From ca7a2e17137b8e1d8ecf866819b5f3cee2373439 Mon Sep 17 00:00:00 2001
From: contradict <contradict@gmail.com>
Date: Thu, 29 Aug 2024 13:03:49 -0700
Subject: [PATCH 1/2] Fix unit conversion for expressions

When a parameter is specified in terms of other parameters, no unit
conversion should be attempted until the full expression is evaluted.
---
 src/systems/model_parsing.jl |  8 ++++++++
 test/units.jl                | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/systems/model_parsing.jl b/src/systems/model_parsing.jl
index 51a61e33bf..f7466235f5 100644
--- a/src/systems/model_parsing.jl
+++ b/src/systems/model_parsing.jl
@@ -663,6 +663,14 @@ function convert_units(varunits::Unitful.FreeUnits, value::AbstractArray{T}) whe
     Unitful.ustrip.(varunits, value)
 end
 
+function convert_units(varunits::Unitful.FreeUnits, value::Num)
+    value
+end
+
+function convert_units(varunits::DynamicQuantities.Quantity, value::Num)
+    value
+end
+
 function parse_variable_arg(dict, mod, arg, varclass, kwargs, where_types)
     vv, def, metadata_with_exprs = parse_variable_def!(
         dict, mod, arg, varclass, kwargs, where_types)
diff --git a/test/units.jl b/test/units.jl
index 4b8aace4c9..a792ae3400 100644
--- a/test/units.jl
+++ b/test/units.jl
@@ -223,3 +223,21 @@ end
 
 @variables x(t)
 @test ModelingToolkit.get_unit(sin(x)) == ModelingToolkit.unitless
+
+@mtkmodel ExpressionParametersTest begin
+    @parameters begin
+        v = 1.0, [unit = u"m/s"]
+        τ = 1.0, [unit = u"s"]
+    end
+    @components begin
+        pt = ParamTest(; a = v * τ)
+    end
+end
+
+@named sys = ExpressionParametersTest(; v = 2.0u"m/s", τ = 3.0u"s")
+sys = complete(sys)
+# TODO: Is there a way to evalute this expression and compare to 6.0?
+@test isequal(ModelingToolkit.getdefault(sys.pt.a), sys.v * sys.τ)
+@test ModelingToolkit.getdefault(sys.v) ≈ 2.0
+@test ModelingToolkit.getdefault(sys.τ) ≈ 3.0
+

From e078c1d4c835ef3ee051a1ebf29cb2b1854ae2f3 Mon Sep 17 00:00:00 2001
From: contradict <contradict@gmail.com>
Date: Thu, 29 Aug 2024 13:12:27 -0700
Subject: [PATCH 2/2] Fix spelling

---
 test/units.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/units.jl b/test/units.jl
index a792ae3400..f0fcfdfb98 100644
--- a/test/units.jl
+++ b/test/units.jl
@@ -236,7 +236,7 @@ end
 
 @named sys = ExpressionParametersTest(; v = 2.0u"m/s", τ = 3.0u"s")
 sys = complete(sys)
-# TODO: Is there a way to evalute this expression and compare to 6.0?
+# TODO: Is there a way to evaluate this expression and compare to 6.0?
 @test isequal(ModelingToolkit.getdefault(sys.pt.a), sys.v * sys.τ)
 @test ModelingToolkit.getdefault(sys.v) ≈ 2.0
 @test ModelingToolkit.getdefault(sys.τ) ≈ 3.0