config-entry: use custom MarshalJSON for mesh type

So that the Kind field is added to the JSON object.

agent/config_endpoint_test.go

@@ -7,10 +7,11 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	"github.com/hashicorp/consul/agent/structs"
-	"github.com/hashicorp/consul/testrpc"
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
+
+	"github.com/hashicorp/consul/agent/structs"
+	"github.com/hashicorp/consul/testrpc"
 )
 
 func TestConfig_Get(t *testing.T) {
@@ -48,6 +49,18 @@ func TestConfig_Get(t *testing.T) {
 				},
 			},
 		},
+		{
+			Datacenter: "dc1",
+			Entry: &structs.MeshConfigEntry{
+				TransparentProxy: structs.TransparentProxyMeshConfig{
+					CatalogDestinationsOnly: true,
+				},
+				Meta: map[string]string{
+					"key1": "value1",
+					"key2": "value2",
+				},
+			},
+		},
 	}
 	for _, req := range reqs {
 		out := false
@@ -95,6 +108,37 @@ func TestConfig_Get(t *testing.T) {
 		_, err := a.srv.Config(resp, req)
 		require.Error(t, errors.New("Must provide either a kind or both kind and name"), err)
 	})
+	t.Run("get the single mesh config", func(t *testing.T) {
+		req, _ := http.NewRequest("GET", "/v1/config/mesh/mesh", nil)
+		resp := httptest.NewRecorder()
+		obj, err := a.srv.Config(resp, req)
+		require.NoError(t, err)
+
+		ce, ok := obj.(*structs.MeshConfigEntry)
+		require.True(t, ok, "wrong type %T", obj)
+		// Set indexes to expected values for assertions
+		ce.CreateIndex = 12
+		ce.ModifyIndex = 13
+
+		out, err := a.srv.marshalJSON(req, obj)
+		require.NoError(t, err)
+
+		expected := `
+{
+	"Kind": "mesh",
+	"TransparentProxy": {
+		"CatalogDestinationsOnly": true
+	},
+	"Meta":{
+		"key1": "value1",
+		"key2": "value2"
+	},
+	"CreateIndex": 12,
+	"ModifyIndex": 13
+}
+`
+		require.JSONEq(t, expected, string(out))
+	})
 }
 
 func TestConfig_Delete(t *testing.T) {

agent/structs/config_entry_mesh.go

@@ -1,6 +1,7 @@
 package structs
 
 import (
+	"encoding/json"
 	"fmt"
 
 	"github.com/hashicorp/consul/acl"
@@ -88,3 +89,19 @@ func (e *MeshConfigEntry) GetEnterpriseMeta() *EnterpriseMeta {
 
 	return &e.EnterpriseMeta
 }
+
+// MarshalJSON adds the Kind field so that the JSON can be decoded back into the
+// correct type.
+// This method is implemented on the structs type (as apposed to the api type)
+// because that is what the API currently uses to return a response.
+func (e *MeshConfigEntry) MarshalJSON() ([]byte, error) {
+	type Alias MeshConfigEntry
+	source := &struct {
+		Kind string
+		*Alias
+	}{
+		Kind:  MeshConfig,
+		Alias: (*Alias)(e),
+	}
+	return json.Marshal(source)
+}

api/config_entry_cluster.go

@@ -1,7 +1,8 @@
 package api
 
+import "encoding/json"
+
 type MeshConfigEntry struct {
-	Name             string
 	Namespace        string                     `json:",omitempty"`
 	TransparentProxy TransparentProxyMeshConfig `alias:"transparent_proxy"`
 	Meta             map[string]string          `json:",omitempty"`
@@ -36,3 +37,17 @@ func (e *MeshConfigEntry) GetCreateIndex() uint64 {
 func (e *MeshConfigEntry) GetModifyIndex() uint64 {
 	return e.ModifyIndex
 }
+
+// MarshalJSON adds the Kind field so that the JSON can be decoded back into the
+// correct type.
+func (e *MeshConfigEntry) MarshalJSON() ([]byte, error) {
+	type Alias MeshConfigEntry
+	source := &struct {
+		Kind string
+		*Alias
+	}{
+		Kind:  MeshConfig,
+		Alias: (*Alias)(e),
+	}
+	return json.Marshal(source)
+}

command/config/write/config_write_test.go

@@ -1,6 +1,7 @@
 package write
 
 import (
+	"bytes"
 	"io"
 	"strings"
 	"testing"
@@ -113,6 +114,36 @@ func TestConfigWrite(t *testing.T) {
 		require.NotEqual(t, 0, code)
 		require.NotEmpty(t, ui.ErrorWriter.String())
 	})
+
+	t.Run("mesh config entry", func(t *testing.T) {
+		stdin := new(bytes.Buffer)
+		stdin.WriteString(`
+kind = "mesh"
+meta {
+	"foo" = "bar"
+	"gir" = "zim"
+}
+transparent_proxy {
+	catalog_destinations_only = true
+}
+`)
+
+		ui := cli.NewMockUi()
+		c := New(ui)
+		c.testStdin = stdin
+
+		code := c.Run([]string{"-http-addr=" + a.HTTPAddr(), "-"})
+		require.Empty(t, ui.ErrorWriter.String())
+		require.Contains(t, ui.OutputWriter.String(),
+			`Config entry written: mesh/mesh`)
+		require.Equal(t, 0, code)
+
+		entry, _, err := client.ConfigEntries().Get(api.MeshConfig, api.MeshConfigMesh, nil)
+		require.NoError(t, err)
+		proxy, ok := entry.(*api.MeshConfigEntry)
+		require.True(t, ok)
+		require.Equal(t, map[string]string{"foo": "bar", "gir": "zim"}, proxy.Meta)
+	})
 }
 
 // TestParseConfigEntry is the 'api' mirror image of