From edda23923b43acad6863ed08d8f49206e165d4c7 Mon Sep 17 00:00:00 2001
From: Samuel Berthe <dev@samuel-berthe.fr>
Date: Sun, 2 Oct 2022 21:51:02 +0200
Subject: [PATCH] feat: adding ErrorsAs

---
 CHANGELOG.md   |  6 ++++++
 README.md      | 24 ++++++++++++++++++++++++
 errors.go      |  8 ++++++++
 errors_test.go | 24 ++++++++++++++++++++++++
 4 files changed, 62 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6bcd10f3..0ec57ad8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 @samber: I sometimes forget to update this file. Ping me on [Twitter](https://twitter.com/samuelberthe) or open an issue in case of error. We need to keep a clear changelog for easier lib upgrade.
 
+## 1.29.0 (2022-10-02)
+
+Adding:
+
+- lo.ErrorAs
+
 ## 1.28.0 (2022-09-05)
 
 Adding:
diff --git a/README.md b/README.md
index 7fec142e..cf06cee9 100644
--- a/README.md
+++ b/README.md
@@ -212,6 +212,7 @@ Error handling:
 - [TryCatch](#trycatch)
 - [TryWithErrorValue](#trywitherrorvalue)
 - [TryCatchWithErrorValue](#trycatchwitherrorvalue)
+- [ErrorsAs](#errorsas)
 
 Constraints:
 
@@ -2071,6 +2072,29 @@ ok := lo.TryCatchWithErrorValue(func() error {
 // caught == true
 ```
 
+### ErrorsAs
+
+A shortcut for:
+
+```go
+err := doSomething()
+
+var rateLimitErr *RateLimitError
+if ok := errors.As(err, &rateLimitErr); ok {
+    // retry later
+}
+```
+
+1 line `lo` helper:
+
+```go
+err := doSomething()
+
+if rateLimitErr, ok := lo.ErrorsAs[*RateLimitError](err); ok {
+    // retry later
+}
+```
+
 ## 🛩 Benchmark
 
 We executed a simple benchmark with the a dead-simple `lo.Map` loop:
diff --git a/errors.go b/errors.go
index e9f9c8e6..6427db18 100644
--- a/errors.go
+++ b/errors.go
@@ -1,6 +1,7 @@
 package lo
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 )
@@ -199,3 +200,10 @@ func TryCatchWithErrorValue(callback func() error, catch func(any)) {
 		catch(err)
 	}
 }
+
+// ErrorsAs is a shortcut for errors.As(err, &&T).
+func ErrorsAs[T error](err error) (T, bool) {
+	var t T
+	ok := errors.As(err, &t)
+	return t, ok
+}
diff --git a/errors_test.go b/errors_test.go
index df576108..976efe74 100644
--- a/errors_test.go
+++ b/errors_test.go
@@ -361,3 +361,27 @@ func TestTryCatchWithErrorValue(t *testing.T) {
 	})
 	is.False(caught)
 }
+
+type internalError struct {
+	foobar string
+}
+
+func (e *internalError) Error() string {
+	return fmt.Sprintf("internal error")
+}
+
+func TestErrorsAs(t *testing.T) {
+	is := assert.New(t)
+
+	err, ok := ErrorsAs[*internalError](fmt.Errorf("hello world"))
+	is.False(ok)
+	is.Nil(nil, err)
+
+	err, ok = ErrorsAs[*internalError](&internalError{foobar: "foobar"})
+	is.True(ok)
+	is.Equal(&internalError{foobar: "foobar"}, err)
+
+	err, ok = ErrorsAs[*internalError](nil)
+	is.False(ok)
+	is.Nil(nil, err)
+}