Merge remote-tracking branch 'origin/main'

README.md

@@ -4,7 +4,7 @@
 
 ## About
 
-Here's [Go](https://go.dev) package for wrapping, chaining or combining multiple errors for further use with the standard `errors.Is`. You can learn more about working with errors in Go in [this](https://go.dev/blog/go1.13-errors) article. Explore the [example](#example) below for more understanding.
+Here's [Go](https://go.dev) package for errors chaining for further examining using the standard `errors.Is`. You can learn more about working with errors in Go in [this](https://go.dev/blog/go1.13-errors) article. Explore [example](#examples) below for more understanding.
 
 This package uses [module version numbering](https://go.dev/doc/modules/version-numbers).
 
@@ -16,9 +16,9 @@ With a [correctly configured](https://golang.org/doc/install#testing) Go toolcha
 go get github.com/electrofocus/errchain
 ```
 
-## Example
+## Examples
 
-Let's build new error from multiple errors:
+Let's build new error from multiple errors and examine it with `errors.Is`:
 
 ```go
 package main

errchain.go

@@ -46,3 +46,9 @@ func (c chain) Error() string {
 func (c chain) Is(target error) bool {
 	return errors.Is(c.error, target) || errors.Is(c.next, target)
 }
+
+// As finds the first error in chain that matches target, and if one is found, sets
+// target to that error value and returns true. Otherwise, it returns false.
+func (c chain) As(target any) bool {
+	return errors.As(c.error, target) || errors.As(c.next, target)
+}

errchain_test.go

@@ -1,8 +1,10 @@
 package errchain_test
 
 import (
+	"encoding/json"
 	"errors"
 	"io"
+	"io/fs"
 	"net/http"
 	"os"
 	"testing"
@@ -101,3 +103,43 @@ func TestIs(t *testing.T) {
 		t.Fatalf("unexpected result TRUE for error %s and %s", err, e)
 	}
 }
+
+type customErr struct {
+	text string
+}
+
+func (e customErr) Error() string {
+	return e.text
+}
+
+func TestAs(t *testing.T) {
+
+	err := errchain.New(
+		customErr{"first error text"},
+		&fs.PathError{Op: "readdir", Path: "home", Err: errors.New("not implemented")},
+		&json.SyntaxError{},
+	)
+
+	var (
+		err1 customErr
+		err2 *fs.PathError
+		err3 *json.SyntaxError
+		err4 *json.MarshalerError
+	)
+
+	if !errors.As(err, &err1) {
+		t.Fatalf("unexpected result FALSE for error %s and error type %T", err, err1)
+	}
+
+	if !errors.As(err, &err2) {
+		t.Fatalf("unexpected result FALSE for error %s and error type %T", err, err2)
+	}
+
+	if !errors.As(err, &err3) {
+		t.Fatalf("unexpected result FALSE for error %s and error type %T", err, err3)
+	}
+
+	if errors.As(err, &err4) {
+		t.Fatalf("unexpected result TRUE for error %s and error type %T", err, err4)
+	}
+}