add nothing as a noop correction strategy

Project.toml

@@ -1,7 +1,7 @@
 name = "MatrixCorrectionTools"
 uuid = "41f81499-25de-46de-b591-c3cfc21e9eaf"
 authors = ["Bagaev Dmitry <[email protected]>"]
-version = "1.1.0"
+version = "1.2.0"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/MatrixCorrectionTools.jl

@@ -13,9 +13,12 @@ abstract type AbstractCorrectionStrategy end
 Modifies the `input` in-place using a specified correction strategy.
 The `input` can be either a matrix or a number. 
 Certain strategies may require the input to satisfy specific properties beforehand, e.g., the input must be a square matrix.
+The `nothing` is a special correction strategy that does nothing and simply returns its input.
 """
 function correction! end
 
+correction!(::Nothing, input) = input
+
 """
     correction(strategy, input)
 

test/runtests.jl

@@ -28,6 +28,18 @@ MatrixCorrectionTools.correction!(::CustomStrategyAddsOneWithAbstractType, input
 
     end
 
+    @testset "`nothing` strategy" begin
+
+        @test correction!(nothing, 0) === 0
+
+        for n in (3, 4, 5)
+            local A = rand(n, n)
+            @test correction!(nothing, A) == deepcopy(A)
+            @test correction!(nothing, A) === A
+        end
+
+    end
+
     @testset "`NoCorrection` strategy" begin
         import MatrixCorrectionTools: NoCorrection