From 06cab9921d64d96cd2d431a8629eefb20befe483 Mon Sep 17 00:00:00 2001
From: Pavel <pashok9825@gmail.com>
Date: Wed, 30 Oct 2019 17:02:11 +0300
Subject: [PATCH] error collector (mostly for migrations)

---
 core/error_collector.go      | 38 ++++++++++++++++++++++++++++++++++
 core/error_collector_test.go | 40 ++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 core/error_collector.go
 create mode 100644 core/error_collector_test.go

diff --git a/core/error_collector.go b/core/error_collector.go
new file mode 100644
index 0000000..f494ebb
--- /dev/null
+++ b/core/error_collector.go
@@ -0,0 +1,38 @@
+package core
+
+import (
+	"github.com/pkg/errors"
+)
+
+// ErrorCollector can be used to group several error calls into one call.
+// It is mostly useful in GORM migrations, where you should return only one errors, but several can occur.
+// Error messages are composed into one message. For example:
+// 		err := core.ErrorCollector(
+// 			errors.New("first"),
+// 			errors.New("second")
+// 		)
+//
+// 		// Will output `first < second`
+// 		fmt.Println(err.Error())
+// Example with GORM migration, returns one migration error with all error messages:
+// 		return core.ErrorCollector(
+// 			db.CreateTable(models.Account{}, models.Connection{}).Error,
+// 			db.Table("account").AddUniqueIndex("account_key", "channel").Error,
+// 		)
+func ErrorCollector(errorsList ...error) error {
+	var errorMsg string
+
+	for _, errItem := range errorsList {
+		if errItem == nil {
+			continue
+		}
+
+		errorMsg += "< " + errItem.Error() + " "
+	}
+
+	if errorMsg != "" {
+		return errors.New(errorMsg[2 : len(errorMsg)-1])
+	}
+
+	return nil
+}
diff --git a/core/error_collector_test.go b/core/error_collector_test.go
new file mode 100644
index 0000000..5eaf6ea
--- /dev/null
+++ b/core/error_collector_test.go
@@ -0,0 +1,40 @@
+package core
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestErrorCollector_NoError(t *testing.T) {
+	err := ErrorCollector(nil, nil, nil)
+
+	assert.NoError(t, err)
+	assert.Nil(t, err)
+}
+
+func TestErrorCollector_SeveralErrors(t *testing.T) {
+	err := ErrorCollector(nil, errors.New("error text"), nil)
+
+	assert.Error(t, err)
+	assert.Equal(t, "error text", err.Error())
+}
+
+func TestErrorCollector_EmptyErrorMessage(t *testing.T) {
+	err := ErrorCollector(nil, errors.New(""), nil)
+
+	assert.Error(t, err)
+	assert.Equal(t, "", err.Error())
+}
+
+func TestErrorCollector_AllErrors(t *testing.T) {
+	err := ErrorCollector(
+		errors.New("first"),
+		errors.New("second"),
+		errors.New("third"),
+	)
+
+	assert.Error(t, err)
+	assert.Equal(t, "first < second < third", err.Error())
+}