Avoid Runtime Checks for Zygote Being loaded

.JuliaFormatter.toml

@@ -1,3 +1,4 @@
 style = "sciml"
 format_markdown = true
 annotate_untyped_fields_with_any = false
+format_docstrings = true

Project.toml

@@ -30,11 +30,13 @@ UnPack = "3a884ed6-31ef-47d7-9d2a-63182c4928ed"
 BandedMatrices = "aae01518-5342-5314-be14-df237901396f"
 FastLevenbergMarquardt = "7a0df574-e128-4d35-8cbd-3d84502bf7ce"
 LeastSquaresOptim = "0fc2ff8b-aaa3-5acd-a817-1944a5e08891"
+Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [extensions]
 NonlinearSolveBandedMatricesExt = "BandedMatrices"
 NonlinearSolveFastLevenbergMarquardtExt = "FastLevenbergMarquardt"
 NonlinearSolveLeastSquaresOptimExt = "LeastSquaresOptim"
+NonlinearSolveZygoteExt = "Zygote"
 
 [compat]
 ADTypes = "0.2"

ext/NonlinearSolveZygoteExt.jl

@@ -0,0 +1,7 @@
+module NonlinearSolveZygoteExt
+
+import NonlinearSolve, Zygote
+
+NonlinearSolve.is_extension_loaded(::Val{:Zygote}) = true
+
+end

src/NonlinearSolve.jl

@@ -38,6 +38,9 @@ import DiffEqBase: AbstractNonlinearTerminationMode,
 const AbstractSparseADType = Union{ADTypes.AbstractSparseFiniteDifferences,
     ADTypes.AbstractSparseForwardMode, ADTypes.AbstractSparseReverseMode}
 
+# Type-Inference Friendly Check for Extension Loading
+is_extension_loaded(::Val) = false
+
 abstract type AbstractNonlinearSolveLineSearchAlgorithm end
 
 abstract type AbstractNonlinearSolveAlgorithm <: AbstractNonlinearAlgorithm end

src/extension_algs.jl

@@ -8,13 +8,15 @@ for solving `NonlinearLeastSquaresProblem`.
 
 ## Arguments:
 
-- `alg`: Algorithm to use. Can be `:lm` or `:dogleg`.
-- `linsolve`: Linear solver to use. Can be `:qr`, `:cholesky` or `:lsmr`. If
-  `nothing`, then `LeastSquaresOptim.jl` will choose the best linear solver based
-  on the Jacobian structure.
-- `autodiff`: Automatic differentiation / Finite Differences. Can be `:central` or `:forward`.
+  - `alg`: Algorithm to use. Can be `:lm` or `:dogleg`.
+  - `linsolve`: Linear solver to use. Can be `:qr`, `:cholesky` or `:lsmr`. If `nothing`,
+    then `LeastSquaresOptim.jl` will choose the best linear solver based on the Jacobian
+    structure.
+  - `autodiff`: Automatic differentiation / Finite Differences. Can be `:central` or
+    `:forward`.
 
 !!! note
+
     This algorithm is only available if `LeastSquaresOptim.jl` is installed.
 """
 struct LeastSquaresOptimJL{alg, linsolve} <: AbstractNonlinearSolveAlgorithm
@@ -36,21 +38,24 @@ end
 """
     FastLevenbergMarquardtJL(linsolve = :cholesky)
 
-Wrapper over [FastLevenbergMarquardt.jl](https://github.com/kamesy/FastLevenbergMarquardt.jl) for solving
-`NonlinearLeastSquaresProblem`.
+Wrapper over [FastLevenbergMarquardt.jl](https://github.com/kamesy/FastLevenbergMarquardt.jl)
+for solving `NonlinearLeastSquaresProblem`.
 
 !!! warning
+
     This is not really the fastest solver. It is called that since the original package
     is called "Fast". `LevenbergMarquardt()` is almost always a better choice.
 
 !!! warning
+
     This algorithm requires the jacobian function to be provided!
 
 ## Arguments:
 
-- `linsolve`: Linear solver to use. Can be `:qr` or `:cholesky`.
+  - `linsolve`: Linear solver to use. Can be `:qr` or `:cholesky`.
 
 !!! note
+
     This algorithm is only available if `FastLevenbergMarquardt.jl` is installed.
 """
 @concrete struct FastLevenbergMarquardtJL{linsolve} <: AbstractNonlinearSolveAlgorithm

src/jacobian.jl

@@ -166,12 +166,8 @@ function __concrete_vjp_autodiff(vjp_autodiff, jvp_autodiff, uf)
             # Short circuit if we see that FiniteDiff was used for J computation
             jvp_autodiff isa AutoFiniteDiff && return jvp_autodiff
             # Check if Zygote is loaded then use Zygote else use FiniteDiff
-            if haskey(Base.loaded_modules,
-                Base.PkgId(Base.UUID("e88e6eb3-aa80-5325-afca-941959d7151f"), "Zygote"))
-                return AutoZygote()
-            else
-                return AutoFiniteDiff()
-            end
+            is_extension_loaded(Val{:Zygote}()) && return AutoZygote()
+            return AutoFiniteDiff()
         end
     else
         ad = __get_nonsparse_ad(vjp_autodiff)

src/linesearch.jl

@@ -114,8 +114,7 @@ function LineSearchesJLCache(ls::LineSearch, f::F, u, p, fu1, IIP::Val{iip}) whe
     g₀ = _mutable_zero(u)
 
     autodiff = if ls.autodiff === nothing
-        if !iip && haskey(Base.loaded_modules,
-            Base.PkgId(Base.UUID("e88e6eb3-aa80-5325-afca-941959d7151f"), "Zygote"))
+        if !iip && is_extension_loaded(Val{:Zygote}())
             AutoZygote()
         else
             AutoFiniteDiff()

src/pseudotransient.jl

@@ -12,6 +12,7 @@ the time-stepping and algorithm, please see the paper:
 SIAM Journal on Scientific Computing,25, 553-569.](https://doi.org/10.1137/S106482750241044X)
 
 ### Keyword Arguments
+
   - `autodiff`: determines the backend used for the Jacobian. Note that this argument is
     ignored if an analytical Jacobian is passed, as that will be used instead. Defaults to
     `nothing` which means that a default is selected according to the problem specification!

src/utils.jl

@@ -23,6 +23,7 @@ Construct the AD type from the arguments. This is mostly needed for compatibilit
 code.
 
 !!! warning
+
     `chunk_size`, `standardtag`, `diff_type`, and `autodiff::Union{Val, Bool}` are
     deprecated and will be removed in v3. Update your code to directly specify
     `autodiff=<ADTypes>`.