Add common error definitions

Signed-off-by: Christopher Crone <christopher.crone@docker.com>

errdefs/errors.go

@@ -0,0 +1,56 @@
+/*
+	Copyright (c) 2020 Docker Inc.
+
+	Permission is hereby granted, free of charge, to any person
+	obtaining a copy of this software and associated documentation
+	files (the "Software"), to deal in the Software without
+	restriction, including without limitation the rights to use, copy,
+	modify, merge, publish, distribute, sublicense, and/or sell copies
+	of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be
+	included in all copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+	EXPRESS OR IMPLIED,
+	INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+	IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+	HOLDERS BE LIABLE FOR ANY CLAIM,
+	DAMAGES OR OTHER LIABILITY,
+	WHETHER IN AN ACTION OF CONTRACT,
+	TORT OR OTHERWISE,
+	ARISING FROM, OUT OF OR IN CONNECTION WITH
+	THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+package errdefs
+
+import (
+	"github.com/pkg/errors"
+)
+
+var (
+	// ErrNotFound is returned when an object is not found
+	ErrNotFound = errors.New("not found")
+	// ErrAlreadyExists is returned when an object already exists
+	ErrAlreadyExists = errors.New("already exists")
+	// ErrUnknown is returned when the error type is unmapped
+	ErrUnknown = errors.New("unknown")
+)
+
+// IsNotFoundError returns true if the unwrapped error is ErrNotFound
+func IsNotFoundError(err error) bool {
+	return errors.Is(err, ErrNotFound)
+}
+
+// IsAlreadyExistsError returns true if the unwrapped error is ErrAlreadyExists
+func IsAlreadyExistsError(err error) bool {
+	return errors.Is(err, ErrAlreadyExists)
+}
+
+// IsUnknownError returns true if the unwrapped error is ErrUnknown
+func IsUnknownError(err error) bool {
+	return errors.Is(err, ErrUnknown)
+}

errdefs/errors_test.go

@@ -0,0 +1,49 @@
+/*
+	Copyright (c) 2020 Docker Inc.
+
+	Permission is hereby granted, free of charge, to any person
+	obtaining a copy of this software and associated documentation
+	files (the "Software"), to deal in the Software without
+	restriction, including without limitation the rights to use, copy,
+	modify, merge, publish, distribute, sublicense, and/or sell copies
+	of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be
+	included in all copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+	EXPRESS OR IMPLIED,
+	INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+	IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+	HOLDERS BE LIABLE FOR ANY CLAIM,
+	DAMAGES OR OTHER LIABILITY,
+	WHETHER IN AN ACTION OF CONTRACT,
+	TORT OR OTHERWISE,
+	ARISING FROM, OUT OF OR IN CONNECTION WITH
+	THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+package errdefs
+
+import (
+	"testing"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsNotFound(t *testing.T) {
+	err := errors.Wrap(ErrNotFound, `object "name"`)
+	require.True(t, IsNotFoundError(err))
+
+	require.False(t, IsNotFoundError(errors.New("another error")))
+}
+
+func TestIsAlreadyExists(t *testing.T) {
+	err := errors.Wrap(ErrAlreadyExists, `object "name"`)
+	require.True(t, IsAlreadyExistsError(err))
+
+	require.False(t, IsAlreadyExistsError(errors.New("another error")))
+}