Add Identity function

README.md

@@ -228,6 +228,7 @@ Type manipulation helpers:
 - [IsEmpty](#isempty)
 - [IsNotEmpty](#isnotempty)
 - [Coalesce](#coalesce)
+- [Identity](#identity)
 
 Function helpers:
 
@@ -2344,6 +2345,17 @@ result, ok := lo.Coalesce[*string](nil, nilStr, &str)
 // &"foobar" true
 ```
 
+### Identity
+
+Returns the argument itself.
+```go
+lo.Identity(42)
+// 42
+
+lo.Identity("foobar")
+// "foobar"
+```
+
 ### Partial
 
 Returns new function that, when called, has its first argument set to the provided value.

type_manipulation.go

@@ -106,3 +106,8 @@ func Coalesce[T comparable](v ...T) (result T, ok bool) {
 
 	return
 }
+
+// Identity returns the argument itself.
+func Identity[T any](v T) T {
+	return v
+}

type_manipulation_test.go

@@ -233,3 +233,23 @@ func TestCoalesce(t *testing.T) {
 	is.Equal(result10, struct1)
 	is.True(ok10)
 }
+
+func TestIdentity(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	is.Equal(Identity[int](42), 42)
+	is.Equal(Identity[string]("foobar"), "foobar")
+	is.Equal(Identity[bool](true), true)
+	is.Equal(Identity[bool](false), false)
+	is.Equal(Identity[error](assert.AnError), assert.AnError)
+	is.Equal(Identity[interface{}]("foobar"), "foobar")
+	is.Equal(Identity[interface{}](42), 42)
+	is.Equal(Identity[interface{}](true), true)
+	is.Equal(Identity[interface{}](false), false)
+	is.Equal(Identity[interface{}](assert.AnError), assert.AnError)
+	is.Equal(Identity[interface{}](nil), nil)
+	is.Equal(Identity[interface{}]([]int{1, 2, 3}), []int{1, 2, 3})
+	is.Equal(Identity[interface{}](map[int]string{1: "foo", 2: "bar"}), map[int]string{1: "foo", 2: "bar"})
+	is.Equal(Identity[interface{}](struct{ foo string }{foo: "bar"}), struct{ foo string }{foo: "bar"})
+}