Most basic marshal

.gitignore

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+.idea
+vendor
+go.sum

README.md

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+# JSONry
+
+A Go module for converting between a Go `struct` and JSON.
+
+JSONry is being extracted from the [Cloud Foundry CLI](https://github.com/cloudfoundry/cli) project. It exists to make it easier
+to define the translation between complex JSON data and Go structures.

go.mod

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+module code.cloudfoundry.org/jsonry
+
+go 1.13
+
+require (
+	github.com/onsi/ginkgo v1.12.0
+	github.com/onsi/gomega v1.9.0
+)

jsonry_suite_test.go

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+package jsonry_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+func TestJSONry(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "JSONry Suite")
+}

marshal.go

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+package jsonry
+
+import (
+	"encoding/json"
+	"errors"
+	"reflect"
+)
+
+func Marshal(input interface{}) ([]byte, error) {
+	i := reflect.ValueOf(input)
+
+	if i.Kind()==reflect.Ptr {
+		i = i.Elem()
+	}
+
+	if i.Kind() != reflect.Struct {
+		return nil, errors.New("the input must be a struct")
+	}
+
+	m, err := marshal(i)
+	if err != nil {
+		return nil, err
+	}
+
+	return json.Marshal(m)
+}
+
+func marshal(in reflect.Value) (map[string]interface{}, error) {
+	out := make(map[string]interface{})
+
+	t := in.Type()
+	for i := 0; i<t.NumField(); i++ {
+		f := t.Field(i)
+		out[f.Name] = in.Field(i).Interface()
+	}
+
+	return out, nil
+}

marshal_test.go

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+package jsonry_test
+
+import (
+	"code.cloudfoundry.org/jsonry"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Marshal", func() {
+	Describe("basic types", func() {
+		It("basic", func() {
+			type t struct{A string}
+			out, err := jsonry.Marshal(t{A:"hello"})
+			Expect(err).NotTo(HaveOccurred())
+			Expect(out).To(MatchJSON(`{"A":"hello"}`))
+		})
+	})
+
+	Describe("inputs", func() {
+		It("accept a struct", func() {
+			var s struct{}
+			_, err := jsonry.Marshal(s)
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		It("accept a struct pointer", func() {
+			var s struct{}
+			_, err := jsonry.Marshal(&s)
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		It("rejects a non-struct value", func() {
+			_, err := jsonry.Marshal(42)
+			Expect(err).To(MatchError("the input must be a struct"))
+		})
+
+		It("rejects a nil pointer", func() {
+			type s struct{}
+			var sp *s
+			_, err := jsonry.Marshal(sp)
+			Expect(err).To(MatchError("the input must be a struct"))
+		})
+	})
+})