Merge pull request #80 from jkrumbiegel/jk/symbolic-conversion-error

Add informative error when converting symbolic dimensions to Unitful

Author: MilesCranmer

ext/DynamicQuantitiesUnitfulExt.jl

@@ -28,6 +28,9 @@ Base.convert(::Type{Unitful.Quantity}, x::DynamicQuantities.Quantity) =
         validate_upreferred()
         cumulator = DynamicQuantities.ustrip(x)
         dims = DynamicQuantities.dimension(x)
+        if dims isa DynamicQuantities.SymbolicDimensions
+            throw(ArgumentError("Conversion of a `DynamicQuantities.Quantity` to a `Unitful.Quantity` is not defined with dimensions of type `SymbolicDimensions`. Instead, you can first use the `uexpand` function to convert the dimensions to their base SI form of type `Dimensions`, then convert this quantity to a `Unitful.Quantity`."))
+        end
         equiv = unitful_equivalences()
         for dim in keys(dims)
             value = dims[dim]

test/test_unitful.jl

@@ -38,3 +38,8 @@ x = 1.0u"scale"
 @test typeof(x) <: Unitful.Quantity{Float64, MyScaleUnit.𝐒}
 @test_throws ErrorException convert(DynamicQuantities.Quantity, x)
 # These are not supported because there is no SI equivalency
+
+# issue 79
+symbolic = DynamicQuantities.us"s"
+@test_throws ArgumentError convert(Unitful.Quantity, symbolic)
+@test convert(Unitful.Quantity, DynamicQuantities.uexpand(symbolic)) == 1.0 * Unitful.u"s"