yaml gotchas

Author: cppforlife

README.md

@@ -2,4 +2,5 @@
 
 Roughly based on JSON patch: https://tools.ietf.org/html/rfc6902.
 
-[Usage examples](docs/examples.md)
+- [Usage examples](docs/examples.md)
+- [Go YAML gotchas](docs/go-yaml.md)

docs/go-yaml.md

@@ -0,0 +1,5 @@
+## Go YAML
+
+Tests: [patch/yaml_compat_test.go](patch/yaml_compat_test.go)
+
+- Use `!!str ""` instead of `""`

patch/yaml_compat_test.go

@@ -0,0 +1,43 @@
+package patch_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"gopkg.in/yaml.v2"
+
+	. "github.com/cppforlife/go-patch/patch"
+)
+
+var _ = Describe("YAML compatibility", func() {
+	Describe("empty string", func() {
+		It("[WORKAROUND] works serializing empty strings", func() {
+			str := `
+- type: replace
+  path: /instance_groups/name=cloud_controller/instances
+  value: !!str ""
+`
+
+			var opDefs []OpDefinition
+
+			err := yaml.Unmarshal([]byte(str), &opDefs)
+			Expect(err).ToNot(HaveOccurred())
+
+			val := opDefs[0].Value
+			Expect((*val).(string)).To(Equal(""))
+		})
+
+		It("[PORBLEM] does not works serializing empty strings", func() {
+			str := `
+- type: replace
+  path: /instance_groups/name=cloud_controller/instances
+  value: ""
+`
+
+			var opDefs []OpDefinition
+
+			err := yaml.Unmarshal([]byte(str), &opDefs)
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("cannot unmarshal !!str"))
+		})
+	})
+})