fix: improve error message for missing parameter values

Author: AayushSabharwal

src/systems/parameter_buffer.jl

@@ -70,7 +70,7 @@ function MTKParameters(
         end
     end
 
-    isempty(missing_params) || throw(MissingVariablesError(collect(missing_params)))
+    isempty(missing_params) || throw(MissingParametersError(collect(missing_params)))
 
     tunable_buffer = Tuple(Vector{temp.type}(undef, temp.length)
     for temp in ic.tunable_buffer_sizes)
@@ -575,3 +575,17 @@ function as_duals(p::MTKParameters, dualtype)
     discrete = dualtype.(p.discrete)
     return MTKParameters{typeof(tunable), typeof(discrete)}(tunable, discrete)
 end
+
+const MISSING_PARAMETERS_MESSAGE = """
+                                Some parameters are missing from the variable map.
+                                Please provide a value or default for the following variables:
+                                """
+
+struct MissingParametersError <: Exception
+    vars::Any
+end
+
+function Base.showerror(io::IO, e::MissingParametersError)
+    println(io, MISSING_PARAMETERS_MESSAGE)
+    println(io, e.vars)
+end

test/mtkparameters.jl

@@ -130,7 +130,7 @@ u0 = [X => 1.0]
 tspan = (0.0, 100.0)
 ps = [p => 1.0] # Value for `d` is missing
 
-@test_throws ModelingToolkit.MissingVariablesError ODEProblem(sys, u0, tspan, ps)
+@test_throws ModelingToolkit.MissingParametersError ODEProblem(sys, u0, tspan, ps)
 @test_nowarn ODEProblem(sys, u0, tspan, [ps..., d => 1.0])
 
 # JET tests