Fix isvariable

Author: YingboMa

src/ModelingToolkit.jl

@@ -52,7 +52,7 @@ import Symbolics: rename, get_variables!, _solve, hessian_sparsity,
                   ParallelForm, SerialForm, MultithreadedForm, build_function,
                   unflatten_long_ops, rhss, lhss, prettify_expr, gradient,
                   jacobian, hessian, derivative, sparsejacobian, sparsehessian,
-                  substituter, scalarize
+                  substituter, scalarize, getparent
 
 import DiffEqBase: @add_kwonly
 

src/utils.jl

@@ -210,7 +210,12 @@ isdiffeq(eq) = isdifferential(eq.lhs)
 isdifference(expr) = istree(expr) && operation(expr) isa Difference
 isdifferenceeq(eq) = isdifference(eq.lhs)
 
-isvariable(x) = x isa Symbolic && hasmetadata(x, VariableSource)
+function isvariable(x)
+    x isa Symbolic || return false
+    p = getparent(x, nothing)
+    p === nothing || (x = p)
+    hasmetadata(x, VariableSource)
+end
 
 vars(x::Sym; op=Differential) = Set([x])
 vars(exprs::Symbolic; op=Differential) = vars([exprs]; op=op)

src/variables.jl

@@ -12,7 +12,7 @@ Symbolics.option_to_metadata_type(::Val{:input}) = VariableInput
 Symbolics.option_to_metadata_type(::Val{:output}) = VariableOutput
 
 function isvarkind(m, x)
-    p = Symbolics.getparent(x, nothing)
+    p = getparent(x, nothing)
     p === nothing || (x = p)
     getmetadata(x, m, false)
 end

test/odesystem.jl

@@ -399,6 +399,7 @@ eqs = [
 @test isequal(@nonamespace(sys.y), unwrap(y))
 @test isequal(@nonamespace(sys.p), unwrap(p))
 @test_nowarn sys.x, sys.y, sys.p
+@test ModelingToolkit.isvariable(Symbolics.unwrap(x[1]))
 
 # Mixed Difference Differential equations
 @parameters t a b c d