Merge pull request #19 from ccremer/errorhandler

Add error handler

step.go

@@ -21,3 +21,15 @@ func (s Step) WithResultHandler(handler ResultHandler) Step {
 	s.H = handler
 	return s
 }
+
+// WithErrorHandler wraps given errorHandler and sets the ResultHandler of this specific step and returns the step itself.
+// The difference to WithResultHandler is that errorHandler only gets called if Result.Err is non-nil.
+func (s Step) WithErrorHandler(errorHandler func(ctx Context, err error) error) Step {
+	s.H = func(ctx Context, result Result) error {
+		if result.IsFailed() {
+			return errorHandler(ctx, result.Err)
+		}
+		return nil
+	}
+	return s
+}

step_test.go

@@ -0,0 +1,38 @@
+package pipeline
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestStep_WithErrorHandler(t *testing.T) {
+	tests := map[string]struct {
+		givenError        error
+		expectedExecution bool
+	}{
+		"GivenHandler_WhenErrorIsNil_ThenDoNotRunHandler": {
+			givenError:        nil,
+			expectedExecution: false,
+		},
+		"GivenHandler_WhenErrorGiven_ThenExecuteHandler": {
+			givenError:        errors.New("error"),
+			expectedExecution: true,
+		},
+	}
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			executed := false
+			s := NewStepFromFunc("test", func(_ Context) error {
+				return nil
+			}).WithErrorHandler(func(_ Context, err error) error {
+				executed = true
+				return err
+			})
+			err := s.H(nil, Result{Err: tt.givenError})
+			assert.Equal(t, tt.givenError, err)
+			assert.Equal(t, tt.expectedExecution, executed)
+		})
+	}
+}