Add helpful message when ProductManifold is used without RAT.jl (#201)

* Change representation_size of ProductManifold to undefined

* add error message

* fix PowerManifold

* reorder tests

NEWS.md

@@ -5,6 +5,16 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.15.14] 27/08/2024
+
+### Added
+
+* A helpful error message when `ProductManifold` is used without `RecursiveArrayTools.jl`.
+
+### Changed
+
+* `representation_size` for `ProductManifold` now returns `nothing` instead of a one-element tuple. This change makes it easier to notice errors caused by not having `RecursiveArrayTools.jl` loaded.
+
 ## [0.15.13] 10/08/2024
 
 ### Changed

Project.toml

@@ -1,7 +1,7 @@
 name = "ManifoldsBase"
 uuid = "3362f125-f0bb-47a3-aa74-596ffd7ef2fb"
 authors = ["Seth Axen <seth.axen@gmail.com>", "Mateusz Baran <mateuszbaran89@gmail.com>", "Ronny Bergmann <manopt@ronnybergmann.net>", "Antoine Levitt <antoine.levitt@gmail.com>"]
-version = "0.15.13"
+version = "0.15.14"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/ManifoldsBase.jl

@@ -179,7 +179,16 @@ isomorphisms.
 end
 @inline function allocate_result(M::AbstractManifold, f)
     T = allocate_result_type(M, f, ())
-    return Array{T}(undef, representation_size(M)...)
+    rs = representation_size(M)
+    if isnothing(rs)
+        msg = "Could not allocate result of function $f on manifold $M."
+        if M isa ProductManifold
+            msg *= " This error could be resolved by importing RecursiveArrayTools.jl. If this is not the case, please open report an issue."
+        end
+        error(msg)
+    else
+        return Array{T}(undef, rs...)
+    end
 end
 
 """

src/PowerManifold.jl

@@ -1319,7 +1319,7 @@ end
 
 Base.@propagate_inbounds @inline function _read(
     M::AbstractPowerManifold,
-    rep_size::Tuple,
+    rep_size::Union{Tuple,Nothing},
     x::AbstractArray,
     i::Int,
 )
@@ -1328,7 +1328,7 @@ end
 
 Base.@propagate_inbounds @inline function _read(
     ::Union{PowerManifoldNested,PowerManifoldNestedReplacing},
-    rep_size::Tuple,
+    rep_size::Union{Tuple,Nothing},
     x::AbstractArray,
     i::Tuple,
 )
@@ -1765,15 +1765,25 @@ function Weingarten!(M::AbstractPowerManifold, Y, p, X, V)
     return Y
 end
 
-@inline function _write(M::AbstractPowerManifold, rep_size::Tuple, x::AbstractArray, i::Int)
+@inline function _write(
+    M::AbstractPowerManifold,
+    rep_size::Union{Tuple,Nothing},
+    x::AbstractArray,
+    i::Int,
+)
     return _write(M, rep_size, x, (i,))
 end
 
 @inline function _is_nested_write_getindex(::PowerManifoldNested, x)
     return !isbitstype(eltype(x))
 end
 
-@inline function _write(M::PowerManifoldNested, ::Tuple, x::AbstractArray, i::Tuple)
+@inline function _write(
+    M::PowerManifoldNested,
+    ::Union{Tuple,Nothing},
+    x::AbstractArray,
+    i::Tuple,
+)
     if _is_nested_write_getindex(M, x)
         return x[i...]
     else

src/ProductManifold.jl

@@ -876,8 +876,8 @@ function retract!(
     return q
 end
 
-function representation_size(M::ProductManifold)
-    return (mapreduce(m -> prod(representation_size(m)), +, M.manifolds),)
+function representation_size(::ProductManifold)
+    return nothing
 end
 
 @doc raw"""

test/product_manifold.jl

@@ -5,12 +5,21 @@ using ManifoldsBase:
     AbstractNumbers, ℝ, ℂ, NestedReplacingPowerRepresentation, ProductBasisData
 using LinearAlgebra
 using Random
-using RecursiveArrayTools
 
-s = @__DIR__
+s = (@__DIR__) * "/test/"
 !(s in LOAD_PATH) && (push!(LOAD_PATH, s))
 using ManifoldsBaseTestUtils
 
+@testset "Product manifold without RecursiveArrayTools.jl" begin
+    M1 = TestSphere(2)
+    M2 = ManifoldsBase.DefaultManifold(2, 2)
+
+    M = ProductManifold(M1, M2)
+    @test_throws ErrorException rand(M)
+end
+
+using RecursiveArrayTools
+
 @testset "Product manifold" begin
     M1 = TestSphere(2)
     M2 = ManifoldsBase.DefaultManifold(2, 2)
@@ -157,7 +166,7 @@ using ManifoldsBaseTestUtils
 
     @testset "Basic operations" begin
         @test manifold_dimension(M) == 6
-        @test representation_size(M) == (7,)
+        @test representation_size(M) === nothing
         @test distance(M, p1, p2) ≈ 4.551637188998299
         qr = similar(p1)
         exp!(M, qr, p1, X1)

test/runtests.jl

@@ -32,11 +32,11 @@ using ManifoldsBase
     include("validation_manifold.jl")
     include("embedded_manifold.jl")
     include("test_sphere.jl")
+    include("product_manifold.jl")
     include("power.jl")
     include("domain_errors.jl")
     include("vector_transport.jl")
     include("metric.jl")
-    include("product_manifold.jl")
     include("fibers.jl")
     include("numerical_checks.jl")
 end