setproperty! (#287)

* Add throw error dim mis

* Fix space

* Change assertionerror to dimensionmismatch in test

Author: aurorarossi

src/GNNGraphs/datastore.jl

@@ -109,7 +109,7 @@ function Base.setproperty!(ds::DataStore, s::Symbol, x)
     @assert s != :_n "cannot set _n directly"
     @assert s != :_data "cannot set _data directly"
     if getn(ds) >= 0
-        @assert numobs(x) == getn(ds) "expected (numobs(x) == getn(ds)) but got $(numobs(x)) != $(getn(ds))"
+        numobs(x) == getn(ds) || throw(DimensionMismatch("expected $(getn(ds)) object features but got $(numobs(x))."))
     end
     return getdata(ds)[s] = x
 end

test/GNNGraphs/datastore.jl

@@ -17,7 +17,7 @@ end
     x = rand(10)
     ds = DataStore(10, (:x => x, :y => rand(2, 10)))
     @test ds.x == ds[:x] == x
-    @test_throws AssertionError ds.z=rand(12)
+    @test_throws DimensionMismatch ds.z=rand(12)
     ds.z = [1:10;]
     @test ds.z == [1:10;]
 end