Printing order of base units according to the recipe fixed

src/include/units/bits/unit_text.h

@@ -104,20 +104,33 @@ constexpr auto derived_dimension_unit_text(exp_list<Es...> list)
   return derived_dimension_unit_text(list, std::index_sequence_for<Es...>());
 }
 
-template<typename... Es>
+template<Exponent... Es>
-constexpr bool all_named(exp_list<Es...>)
+constexpr auto exp_list_with_named_units(exp_list<Es...>);
+
+template<Exponent Exp>
+constexpr auto exp_list_with_named_units(Exp)
 {
-  return (dimension_unit<typename Es::dimension>::is_named && ...);
+  using dim = Exp::dimension;
+  if constexpr(dimension_unit<dim>::is_named) {
+    return exp_list<Exp>();
+  }
+  else {
+    using recipe = dim::recipe;
+    return exp_list_with_named_units(recipe());
+  }
+}
+
+template<Exponent... Es>
+constexpr auto exp_list_with_named_units(exp_list<Es...>)
+{
+  return type_list_join<decltype(exp_list_with_named_units(Es()))...>();
 }
 
 template<Dimension Dim>
 constexpr auto derived_dimension_unit_text()
 {
-  using recipe = typename Dim::recipe;
+  using recipe = Dim::recipe;
-  if constexpr(all_named(recipe()))
+  return derived_dimension_unit_text(exp_list_with_named_units(recipe()));
-    return derived_dimension_unit_text(recipe());
-  else
-    return derived_dimension_unit_text(typename Dim::exponents());
 }
 
 // TODO Inline below concept when switched to gcc-10

test/unit_test/runtime/fmt_units_test.cpp

@@ -21,7 +21,9 @@
 // SOFTWARE.
 
 #include "units/physical/si/area.h"
+#include "units/physical/si/constants.h"
 #include "units/physical/si/frequency.h"
+#include "units/physical/si/momentum.h"
 #include "units/physical/si/power.h"
 #include "units/physical/si/velocity.h"
 #include "units/physical/si/volume.h"
@@ -150,6 +152,11 @@ TEST_CASE("fmt::format on synthesized unit symbols", "[text][fmt]")
     CHECK(fmt::format("{}", 1q_mps2) == "1 m/s²");
   }
 
+  SECTION("momentum")
+  {
+    CHECK(fmt::format("{}", 1q_kgmps) == "1 kg⋅m/s");
+  }
+
   SECTION("energy")
   {
     CHECK(fmt::format("{}", 1q_mJ) == "1 mJ");