allow error message on op defintions to show better error messages

Author: dmitriy kalinin

patch/descriptive_op.go

@@ -0,0 +1,18 @@
+package patch
+
+import (
+	"fmt"
+)
+
+type DescriptiveOp struct {
+	Op       Op
+	ErrorMsg string
+}
+
+func (op DescriptiveOp) Apply(doc interface{}) (interface{}, error) {
+	doc, err := op.Op.Apply(doc)
+	if err != nil {
+		return nil, fmt.Errorf("Error '%s': %s", op.ErrorMsg, err.Error())
+	}
+	return doc, nil
+}

patch/integration_test.go

@@ -159,4 +159,36 @@ jobs:
 
 		Expect(res).To(Equal(out))
 	})
+
+	It("shows custom error messages", func() {
+		inStr := `
+releases:
+- name: capi
+  version: 0.1
+`
+
+		var in interface{}
+
+		err := yaml.Unmarshal([]byte(inStr), &in)
+		Expect(err).ToNot(HaveOccurred())
+
+		opsStr := `
+- type: remove
+  path: /releases/0/not-there
+  error: "Custom error message"
+`
+
+		var opDefs []OpDefinition
+
+		err = yaml.Unmarshal([]byte(opsStr), &opDefs)
+		Expect(err).ToNot(HaveOccurred())
+
+		ops, err := NewOpsFromDefinitions(opDefs)
+		Expect(err).ToNot(HaveOccurred())
+
+		_, err = ops.Apply(in)
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(Equal(
+			"Error 'Custom error message': Expected to find a map key 'not-there' for path '/releases/0/not-there' (found map keys: 'name', 'version')"))
+	})
 })

patch/op_definition.go

@@ -11,6 +11,8 @@ type OpDefinition struct {
 	Type  string       `json:",omitempty"`
 	Path  *string      `json:",omitempty"`
 	Value *interface{} `json:",omitempty"`
+
+	Error *string `json:",omitempty"`
 }
 
 type parser struct{}
@@ -42,6 +44,10 @@ func NewOpsFromDefinitions(opDefs []OpDefinition) (Ops, error) {
 			return nil, fmt.Errorf("Unknown operation [%d] with type '%s' within\n%s", i, opDef.Type, opFmt)
 		}
 
+		if opDef.Error != nil {
+			op = DescriptiveOp{Op: op, ErrorMsg: *opDef.Error}
+		}
+
 		ops = append(ops, op)
 	}
 

patch/op_definition_test.go

@@ -11,6 +11,7 @@ var _ = Describe("NewOpsFromDefinitions", func() {
 	var (
 		path                    = "/abc"
 		invalidPath             = "abc"
+		errorMsg                = "error"
 		val         interface{} = 123
 		complexVal  interface{} = map[interface{}]interface{}{123: 123}
 	)
@@ -57,6 +58,20 @@ var _ = Describe("NewOpsFromDefinitions", func() {
 	})
 
 	Describe("replace", func() {
+		It("allows error description", func() {
+			opDefs := []OpDefinition{{Type: "replace", Path: &path, Value: &val, Error: &errorMsg}}
+
+			ops, err := NewOpsFromDefinitions(opDefs)
+			Expect(err).ToNot(HaveOccurred())
+
+			Expect(ops).To(Equal(Ops([]Op{
+				DescriptiveOp{
+					Op:       ReplaceOp{Path: MustNewPointerFromString("/abc"), Value: 123},
+					ErrorMsg: errorMsg,
+				},
+			})))
+		})
+
 		It("requires path", func() {
 			_, err := NewOpsFromDefinitions([]OpDefinition{{Type: "replace"}})
 			Expect(err).To(HaveOccurred())
@@ -89,6 +104,20 @@ var _ = Describe("NewOpsFromDefinitions", func() {
 	})
 
 	Describe("remove", func() {
+		It("allows error description", func() {
+			opDefs := []OpDefinition{{Type: "remove", Path: &path, Error: &errorMsg}}
+
+			ops, err := NewOpsFromDefinitions(opDefs)
+			Expect(err).ToNot(HaveOccurred())
+
+			Expect(ops).To(Equal(Ops([]Op{
+				DescriptiveOp{
+					Op:       RemoveOp{Path: MustNewPointerFromString("/abc")},
+					ErrorMsg: errorMsg,
+				},
+			})))
+		})
+
 		It("requires path", func() {
 			_, err := NewOpsFromDefinitions([]OpDefinition{{Type: "remove"}})
 			Expect(err).To(HaveOccurred())

patch/ops.go

@@ -11,6 +11,7 @@ var _ Op = Ops{}
 var _ Op = ReplaceOp{}
 var _ Op = RemoveOp{}
 var _ Op = FindOp{}
+var _ Op = DescriptiveOp{}
 var _ Op = ErrOp{}
 
 func (ops Ops) Apply(doc interface{}) (interface{}, error) {