fix: report all dependency failures instead of only the first

errors/errors.go

@@ -78,3 +78,8 @@ func AsType[T error](err error) (T, bool) {
 func Unwrap(err error) error {
 	return errors.Unwrap(err)
 }
+
+// Join wraps the standard errors.Join function so that we don't need to alias that package.
+func Join(errs ...error) error {
+	return errors.Join(errs...)
+}

task.go

@@ -309,15 +309,20 @@ func (e *Executor) mkdir(t *ast.Task) error {
 }
 
 func (e *Executor) runDeps(ctx context.Context, t *ast.Task) error {
+	failfast := e.Failfast || t.Failfast
 	g := &errgroup.Group{}
-	if e.Failfast || t.Failfast {
+	if failfast {
 		g, ctx = errgroup.WithContext(ctx)
 	}
 
 	reacquire := e.releaseConcurrencyLimit()
 	defer reacquire()
 
-	for _, d := range t.Deps {
+	// Without failfast every dep runs to completion, but errgroup.Wait only
+	// surfaces the first error, so all dep failures are collected and joined.
+	// Each dep writes its own slot, keeping the message in declaration order.
+	errs := make([]error, len(t.Deps))
+	for i, d := range t.Deps {
 		g.Go(func() error {
 			depCtx := ctx
 			var timeout *errors.TaskTimeoutError
@@ -330,13 +335,22 @@ func (e *Executor) runDeps(ctx context.Context, t *ast.Task) error {
 
 			err := e.RunTask(depCtx, &Call{Task: d.Task, Vars: d.Vars, Silent: d.Silent, Indirect: true})
 			if err != nil && timedOut(depCtx, timeout) {
-				return timeout
+				err = timeout
+			}
+			if !failfast && err != nil {
+				errs[i] = err
 			}
 			return err
 		})
 	}
 
-	return g.Wait()
+	if err := g.Wait(); err != nil {
+		if failfast {
+			return err
+		}
+		return errors.Join(errs...)
+	}
+	return nil
 }
 
 func (e *Executor) runDeferred(t *ast.Task, call *Call, i int, vars *ast.Vars, deferredExitCode *uint8) {

task_test.go

@@ -982,6 +982,29 @@ func TestCyclicDep(t *testing.T) {
 	assert.ErrorAs(t, err, &taskCalledTooManyTimesError)
 }
 
+func TestParallelDepsReportAllFailures(t *testing.T) {
+	t.Parallel()
+
+	const dir = "testdata/deps_fail"
+
+	e := task.NewExecutor(
+		task.WithDir(dir),
+		task.WithStdout(io.Discard),
+		task.WithStderr(io.Discard),
+	)
+	require.NoError(t, e.Setup())
+	err := e.Run(t.Context(), &task.Call{Task: "default"})
+	require.Error(t, err)
+	// Both failing deps must be surfaced, not just the first one, and in the
+	// order they are declared.
+	assert.Equal(t,
+		"task: Failed to run task \"default\": "+
+			"task: Failed to run task \"fail-1\": exit status 1\n"+
+			"task: Failed to run task \"fail-2\": exit status 1",
+		err.Error(),
+	)
+}
+
 func TestTaskVersion(t *testing.T) {
 	t.Parallel()
 

testdata/deps_fail/Taskfile.yml

@@ -0,0 +1,15 @@
+version: '3'
+
+tasks:
+  default:
+    deps: [fail-1, fail-2]
+    cmds:
+      - echo 'default'
+
+  fail-1:
+    cmds:
+      - exit 1
+
+  fail-2:
+    cmds:
+      - exit 1