Make ChainRulesCore a weak dependency on Julia >= 1.9 (#85)

* Make ChainRulesCore a weak dependency on Julia >= 1.9

* Qualify `normalization`

* Check on nightly if extension works correctly

.github/workflows/CI.yml

@@ -15,7 +15,7 @@ jobs:
         version:
           - '1.0'
           - '1'
-#          - 'nightly'
+          - 'nightly'
         os:
           - ubuntu-latest
           - macOS-latest

Project.toml

@@ -1,20 +1,27 @@
 name = "AbstractFFTs"
 uuid = "621f4979-c628-5d54-868e-fcf4e3e8185c"
-version = "1.2.1"
+version = "1.3.0"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 
+[weakdeps]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
+
+[extensions]
+AbstractFFTsChainRulesCoreExt = "ChainRulesCore"
+
 [compat]
 ChainRulesCore = "1"
 julia = "^1.0"
 
 [extras]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 ChainRulesTestUtils = "cdddcdb0-9152-4a09-a978-84456f9df70a"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 
 [targets]
-test = ["ChainRulesTestUtils", "Random", "Test", "Unitful"]
+test = ["ChainRulesCore", "ChainRulesTestUtils", "Random", "Test", "Unitful"]

src/chainrules.jl → ext/AbstractFFTsChainRulesCoreExt.jl

@@ -1,4 +1,8 @@
-# ffts
+module AbstractFFTsChainRulesCoreExt
+
+using AbstractFFTs
+import ChainRulesCore
+
 function ChainRulesCore.frule((_, Δx, _), ::typeof(fft), x::AbstractArray, dims)
     y = fft(x, dims)
     Δy = fft(Δx, dims)
@@ -46,7 +50,7 @@ function ChainRulesCore.frule((_, Δx, _), ::typeof(ifft), x::AbstractArray, dim
 end
 function ChainRulesCore.rrule(::typeof(ifft), x::AbstractArray, dims)
     y = ifft(x, dims)
-    invN = normalization(y, dims)
+    invN = AbstractFFTs.normalization(y, dims)
     project_x = ChainRulesCore.ProjectTo(x)
     function ifft_pullback(ȳ)
         x̄ = project_x(invN .* fft(ChainRulesCore.unthunk(ȳ), dims))
@@ -66,7 +70,7 @@ function ChainRulesCore.rrule(::typeof(irfft), x::AbstractArray, d::Int, dims)
     # compute scaling factors
     halfdim = first(dims)
     n = size(x, halfdim)
-    invN = normalization(y, dims)
+    invN = AbstractFFTs.normalization(y, dims)
     twoinvN = 2 * invN
     scale = reshape(
         [i == 1 || (i == n && 2 * (i - 1) == d) ? invN : twoinvN for i in 1:n],
@@ -150,3 +154,5 @@ function ChainRulesCore.rrule(::typeof(ifftshift), x::AbstractArray, dims)
     end
     return y, ifftshift_pullback
 end
+
+end # module

src/AbstractFFTs.jl

@@ -1,13 +1,14 @@
 module AbstractFFTs
 
-import ChainRulesCore
-
 export fft, ifft, bfft, fft!, ifft!, bfft!,
        plan_fft, plan_ifft, plan_bfft, plan_fft!, plan_ifft!, plan_bfft!,
        rfft, irfft, brfft, plan_rfft, plan_irfft, plan_brfft,
        fftdims, fftshift, ifftshift, fftshift!, ifftshift!, Frequencies, fftfreq, rfftfreq
 
 include("definitions.jl")
-include("chainrules.jl")
+
+if !isdefined(Base, :get_extension)
+    include("../ext/AbstractFFTsChainRulesCoreExt.jl")
+end
 
 end # module