Add NoAutoDiff (#126)

* Add NoAutoDiff

* Add custom NoAutoDiffAvailable exception

* Bump package version

* Rename NoAutoDiffAvailable to NoAutoDiffSelected

* Rename NoAutoDiffSelected to NoAutoDiffSelectedError

* Apply suggestions from code review

---------

Co-authored-by: Guillaume Dalle <22795598+gdalle@users.noreply.github.com>

Author: oschulz

Project.toml

@@ -1,7 +1,7 @@
 name = "ADTypes"
 uuid = "47edcb42-4c32-4615-8424-f2b9edc5f35b"
 authors = ["Vaibhav Dixit <vaibhavyashdixit@gmail.com>, Guillaume Dalle and contributors"]
-version = "1.17.0"
+version = "1.18.0"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

docs/src/index.md

@@ -92,6 +92,13 @@ ADTypes.symmetric_coloring
 ADTypes.NoColoringAlgorithm
 ```
 
+## No automatic differentiation
+
+```@docs
+NoAutoDiff
+NoAutoDiffSelectedError
+```
+
 ## Modes
 
 ```@docs

src/ADTypes.jl

@@ -45,7 +45,9 @@ export AutoChainRules,
        AutoTapir,
        AutoTaylorDiff,
        AutoTracker,
-       AutoZygote
+       AutoZygote,
+       NoAutoDiff,
+       NoAutoDiffSelectedError
 @public AbstractMode
 @public ForwardMode, ReverseMode, ForwardOrReverseMode, SymbolicMode
 @public mode

src/dense.jl

@@ -515,3 +515,35 @@ Defined by [ADTypes.jl](https://github.com/SciML/ADTypes.jl).
 struct AutoZygote <: AbstractADType end
 
 mode(::AutoZygote) = ReverseMode()
+
+"""
+    NoAutoDiff
+
+Struct used to select no automatic differentiation.
+
+Defined by [ADTypes.jl](https://github.com/SciML/ADTypes.jl).
+
+# Constructors
+
+    NoAutoDiff()
+"""
+struct NoAutoDiff <: AbstractADType end
+
+"""
+    NoAutoDiffSelectedError <: Exception
+
+Signifies that code tried to use automatic differentiation, but [`NoAutoDiff`](@ref) was specified.
+
+# Constructor
+
+    NoAutoDiffSelectedError(msg::String)
+"""
+struct NoAutoDiffSelectedError <: Exception
+    msg::String
+end
+
+NoAutoDiffSelectedError() = NoAutoDiffSelectedError("Automatic differentiation can not be used with NoAutoDiff()")
+
+function mode(::NoAutoDiff)
+    throw(NoAutoDiffSelectedError())
+end

src/symbols.jl

@@ -1,5 +1,6 @@
 """
     ADTypes.Auto(package::Symbol)
+    ADTypes.Auto(nothing)::NoAutoDiff
 
 A shortcut that converts an AD package name into an instance of [`AbstractADType`](@ref), with all parameters set to their default values.
 
@@ -27,3 +28,5 @@ for backend in (:ChainRules, :Diffractor, :Enzyme, :FastDifferentiation,
     @eval Auto(::Val{$(QuoteNode(backend))}, args...; kws...) = $(Symbol(:Auto, backend))(
         args...; kws...)
 end
+
+Auto(::Nothing) = NoAutoDiff()

test/dense.jl

@@ -226,3 +226,10 @@ end
     @test ad isa AutoZygote
     @test mode(ad) isa ReverseMode
 end
+
+@testset "NoAutoDiff" begin
+    ad = NoAutoDiff()
+    @test ad isa AbstractADType
+    @test ad isa NoAutoDiff
+    @test_throws NoAutoDiffSelectedError mode(ad)
+end

test/symbols.jl

@@ -15,6 +15,7 @@ using Test
 @test ADTypes.Auto(:Tapir) isa AutoTapir
 @test ADTypes.Auto(:Tracker) isa AutoTracker
 @test ADTypes.Auto(:Zygote) isa AutoZygote
+@test ADTypes.Auto(nothing) isa NoAutoDiff
 
 @test_throws MethodError ADTypes.Auto(:ThisPackageDoesNotExist)
 @test_throws UndefKeywordError ADTypes.Auto(:ChainRules)