Add unit and connect metadata

Author: YingboMa

src/variables.jl

@@ -1,3 +1,8 @@
+struct VariableUnit end
+struct VariableConnectType end
+Symbolics.option_to_metadata_type(::Val{:unit}) = VariableUnit
+Symbolics.option_to_metadata_type(::Val{:connect}) = VariableConnectType
+
 """
 $(SIGNATURES)
 Takes a list of pairs of `variables=>values` and an ordered list of variables

test/variable_parsing.jl

@@ -63,3 +63,58 @@ x1 = Num[Variable{FnType{Tuple{Any}, Real}}(:x, 1)(t.val),
 
 @variables a[1:11,1:2]
 @variables a()
+
+using Symbolics: value, VariableDefaultValue
+using ModelingToolkit: VariableConnectType, VariableUnit, rename
+using Unitful
+
+vals = [1,2,3,4]
+@variables x=1 xs[1:4]=vals ys[1:5]=1
+
+@test getmetadata(x, VariableDefaultValue) === 1
+@test getmetadata.(xs, (VariableDefaultValue,)) == vals
+@test getmetadata.(ys, (VariableDefaultValue,)) == ones(Int, 5)
+
+struct Flow end
+u = u"m^3/s"
+@variables begin
+    x = [1, 2], [connect=Flow,unit=u]
+    y = 2
+end
+
+@test getmetadata(x, VariableDefaultValue) == [1, 2]
+@test getmetadata(x, VariableConnectType) == Flow
+@test getmetadata(x, VariableUnit) == u
+@test getmetadata(y, VariableDefaultValue) === 2
+
+@variables begin
+    x, [connect=Flow,unit=u]
+    y = 2, [connect=Flow]
+end
+
+@test !hasmetadata(x, VariableDefaultValue)
+@test getmetadata(x, VariableConnectType) == Flow
+@test getmetadata(x, VariableUnit) == u
+@test getmetadata(y, VariableDefaultValue) === 2
+@test getmetadata(y, VariableConnectType) == Flow
+
+a = rename(value(x), :a)
+@test !hasmetadata(x, VariableDefaultValue)
+@test getmetadata(x, VariableConnectType) == Flow
+@test getmetadata(x, VariableUnit) == u
+
+@variables t x(t)=1 [connect=Flow,unit=u]
+
+@test getmetadata(x, VariableDefaultValue) == 1
+@test getmetadata(x, VariableConnectType) == Flow
+@test getmetadata(x, VariableUnit) == u
+
+a = rename(value(x), :a)
+@test getmetadata(a, VariableDefaultValue) == 1
+@test getmetadata(a, VariableConnectType) == Flow
+@test getmetadata(a, VariableUnit) == u
+
+@parameters p=2 [unit=u"m",]
+@test getmetadata(p, VariableDefaultValue) == 2
+@test !hasmetadata(p, VariableConnectType)
+@test getmetadata(p, VariableUnit) == u"m"