Merge feature/1.13_errors_unwrap

Author: PeterIvanov

error.go

@@ -106,17 +106,9 @@ func (e *Error) HasTrait(key Trait) bool {
 // IsOfType is a proper type check for an errorx-based errors.
 // It takes the transparency and error types hierarchy into account,
 // so that type check against any supertype of the original cause passes.
+// Go 1.13 and above: it also tolerates non-errorx errors in chain if those errors support errors unwrap.
 func (e *Error) IsOfType(t *Type) bool {
-	cause := e
-	for cause != nil {
-		if !cause.transparent {
-			return cause.errorType.IsOfType(t)
-		}
-
-		cause = Cast(cause.Cause())
-	}
-
-	return false
+	return e.isOfType(t)
 }
 
 // Type returns the exact type of this error.

error_112.go

@@ -0,0 +1,23 @@
+// +build !go1.13
+
+package errorx
+
+func isOfType(err error, t *Type) bool {
+	e := Cast(err)
+	return e != nil && e.IsOfType(t)
+}
+
+func (e *Error) isOfType(t *Type) bool {
+	cause := e
+	for cause != nil {
+		if !cause.transparent {
+			return cause.errorType.IsOfType(t)
+		}
+
+		cause = Cast(cause.Cause())
+	}
+
+	return false
+}
+
+

error_113.go

@@ -0,0 +1,38 @@
+// +build go1.13
+
+package errorx
+
+import "errors"
+
+func isOfType(err error, t *Type) bool {
+	e := burrowForTyped(err)
+	return e != nil && e.IsOfType(t)
+}
+
+func (e *Error) isOfType(t *Type) bool {
+	cause := e
+	for cause != nil {
+		if !cause.transparent {
+			return cause.errorType.IsOfType(t)
+		}
+
+		cause = burrowForTyped(cause.Cause())
+	}
+
+	return false
+}
+
+// burrowForTyped returns either the first *Error in unwrap chain or nil
+func burrowForTyped(err error) *Error {
+	raw := err
+	for raw != nil {
+		typed := Cast(raw)
+		if typed != nil {
+			return typed
+		}
+
+		raw = errors.Unwrap(raw)
+	}
+
+	return nil
+}

error_113_test.go

@@ -4,6 +4,7 @@ package errorx
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"testing"
 
@@ -103,3 +104,28 @@ func TestErrorIs(t *testing.T) {
 		require.True(t, errors.Is(err, io.EOF))
 	})
 }
+
+func TestErrorsAndErrorx(t *testing.T) {
+	t.Run("DecoratedForeign", func(t *testing.T) {
+		err := fmt.Errorf("error test: %w", testType.NewWithNoMessage())
+		require.True(t, errors.Is(err, testType.NewWithNoMessage()))
+		require.True(t, IsOfType(err, testType))
+	})
+
+	t.Run("LayeredDecorate", func(t *testing.T) {
+		err := Decorate(fmt.Errorf("error test: %w", testType.NewWithNoMessage()), "test")
+		require.True(t, errors.Is(err, testType.NewWithNoMessage()))
+		require.True(t, IsOfType(err, testType))
+	})
+
+	t.Run("LayeredDecorateAgain", func(t *testing.T) {
+		err := fmt.Errorf("error test: %w", Decorate(io.EOF, "test"))
+		require.True(t, errors.Is(err, io.EOF))
+	})
+
+	t.Run("Wrap", func(t *testing.T) {
+		err := fmt.Errorf("error test: %w", testType.Wrap(io.EOF, "test"))
+		require.False(t, errors.Is(err, io.EOF))
+		require.True(t, errors.Is(err, testType.NewWithNoMessage()))
+	})
+}

type.go

@@ -97,10 +97,10 @@ func (t *Type) HasTrait(key Trait) bool {
 
 // IsOfType is a type check for errors.
 // Returns true either if both are of exactly the same type, or if the same is true for one of current type's ancestors.
-// For an error that does not have an errorx type, returns false.
+// Go 1.12 and below: for an error that does not have an errorx type, returns false.
+// Go 1.13 and above: for an error that does not have an errorx type, returns false unless it wraps another error of errorx type.
 func IsOfType(err error, t *Type) bool {
-	e := Cast(err)
-	return e != nil && e.IsOfType(t)
+	return isOfType(err, t)
 }
 
 // Supertype returns a parent type, if present.