Fix #539 (#540)

* Fix #539

* address review, bump version

* small improvement

Project.toml

@@ -1,7 +1,7 @@
 name = "Manifolds"
 uuid = "1cead3c2-87b3-11e9-0ccd-23c62b72b94e"
 authors = ["Seth Axen <[email protected]>", "Mateusz Baran <[email protected]>", "Ronny Bergmann <[email protected]>", "Antoine Levitt <[email protected]>"]
-version = "0.8.29"
+version = "0.8.30"
 
 [deps]
 Colors = "5ae59095-9a9b-59fe-a467-6f913c188581"

src/manifolds/MetricManifold.jl

@@ -64,12 +64,27 @@ struct MetricManifold{𝔽,M<:AbstractManifold{𝔽},G<:AbstractMetric} <:
     metric::G
 end
 
+function _drop_embedding_type(t::TraitList)
+    return TraitList(t.head, _drop_embedding_type(t.tail))
+end
+function _drop_embedding_type(t::TraitList{IsIsometricEmbeddedManifold})
+    return _drop_embedding_type(t.tail)
+end
+function _drop_embedding_type(t::TraitList{IsEmbeddedSubmanifold})
+    return _drop_embedding_type(t.tail)
+end
+_drop_embedding_type(t::EmptyTrait) = t
+
 function active_traits(f, M::MetricManifold, args...)
+    at = active_traits(f, M.manifold, args...)
+    imf = is_metric_function(f)
+    idm = imf && is_default_metric(M.manifold, M.metric)
     return merge_traits(
-        is_default_metric(M.manifold, M.metric) ? IsDefaultMetric(M.metric) : EmptyTrait(),
+        idm ? IsDefaultMetric(M.metric) : EmptyTrait(),
         IsMetricManifold(),
-        active_traits(f, M.manifold, args...),
-        is_metric_function(f) ? EmptyTrait() : IsExplicitDecorator(),
+        # avoid forwarding to the embedding if the metric is not the default one
+        idm ? at : _drop_embedding_type(at),
+        imf ? EmptyTrait() : IsExplicitDecorator(),
     )
 end
 # remetricise instead of double-decorating

test/metric.jl

@@ -233,6 +233,11 @@ function Manifolds.vector_transport_along!(
     Y .= c
     return Y
 end
+
+# test for https://github.com/JuliaManifolds/Manifolds.jl/issues/539
+struct Issue539Metric <: RiemannianMetric end
+Manifolds.inner(::MetricManifold{ℝ,<:AbstractManifold{ℝ},Issue539Metric}, p, X, Y) = 3
+
 @testset "Metrics" begin
     # some tests failed due to insufficient accuracy for a particularly bad RNG state
     Random.seed!(42)
@@ -640,4 +645,16 @@ end
         Y2 = change_representer(M, G, p, X)
         @test Y2 ≈ 2 .* X #scaled metric has a factor 2, removing introduces this factor
     end
+
+    @testset "issue #539" begin
+        M = Sphere(2)
+        p = [0.49567358314486515, 0.3740229181343087, -0.7838460025302334]
+        X = [-1.1552859627097727, 0.40665559717366767, -0.5365163797547751]
+        MM = MetricManifold(M, Issue539Metric())
+        @test norm(MM, p, X)^2 ≈ 3
+        @test Manifolds._drop_embedding_type(
+            ManifoldsBase.merge_traits(IsEmbeddedSubmanifold()),
+        ) === ManifoldsBase.EmptyTrait()
+        @test get_embedding(MM) === get_embedding(M)
+    end
 end