feat: add JoinErrors (#5)

Author: tmzane

README.md

@@ -16,12 +16,12 @@ go get go-simpler.org/check
 ## 📋 Usage
 
 Use `That`/`Thatf` to write conditions to check, multiple calls can be chained.
-The last call in the chain must be either `FirstError` or `AllErrors`.
+The last call in the chain must be `FirstError`, `AllErrors`, or `JoinErrors`.
 
 ```go
-errs := check.
+err := check.
     That(user.Name != "", errEmptyName).
     Thatf(user.Age >= 18, "%d y.o. is too young", user.Age).
     Thatf(isEmail(user.Email), "%s is invalid email", user.Email).
-    AllErrors() // OR FirstError() to check only the first error.
+    JoinErrors() // or FirstError() / AllErrors().
 ```

check.go

@@ -1,10 +1,13 @@
 // Package check provides convenience helpers to perform validations of any kind.
 //
-// Use That/Thatf to write conditions to check, multiple calls can be chained.
-// The last call in the chain must be either FirstError or AllErrors.
+// Use [That]/[Thatf] to write conditions to check, multiple calls can be chained.
+// The last call in the chain must be FirstError, AllErrors, or JoinErrors.
 package check
 
-import "fmt"
+import (
+	"errors"
+	"fmt"
+)
 
 // That checks whether the condition is true, and if not, records the error.
 func That(cond bool, err error) *State {
@@ -16,7 +19,7 @@ func Thatf(cond bool, format string, args ...any) *State {
 	return new(State).Thatf(cond, format, args...)
 }
 
-// State holds the errors of the failed conditions.
+// State holds the recorded errors.
 // It is exported only for the purpose of documentation.
 type State struct {
 	errs []error
@@ -38,13 +41,16 @@ func (s *State) Thatf(cond bool, format string, args ...any) *State {
 	return s.That(cond, fmt.Errorf(format, args...))
 }
 
-// FirstError returns the error of the first failed condition.
+// FirstError returns the first recorded error.
 func (s *State) FirstError() error {
 	if len(s.errs) > 0 {
 		return s.errs[0]
 	}
 	return nil
 }
 
-// AllErrors returns the errors of all failed conditions.
+// AllErrors returns all the recorded errors.
 func (s *State) AllErrors() []error { return s.errs }
+
+// JoinErrors returns all the recorded errors joined via [errors.Join].
+func (s *State) JoinErrors() error { return errors.Join(s.errs...) }

check_test.go

@@ -8,35 +8,43 @@ import (
 )
 
 func TestCheck(t *testing.T) {
-	t.Run("first error", func(t *testing.T) {
-		err12 := errors.New("1 and 2 are not equal")
-		err34 := errors.New("3 and 4 are not equal")
+	err12 := errors.New("1 and 2 are not equal")
+	err34 := errors.New("3 and 4 are not equal")
 
-		err := check.
-			That(1 == 2, err12).
-			That(3 == 4, err34).
-			FirstError()
+	state := check.
+		That(1 == 2, err12).
+		That(3 == 4, err34)
+
+	t.Run("first error", func(t *testing.T) {
+		err := state.FirstError()
 
 		if !errors.Is(err, err12) {
 			t.Errorf("got %v; want %v", err, err12)
 		}
 	})
 
 	t.Run("all errors", func(t *testing.T) {
-		errs := check.
-			Thatf("foo" == "baz", "foo and bar are not equal").
-			Thatf(true == false, "true and false are not equal").
-			AllErrors()
+		errs := state.AllErrors()
 
 		if len(errs) != 2 {
 			t.Fatalf("want 2 errors")
 		}
-
 		if errs[0] == nil || errs[1] == nil {
 			t.Errorf("want all errors to be non-nil")
 		}
 	})
 
+	t.Run("join errors", func(t *testing.T) {
+		err := state.JoinErrors()
+
+		if !errors.Is(err, err12) {
+			t.Errorf("got %v; want %v", err, err12)
+		}
+		if !errors.Is(err, err34) {
+			t.Errorf("got %v; want %v", err, err34)
+		}
+	})
+
 	t.Run("panic on nil error", func(t *testing.T) {
 		defer func() {
 			if r := recover(); r == nil {

example_test.go

@@ -22,16 +22,13 @@ func isEmail(string) bool { return false }
 var errEmptyName = errors.New("name must not be empty")
 
 func Example() {
-	errs := check.
+	err := check.
 		That(user.Name != "", errEmptyName).
 		Thatf(user.Age >= 18, "%d y.o. is too young", user.Age).
 		Thatf(isEmail(user.Email), "%s is invalid email", user.Email).
-		AllErrors() // OR FirstError() to check only the first error.
-
-	for _, err := range errs {
-		fmt.Println(err)
-	}
+		JoinErrors() // or FirstError() / AllErrors().
 
+	fmt.Println(err)
 	// Output:
 	// name must not be empty
 	// 10 y.o. is too young