Add function Validate that creates an error when a condition is not m…

…et (#221)

README.md

@@ -208,6 +208,7 @@ Concurrency helpers:
 
 Error handling:
 
+- [Validate](#validate)
 - [Must](#must)
 - [Try](#try)
 - [Try1 -> Try6](#try0-6)
@@ -2079,6 +2080,21 @@ ch := lo.Async2(func() (int, string) {
 // chan lo.Tuple2[int, string] ({42, "Hello"})
 ```
 
+### Validate
+
+Helper function that creates an error when a condition is not met.
+
+```go
+slice := []string{"a"}
+val := lo.Validate(len(slice) == 0, "Slice should be empty but contains %v", slice)
+// error("Slice should be empty but contains [a]")
+
+slice := []string{}
+val := lo.Validate(len(slice) == 0, "Slice should be empty but contains %v", slice)
+// nil
+```
+
+
 ### Must
 
 Wraps a function call to panics if second argument is `error` or `false`, returns the value otherwise.

errors.go

@@ -6,6 +6,14 @@ import (
 	"reflect"
 )
 
+// Validate is a helper that creates an error when a condition is not met.
+func Validate(ok bool, format string, args ...any) error {
+	if !ok {
+		return errors.New(fmt.Sprint(format, args))
+	}
+	return nil
+}
+
 func messageFromMsgAndArgs(msgAndArgs ...interface{}) string {
 	if len(msgAndArgs) == 1 {
 		if msgAsStr, ok := msgAndArgs[0].(string); ok {

errors_test.go

@@ -8,6 +8,19 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestValidate(t *testing.T) {
+	is := assert.New(t)
+
+	slice := []string{"a"}
+	result1 := Validate(len(slice) == 0, "Slice should be empty but contains %v", slice)
+
+	slice = []string{}
+	result2 := Validate(len(slice) == 0, "Slice should be empty but contains %v", slice)
+
+	is.Error(result1)
+	is.NoError(result2)
+}
+
 func TestMust(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)