Refuse Unitful conversion when preferunits has been called

Author: MilesCranmer

ext/DynamicQuantitiesUnitfulExt.jl

@@ -13,7 +13,12 @@ end
 # This lets the user override the preferred units:
 function unitful_equivalences()
     si_units = (length=u"m", mass=u"kg", time=u"s", current=u"A", temperature=u"K", luminosity=u"cd", amount=u"mol")
-    return NamedTuple((k => Unitful.upreferred(si_units[k]) for k in keys(si_units)))
+    for k in keys(si_units)
+        if Unitful.upreferred(si_units[k]) !== si_units[k]
+            error("Found custom `Unitful.preferunits`. This is not supported when interfacing Unitful and DynamicQuantities: you must leave the default `Unitful.upreferred`, which is the SI base units.")
+        end
+    end
+    return NamedTuple((k => si_units[k] for k in keys(si_units)))
 end
 
 Base.convert(::Type{Unitful.Quantity}, x::DynamicQuantities.Quantity) =

test/test_unitful.jl

@@ -6,18 +6,13 @@ import Ratios: SimpleRatio
 import SaferIntegers: SafeInt16
 using Test
 
-# Try to work with different preferred units:
-Unitful.preferunits(u"km")
-
 risapprox(x::Unitful.Quantity, y::Unitful.Quantity; kws...) =
     let (xfloat, yfloat) = (Unitful.ustrip ∘ Unitful.upreferred).((x, y))
         return isapprox(xfloat, yfloat; kws...)
     end
 
-factor_for_preferred_units = 1e-3
-
 for T in [DEFAULT_VALUE_TYPE, Float16, Float32, Float64], R in [DEFAULT_DIM_TYPE, Rational{Int16}, Rational{Int32}, SimpleRatio{Int}, SimpleRatio{SafeInt16}]
-    x = DynamicQuantities.Quantity(T(0.2*factor_for_preferred_units), R, length=1, amount=2, current=-1 // 2, luminosity=2 // 5)
+    x = DynamicQuantities.Quantity(T(0.2), R, length=1, amount=2, current=-1 // 2, luminosity=2 // 5)
     x_unitful = T(0.2)u"m*mol^2*A^(-1//2)*cd^(2//5)"
 
     @test risapprox(convert(Unitful.Quantity, x), x_unitful; atol=1e-6)