tests for errors.As

Author: PeterIvanov

error_113.go

@@ -2,7 +2,14 @@
 
 package errorx
 
+import "reflect"
+
 // todo godoc
+// NB: Call to errors.As() converts any type of errorx error to any other type, therefore such calls may break semantics.
+// Note than calls to errors.Is() do not suffer from the same issue.
+// todo add errorx.As() ?
+// todo make another type for passing into errors.As()?
+// todo when fixed, add tests for wrap/decorate etc.
 func (e *Error) As(target interface{}) bool {
 	targetError, ok := target.(*error)
 	if !ok {
@@ -13,7 +20,8 @@ func (e *Error) As(target interface{}) bool {
 		return false
 	}
 
-	// todo inject
+	targetVal := reflect.ValueOf(target)
+	targetVal.Elem().Set(reflect.ValueOf(e))
 	return true
 }
 
@@ -24,7 +32,7 @@ func (e *Error) Is(target error) bool {
 		return false
 	}
 
-	return e.IsOfType(typedTarget.Type()) // todo test with parents
+	return e.IsOfType(typedTarget.Type())
 }
 
 // todo godoc

error_113_test.go

@@ -4,6 +4,7 @@ package errorx
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"testing"
 
@@ -100,4 +101,48 @@ func TestErrorIs(t *testing.T) {
 		err := Decorate(io.EOF,"")
 		require.True(t, errors.Is(err, io.EOF))
 	})
+}
+
+func TestErrorAs(t *testing.T) {
+	t.Run("Trivial", func(t *testing.T) {
+		err := fooReturnsError()
+		target := testType.NewWithNoMessage()
+		require.True(t, errors.As(err, &target))
+		require.EqualValues(t, "whoops", target.Message())
+		output := fmt.Sprintf("%+v", target)
+		require.Contains(t, output, "fooReturnsError", output)
+	})
+
+	// Current errors.As allows no customization in this behaviour; if go types are assignable, here we go
+	t.Run("NegativeBroken", func(t *testing.T) {
+		err := fooReturnsError()
+		target := testTypeBar1.NewWithNoMessage()
+		require.True(t, errors.As(err, &target))
+		require.EqualValues(t, "whoops", target.Message())
+		require.True(t, IsOfType(target, testType))
+		require.False(t, IsOfType(target, testTypeBar1))
+	})
+
+	t.Run("Negative", func(t *testing.T) {
+		err := io.EOF
+		target := testTypeBar1.NewWithNoMessage()
+		require.False(t, errors.As(err, &target))
+	})
+
+	t.Run("DecorateForeign", func(t *testing.T) {
+		err := Decorate(myErr("test"),"")
+		var target myErr
+		require.True(t, errors.As(err, &target))
+		require.EqualValues(t, "test", target.Error())
+	})
+}
+
+func fooReturnsError() error {
+	return testType.New("whoops")
+}
+
+type myErr string
+
+func (e myErr) Error() string {
+	return string(e)
 }