feat!: add As, drop HasType and Split (#18)

Author: tmzane

README.md

@@ -22,30 +22,31 @@ go get go-simpler.org/errorsx
 A multi-target version of `errors.Is`.
 
 ```go
-if errorsx.IsAny(err, os.ErrNotExist, os.ErrPermission) {
+// Before:
+if errors.Is(err, os.ErrNotExist) || errors.Is(err, os.ErrPermission) {
     fmt.Println(err)
 }
-```
-
-### HasType
 
-Reports whether the error has type `T`.
-It is equivalent to `errors.As` without the need to declare the target variable.
-
-```go
-if errorsx.HasType[*os.PathError](err) {
+// After:
+if errorsx.IsAny(err, os.ErrNotExist, os.ErrPermission) {
     fmt.Println(err)
 }
 ```
 
-### Split
+### As
 
-Returns errors joined by `errors.Join` or by `fmt.Errorf` with multiple `%w` verbs.
-If the given error was created differently, `Split` returns nil.
+A generic version of `errors.As`.
 
 ```go
-if errs := errorsx.Split(err); errs != nil {
-    fmt.Println(errs)
+// Before:
+var pathErr *os.PathError
+if errors.As(err, &pathErr) {
+    fmt.Println(pathErr.Path)
+}
+
+// After:
+if pathErr, ok := errorsx.As[*os.PathError](err); ok {
+    fmt.Println(pathErr.Path)
 }
 ```
 
@@ -54,13 +55,16 @@ if errs := errorsx.Split(err); errs != nil {
 Attempts to close the given `io.Closer` and assigns the returned error (if any) to `err`.
 
 ```go
-func() (err error) {
-    f, err := os.Open("file.txt")
-    if err != nil {
-        return err
-    }
-    defer errorsx.Close(f, &err)
-
-    return nil
+f, err := os.Open("file.txt")
+if err != nil {
+    return err
+}
+
+// Before:
+defer func() {
+    err = errors.Join(err, f.Close())
 }()
+
+// After:
+defer errorsx.Close(f, &err)
 ```

errorsx.go

@@ -19,27 +19,15 @@ func IsAny(err, target error, targets ...error) bool {
 	return false
 }
 
-// HasType reports whether the error has type T.
-// It is equivalent to [errors.As] without the need to declare the target variable.
-func HasType[T any](err error) bool {
+// As is a generic version of [errors.As].
+func As[T any](err error) (T, bool) {
 	var t T
-	return errors.As(err, &t)
-}
-
-// Split returns errors joined by [errors.Join] or by [fmt.Errorf] with multiple %w verbs.
-// If the given error was created differently, Split returns nil.
-func Split(err error) []error {
-	u, ok := err.(interface{ Unwrap() []error })
-	if !ok {
-		return nil
-	}
-	return u.Unwrap()
+	ok := errors.As(err, &t)
+	return t, ok
 }
 
 // Close attempts to close the given [io.Closer] and assigns the returned error (if any) to err.
 // If err is already not nil, it will be joined with the [io.Closer]'s error.
 func Close(c io.Closer, err *error) { //nolint:gocritic // ptrToRefParam: err must be a pointer here.
-	if cerr := c.Close(); cerr != nil {
-		*err = errors.Join(*err, cerr)
-	}
+	*err = errors.Join(*err, c.Close())
 }

errorsx_test.go

@@ -3,7 +3,6 @@ package errorsx_test
 import (
 	"errors"
 	"fmt"
-	"slices"
 	"testing"
 
 	"go-simpler.org/errorsx"
@@ -30,16 +29,17 @@ func TestIsAny(t *testing.T) {
 	}
 }
 
-func TestHasType(t *testing.T) {
+func TestAs(t *testing.T) {
+	isok := func(_ any, ok bool) bool { return ok }
+
 	tests := map[string]struct {
 		fn   func(error) bool
 		err  error
 		want bool
 	}{
-		"no match":          {fn: errorsx.HasType[barError], err: errFoo, want: false},
-		"match (exact)":     {fn: errorsx.HasType[fooError], err: errFoo, want: true},
-		"match (wrapped)":   {fn: errorsx.HasType[fooError], err: wrap(errFoo), want: true},
-		"match (interface)": {fn: errorsx.HasType[interface{ Error() string }], err: errFoo, want: true},
+		"no match":        {fn: func(err error) bool { return isok(errorsx.As[barError](err)) }, err: errFoo, want: false},
+		"match (exact)":   {fn: func(err error) bool { return isok(errorsx.As[fooError](err)) }, err: errFoo, want: true},
+		"match (wrapped)": {fn: func(err error) bool { return isok(errorsx.As[fooError](err)) }, err: wrap(errFoo), want: true},
 	}
 
 	for name, test := range tests {
@@ -51,26 +51,6 @@ func TestHasType(t *testing.T) {
 	}
 }
 
-func TestSplit(t *testing.T) {
-	tests := map[string]struct {
-		err      error
-		wantErrs []error
-	}{
-		"nil error":                   {err: nil, wantErrs: nil},
-		"single error":                {err: errFoo, wantErrs: nil},
-		"joined errors (errors.Join)": {err: errors.Join(errFoo, errBar), wantErrs: []error{errFoo, errBar}},
-		"joined errors (fmt.Errorf)":  {err: fmt.Errorf("%w; %w", errFoo, errBar), wantErrs: []error{errFoo, errBar}},
-	}
-
-	for name, test := range tests {
-		t.Run(name, func(t *testing.T) {
-			if gotErrs := errorsx.Split(test.err); !slices.Equal(gotErrs, test.wantErrs) {
-				t.Errorf("got %v; want %v", gotErrs, test.wantErrs)
-			}
-		})
-	}
-}
-
 func TestClose(t *testing.T) {
 	tests := map[string]struct {
 		mainErr  error
@@ -112,8 +92,8 @@ type barError struct{}
 
 func (barError) Error() string { return "bar" }
 
-func wrap(err error) error { return fmt.Errorf("%w", err) }
-
 type errCloser struct{ err error }
 
 func (c *errCloser) Close() error { return c.err }
+
+func wrap(err error) error { return fmt.Errorf("%w", err) }

example_test.go

@@ -15,27 +15,20 @@ func ExampleIsAny() {
 	}
 }
 
-func ExampleHasType() {
-	if errorsx.HasType[*os.PathError](err) {
-		fmt.Println(err)
+func ExampleAs() {
+	if pathErr, ok := errorsx.As[*os.PathError](err); ok {
+		fmt.Println(pathErr.Path)
 	}
 }
 
-func ExampleSplit() {
-	if errs := errorsx.Split(err); errs != nil {
-		fmt.Println(errs)
-	}
-}
-
-//nolint:errcheck // this is just an example.
 func ExampleClose() {
-	func() (err error) {
+	_ = func() (err error) {
 		f, err := os.Open("file.txt")
 		if err != nil {
 			return err
 		}
 		defer errorsx.Close(f, &err)
 
 		return nil
-	}()
+	}
 }