✨ Refactor: Convert WaitErr to an interface and add New constructor

README.md

@@ -33,7 +33,7 @@ import (
 )
 
 func main() {
-	we := new(waiterr.WaitErr)
+	we := waiterr.New()
 
 	we.Go(func() error {
 		time.Sleep(100 * time.Millisecond)
@@ -60,7 +60,7 @@ func main() {
 	}
 
 	// You can also get the first error immediately
-	we2 := new(waiterr.WaitErr)
+	we2 := waiterr.New()
 	we2.Go(func() error {
 		time.Sleep(100 * time.Millisecond)
 		return errors.New("first error from we2")

example_test.go

@@ -9,8 +9,7 @@ import (
 )
 
 func Example() {
-	we := new(waiterr.WaitErr)
-
+	we := waiterr.New()
 	we.Go(func() error {
 		time.Sleep(100 * time.Millisecond)
 		fmt.Println("Goroutine 1 finished")
@@ -43,7 +42,7 @@ func Example() {
 }
 
 func ExampleWaitErr_WaitForError() {
-	we := new(waiterr.WaitErr)
+	we := waiterr.New()
 	we.Go(func() error {
 		time.Sleep(100 * time.Millisecond)
 		return errors.New("first error from we")
@@ -63,7 +62,7 @@ func ExampleWaitErr_WaitForError() {
 }
 
 func ExampleWaitErr_Unwrap() {
-	we := new(waiterr.WaitErr)
+	we := waiterr.New()
 	we.Go(func() error {
 		time.Sleep(100 * time.Millisecond)
 		return errors.New("first error from we")

waiterr.go

@@ -5,23 +5,43 @@ import (
 	"sync"
 )
 
+func New() WaitErr {
+	var we waitErr
+	we.errCh = make(chan error, 1)
+
+	return &we
+}
+
+// WaitErr provides a way to run multiple goroutines and wait for their completion,
+// collecting any errors they return.
+type WaitErr interface {
+	// Go runs f in its own goroutine. When f returns, its error is stored, and returned
+	// with [WaitErr.Wait].
+	Go(f func() error)
+	// WaitForError waits for the first error to be returned by one of our go routines, and immediately returns
+	// with that error. If all functions return successfully, a nil is returned.
+	WaitForError() error
+	// Wait for all current goroutines to finish. Return an error that combines all errors returned
+	// in the group so far (if any).
+	Wait() error
+	// Unwrap returns all non-nil errors returned by our functions.
+	// If no errors were returned, or all errors are nil, it returns nil.
+	Unwrap() []error
+}
+
 // WaitErr wraps a [sync.WaitGroup] with error handling.
-type WaitErr struct {
-	wg            sync.WaitGroup
-	errs          []error
-	mut           sync.RWMutex
-	firstErr      error
-	firstErrOnce  sync.Once
-	errCh         chan error // Buffered channel of size 1
-	initErrChOnce sync.Once
+type waitErr struct {
+	wg           sync.WaitGroup
+	errs         []error
+	mut          sync.RWMutex
+	firstErr     error
+	firstErrOnce sync.Once
+	errCh        chan error // Buffered channel of size 1
 }
 
 // Go runs f in its own goroutine. When f returns, its error is stored, and returned
 // with [WaitErr.Wait].
-func (we *WaitErr) Go(f func() error) {
-	we.initErrChOnce.Do(func() {
-		we.errCh = make(chan error, 1)
-	})
+func (we *waitErr) Go(f func() error) {
 	wrap := func() {
 		err := f()
 
@@ -48,10 +68,7 @@ func (we *WaitErr) Go(f func() error) {
 
 // WaitForError waits for the first error to be returned by one of our go routines, and immediately returns
 // with that error. If all functions return successfully, a nil is returned. It will panic if called before Go.
-func (we *WaitErr) WaitForError() error {
-	if we.errCh == nil {
-		panic("WaitForError called before Go")
-	}
+func (we *waitErr) WaitForError() error {
 	// Check if an error has already been set
 	we.mut.RLock()
 	if we.firstErr != nil {
@@ -82,7 +99,7 @@ func (we *WaitErr) WaitForError() error {
 
 // Wait for all current goroutines to finish. Return an error that combines all errors returned
 // in the group so far (if any).
-func (we *WaitErr) Wait() error {
+func (we *waitErr) Wait() error {
 	we.wg.Wait()
 	we.mut.RLock()
 	defer we.mut.RUnlock()
@@ -91,7 +108,7 @@ func (we *WaitErr) Wait() error {
 
 // Unwrap returns all non-nil errors returned by our functions.
 // If no errors were returned, or all errors are nil, it returns nil.
-func (we *WaitErr) Unwrap() []error {
+func (we *waitErr) Unwrap() []error {
 	errs := make([]error, 0, len(we.errs))
 	for _, e := range we.errs {
 		if e != nil {

waiterr_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestGo(t *testing.T) {
-	we := new(waiterr.WaitErr)
+	we := waiterr.New()
 	err := errors.New("uh-oh")
 	var run bool
 	we.Go(func() error {
@@ -24,7 +24,7 @@ func TestGo(t *testing.T) {
 }
 
 func TestWait(t *testing.T) {
-	we := new(waiterr.WaitErr)
+	we := waiterr.New()
 	er1 := errors.New("uh-oh")
 	er2 := errors.New("oops")
 	we.Go(func() error { return er1 })
@@ -45,7 +45,7 @@ func TestWait(t *testing.T) {
 
 func TestWaitForError(tt *testing.T) {
 	tt.Run("first error", func(t *testing.T) {
-		we := new(waiterr.WaitErr)
+		we := waiterr.New()
 		er1 := errors.New("uh-oh")
 		er2 := errors.New("oops")
 		we.Go(func() error { return nil })
@@ -58,7 +58,7 @@ func TestWaitForError(tt *testing.T) {
 	})
 
 	tt.Run("no error", func(t *testing.T) {
-		we := new(waiterr.WaitErr)
+		we := waiterr.New()
 		we.Go(func() error { return nil })
 		we.Go(func() error { return nil })
 		we.Go(func() error { return nil })
@@ -67,19 +67,8 @@ func TestWaitForError(tt *testing.T) {
 		be.Err(t, err, nil)
 	})
 
-	tt.Run("panic", func(t *testing.T) {
-		defer func() {
-			if r := recover(); r == nil {
-				t.Errorf("The code did not panic")
-			}
-		}()
-
-		we := new(waiterr.WaitErr)
-		_ = we.WaitForError()
-	})
-
 	tt.Run("first error set", func(tt2 *testing.T) {
-		we := new(waiterr.WaitErr)
+		we := waiterr.New()
 		expectedErr := errors.New("pre-set error")
 
 		synctest.Test(tt2, func(t *testing.T) {
@@ -100,7 +89,7 @@ func TestWaitForError(tt *testing.T) {
 
 func TestUnwrap(tt *testing.T) {
 	tt.Run("two errors", func(t *testing.T) {
-		we := new(waiterr.WaitErr)
+		we := waiterr.New()
 		er1 := errors.New("error one")
 		er2 := errors.New("error two")
 
@@ -118,7 +107,7 @@ func TestUnwrap(tt *testing.T) {
 	})
 
 	tt.Run("no errors", func(t *testing.T) {
-		weNoErr := new(waiterr.WaitErr)
+		weNoErr := waiterr.New()
 		weNoErr.Go(func() error { return nil })
 		weNoErr.Go(func() error { return nil })
 		_ = weNoErr.Wait()