fix: Add metadata getters

docs/src/basics/Variable_metadata.md

@@ -54,6 +54,10 @@ using ModelingToolkit: t_nounits as t, D_nounits as D
 
 @variables i(t) [connect = Flow]
 @variables k(t) [connect = Stream]
+hasconnect(i)
+```
+```@example connect
+getconnect(k)
 ```
 
 ## Input or output
@@ -177,8 +181,44 @@ A variable can be marked `irreducible` to prevent it from being moved to an
 `observed` state. This forces the variable to be computed during solving so that
 it can be accessed in [callbacks](@ref events)
 
-```julia
+```@example metadata
 @variable important_value [irreducible = true]
+isirreducible(important_value)
+```
+
+## State Priority
+
+When a model is structurally simplified, the algorithm will try to ensure that the variables with higher state priority become states of the system. A variable's state priority is a number set using the `state_priority` metadata.
+
+```@example metadata
+@variable important_dof [state_priority = 10] unimportant_dof [state_priority = 2]
+state_priority(important_dof)
+```
+
+## Units
+
+Units for variables can be designated using symbolic metadata. For more information, please see the [model validation and units](@ref units) section of the docs. Note that `getunit` is not equivalent to `get_unit` - the former is a metadata getter for individual variables (and is provided so the same interface function for `unit` exists like other metadata), while the latter is used to handle more general symbolic expressions. 
+
+```@example metadata
+@variable speed [unit=u"m/s"]
+hasunit(speed)
+```
+```@example metadata
+getunit(speed)
+```
+
+## Miscellaneous metadata
+
+User-defined metadata can be added using the `misc` metadata. This can be queried
+using the `hasmisc` and `getmisc` functions.
+
+```@example metadata
+@variables u [misc = :conserved_parameter] y [misc = [2, 4, 6]]
+hasmisc(u)
+```
+
+```@example metadata
+getmisc(y)
 ```
 
 ## Additional functions

src/ModelingToolkit.jl

@@ -246,7 +246,9 @@ export initial_state, transition, activeState, entry, ticksInState, timeInState
 export @component, @mtkmodel, @mtkbuild
 export isinput, isoutput, getbounds, hasbounds, getguess, hasguess, isdisturbance,
        istunable, getdist, hasdist,
-       tunable_parameters, isirreducible, getdescription, hasdescription
+       tunable_parameters, isirreducible, getdescription, hasdescription,
+       hasunit, getunit, hasconnect, getconnect,
+       hasmisc, getmisc
 export ode_order_lowering, dae_order_lowering, liouville_transform
 export PDESystem
 export Differential, expand_derivatives, @derivatives

src/variables.jl

@@ -8,7 +8,6 @@ struct VariableStatePriority end
 struct VariableMisc end
 Symbolics.option_to_metadata_type(::Val{:unit}) = VariableUnit
 Symbolics.option_to_metadata_type(::Val{:connect}) = VariableConnectType
-Symbolics.option_to_metadata_type(::Val{:noise}) = VariableNoiseType
 Symbolics.option_to_metadata_type(::Val{:input}) = VariableInput
 Symbolics.option_to_metadata_type(::Val{:output}) = VariableOutput
 Symbolics.option_to_metadata_type(::Val{:irreducible}) = VariableIrreducible
@@ -29,7 +28,7 @@ ModelingToolkit.dump_variable_metadata(p)
 """
 function dump_variable_metadata(var)
     uvar = unwrap(var)
-    vartype, name = get(uvar.metadata, VariableSource, (:unknown, :unknown))
+    variable_source, name = Symbolics.getmetadata(uvar, VariableSource, (:unknown, :unknown))
     type = symtype(uvar)
     if type <: AbstractArray
         shape = Symbolics.shape(var)
@@ -39,14 +38,13 @@ function dump_variable_metadata(var)
     else
         shape = nothing
     end
-    unit = get(uvar.metadata, VariableUnit, nothing)
-    connect = get(uvar.metadata, VariableConnectType, nothing)
-    noise = get(uvar.metadata, VariableNoiseType, nothing)
+    unit = getunit(uvar)
+    connect = getconnect(uvar)
     input = isinput(uvar) || nothing
     output = isoutput(uvar) || nothing
-    irreducible = get(uvar.metadata, VariableIrreducible, nothing)
-    state_priority = get(uvar.metadata, VariableStatePriority, nothing)
-    misc = get(uvar.metadata, VariableMisc, nothing)
+    irreducible = isirreducible(var)
+    state_priority = Symbolics.getmetadata(uvar, VariableStatePriority, nothing)
+    misc = getmisc(uvar)
     bounds = hasbounds(uvar) ? getbounds(uvar) : nothing
     desc = getdescription(var)
     if desc == ""
@@ -57,16 +55,16 @@ function dump_variable_metadata(var)
     disturbance = isdisturbance(uvar) || nothing
     tunable = istunable(uvar, isparameter(uvar))
     dist = getdist(uvar)
-    type = symtype(uvar)
+    variable_type = getvariabletype(uvar)
 
     meta = (
         var = var,
-        vartype,
+        variable_source,
         name,
+        variable_type,
         shape,
         unit,
         connect,
-        noise,
         input,
         output,
         irreducible,
@@ -85,11 +83,28 @@ function dump_variable_metadata(var)
     return NamedTuple(k => v for (k, v) in pairs(meta) if v !== nothing)
 end
 
+### Connect
 abstract type AbstractConnectType end
 struct Equality <: AbstractConnectType end # Equality connection
 struct Flow <: AbstractConnectType end     # sum to 0
 struct Stream <: AbstractConnectType end   # special stream connector
 
+"""
+    getconnect(x)
+
+Get the connect type of x. See also [`hasconnect`](@ref).
+"""
+getconnect(x) = getconnect(unwrap(x))
+getconnect(x::Symbolic) = Symbolics.getmetadata(x, VariableConnectType, nothing)
+"""
+    hasconnect(x)
+
+Determine whether variable `x` has a connect type. See also [`getconnect`](@ref).
+"""
+hasconnect(x) = getconnect(x) !== nothing
+setconnect(x, t::Type{T}) where T <: AbstractConnectType = setmetadata(x, VariableConnectType, t)
+
+### Input, Output, Irreducible 
 isvarkind(m, x::Union{Num, Symbolics.Arr}) = isvarkind(m, value(x))
 function isvarkind(m, x)
     iskind = getmetadata(x, m, nothing)
@@ -98,15 +113,17 @@ function isvarkind(m, x)
     getmetadata(x, m, false)
 end
 
-setinput(x, v) = setmetadata(x, VariableInput, v)
-setoutput(x, v) = setmetadata(x, VariableOutput, v)
-setio(x, i, o) = setoutput(setinput(x, i), o)
+setinput(x, v::Bool) = setmetadata(x, VariableInput, v)
+setoutput(x, v::Bool) = setmetadata(x, VariableOutput, v)
+setio(x, i::Bool, o::Bool) = setoutput(setinput(x, i), o)
+
 isinput(x) = isvarkind(VariableInput, x)
 isoutput(x) = isvarkind(VariableOutput, x)
+
 # Before the solvability check, we already have handled IO variables, so
 # irreducibility is independent from IO.
 isirreducible(x) = isvarkind(VariableIrreducible, x)
-setirreducible(x, v) = setmetadata(x, VariableIrreducible, v)
+setirreducible(x, v::Bool) = setmetadata(x, VariableIrreducible, v)
 state_priority(x) = convert(Float64, getmetadata(x, VariableStatePriority, 0.0))::Float64
 
 function default_toterm(x)
@@ -545,3 +562,38 @@ function get_default_or_guess(x)
         return getguess(x)
     end
 end
+
+## Miscellaneous metadata ======================================================================
+"""
+    getmisc(x)
+
+Fetch any miscellaneous data associated with symbolic variable `x`.
+See also [`hasmisc(x)`](@ref).
+"""
+getmisc(x) = getmisc(unwrap(x))
+getmisc(x::Symbolic) = Symbolics.getmetadata(x, VariableMisc, nothing)
+"""
+    hasmisc(x)
+
+Determine whether a symbolic variable `x` has misc
+metadata associated with it. 
+
+See also [`getmisc(x)`](@ref).
+"""
+hasmisc(x) = getmisc(x) !== nothing
+setmisc(x, miscdata) = setmetadata(x, VariableMisc, miscdata) 
+
+## Units ======================================================================
+"""
+    getunit(x)
+
+Fetch the unit associated with variable `x`. This function is a metadata getter for an individual variable, while `get_unit` is used for unit inference on more complicated sdymbolic expressions.
+"""
+getunit(x) = getunit(unwrap(x))
+getunit(x::Symbolic) = Symbolics.getmetadata(x, VariableUnit, nothing)
+"""
+    hasunit(x)
+
+Check if the variable `x` has a unit.
+"""
+hasunit(x) = getunit(x) !== nothing

test/test_variable_metadata.jl

@@ -1,4 +1,5 @@
 using ModelingToolkit
+using DynamicQuantities
 
 # Bounds
 @variables u [bounds = (-1, 1)]
@@ -185,3 +186,42 @@ params_meta = ModelingToolkit.dump_parameters(sys)
 params_meta = Dict([ModelingToolkit.getname(meta.var) => meta for meta in params_meta])
 @test params_meta[:p].default == 3.0
 @test isequal(params_meta[:q].dependency, 2p)
+
+# Connect
+@variables x [connect = Flow]
+@test hasconnect(x)
+@test getconnect(x) == Flow
+@test ModelingToolkit.dump_variable_metadata(x).connect == Flow
+x = ModelingToolkit.setconnect(x, ModelingToolkit.Stream)
+@test getconnect(x) == ModelingToolkit.Stream
+
+struct BadConnect end
+@test_throws Exception ModelingToolkit.setconnect(x, BadConnect)
+
+# Unit
+@variables x [unit = u"s"]
+@test hasunit(x)
+@test getunit(x) == u"s"
+@test ModelingToolkit.dump_variable_metadata(x).unit == u"s"
+
+# Misc data
+@variables x [misc = [:good]]
+@test hasmisc(x)
+@test getmisc(x) == [:good]
+x = ModelingToolkit.setmisc(x, "okay")
+@test getmisc(x) == "okay"
+
+# Variable Type
+@variables x
+@test ModelingToolkit.getvariabletype(x) == ModelingToolkit.VARIABLE
+@test ModelingToolkit.dump_variable_metadata(x).variable_type == ModelingToolkit.VARIABLE
+@test ModelingToolkit.dump_variable_metadata(x).variable_source == :variables
+x = ModelingToolkit.toparam(x)
+@test ModelingToolkit.getvariabletype(x) == ModelingToolkit.PARAMETER
+@test ModelingToolkit.dump_variable_metadata(x).variable_source == :variables
+
+@parameters y
+@test ModelingToolkit.getvariabletype(y) == ModelingToolkit.PARAMETER
+
+@brownian z
+@test ModelingToolkit.getvariabletype(z) == ModelingToolkit.BROWNIAN