fix(): better error message for datavar creation

Author: Dmitri Bagaev

Project.toml

@@ -1,7 +1,7 @@
 name = "GraphPPL"
 uuid = "b3f8163a-e979-4e85-b43e-1f63d8c8b42c"
 authors = ["Dmitry Bagaev <[email protected]>"]
-version = "2.0.0"
+version = "2.0.1"
 
 [deps]
 MacroTools = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"

docs/src/transformation-steps.md

@@ -37,7 +37,8 @@ y = datavar(args...) where { options... }
 is translated to 
 
 ```
-y = datavar(var"#model", options, :y, ensure_type(args[1]), args[2:end]...)
+ensure_type(args[1]) || error(...)
+y = datavar(var"#model", options, :y, args[1], args[2:end]...)
 ```
 
 where `var"#model"` references to an hidden model variable, `ensure_type` function ensures that the first argument is a valid type object, rest of the arguments are left untouched. 

src/backends/reactivemp.jl

@@ -87,7 +87,9 @@ function write_randomvar_expression(::ReactiveMPBackend, model, varexp, options,
 end
 
 function write_datavar_expression(::ReactiveMPBackend, model, varexpr, options, type, arguments)
-    return :($varexpr = ReactiveMP.datavar($model, $options, $(GraphPPL.fquote(varexpr)), ReactiveMP.PointMass{ GraphPPL.ensure_type($(type)) }, $(arguments...)))
+    errstr    = "The expression `$varexpr = datavar($(type))` is incorrect. datavar(::Type, [ dims... ]) requires `Type` as a first argument, but `$(type)` is not a `Type`."
+    checktype = :(GraphPPL.ensure_type($(type)) || error($errstr))
+    return :($checktype; $varexpr = ReactiveMP.datavar($model, $options, $(GraphPPL.fquote(varexpr)), ReactiveMP.PointMass{ $type }, $(arguments...)))
 end
 
 function write_constvar_expression(::ReactiveMPBackend, model, varexpr, arguments)
@@ -326,7 +328,7 @@ function write_datavar_options(::ReactiveMPBackend, variable, type, options)
         end
     end
 
-    return :(ReactiveMP.DataVariableCreationOptions(ReactiveMP.PointMass{ GraphPPL.ensure_type($type) }, $subject_option, $allow_missing_option))
+    return :(ReactiveMP.DataVariableCreationOptions(ReactiveMP.PointMass{ $type }, $subject_option, $allow_missing_option))
 end
 
 function write_default_model_constraints(::ReactiveMPBackend)

src/model.jl

@@ -15,12 +15,6 @@ fquote(expr::Symbol) = Expr(:quote, expr)
 fquote(expr::Int)    = expr
 fquote(expr::Expr)   = expr
 
-"""
-    ensure_type
-"""
-ensure_type(x::Type) = x
-ensure_type(x)       = error("Valid type object was expected but '$x' has been found")
-
 is_kwargs_expression(x)       = false
 is_kwargs_expression(x::Expr) = x.head === :parameters
 
@@ -293,7 +287,7 @@ function generate_model_expression(backend, model_options, model_specification)
         # Step 2.1 Convert datavar calls
         if @capture(expression, varexpr_ = datavar(arguments__; options__)) 
             @assert varexpr ∉ varids "Invalid model specification: '$varexpr' id is duplicated"
-            @assert length(arguments) >= 1 "Invalid datavar() creation. datavar(::Type{T}, [ dims... ]) requires type specification as a first argument, but the expression `$(expression)` has no type argument."
+            @assert length(arguments) >= 1 "The expression `$expression` is incorrect. datavar(::Type, [ dims... ]) requires `Type` as a first argument."
 
             push!(varids, varexpr)
 

src/utils.jl

@@ -39,4 +39,12 @@ Shorthand for `ishead(expr, :ref)`.
 
 See also: [`ishead`](@ref)
 """
-isref(expr) = ishead(expr, :ref)
+isref(expr) = ishead(expr, :ref)
+
+"""
+    ensure_type(x)
+
+Checks if `x` is of type `Type` 
+"""
+ensure_type(x::Type) = true
+ensure_type(x)       = false

test/utils.jl

@@ -54,4 +54,13 @@ end
 
 end
 
+@testset "ensure_type tests" begin 
+    import GraphPPL: ensure_type
+
+    @test ensure_type(Int) === true
+    @test ensure_type(1) === false
+    @test ensure_type(Float64) === true
+    @test ensure_type(1.0) === false
+end
+
 end