entc/gen: add support for adding client fields using template

Summary: Pull Request resolved: https://github.com/facebookincubator/ent/pull/155

Reviewed By: alexsn

Differential Revision: D18421223

fbshipit-source-id: 112d4d26d53a64e2c78640c6d508ba2d1d3a7791

entc/gen/template/client.tmpl

@@ -34,6 +34,7 @@ type Client struct {
 		// {{ $n.Name }} is the client for interacting with the {{ $n.Name }} builders.
 		{{ $n.Name }} *{{ $n.Name }}Client
 	{{ end }}
+	{{ template "client/fields/additional" $ }}
 }
 
 // NewClient creates a new client configured with the given options.
@@ -204,3 +205,6 @@ func (c *{{ $client }}) Query{{ pascal $e.Name }}({{ $rec }} *{{ $n.Name }}) *{{
 {{ end }}
 {{ end }}
 
+{{/* A template that can be overrided in order to add additional fields to the client.*/}}
+{{ define "client/fields/additional" }}{{end}}
+

entc/integration/template/ent/client.go

@@ -10,6 +10,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"sync"
 
 	"github.com/facebookincubator/ent/entc/integration/template/ent/migrate"
 
@@ -32,6 +33,10 @@ type Client struct {
 	Pet *PetClient
 	// User is the client for interacting with the User builders.
 	User *UserClient
+
+	// additional fields.
+	sync.Mutex
+	tables []string
 }
 
 // NewClient creates a new client configured with the given options.

entc/integration/template/ent/template/client.tmpl

@@ -0,0 +1,11 @@
+{{/*
+Copyright 2019-present Facebook Inc. All rights reserved.
+This source code is licensed under the Apache 2.0 license found
+in the LICENSE file in the root directory of this source tree.
+*/}}
+
+{{ define "client/fields/additional" }}
+	// additional fields.
+	sync.Mutex
+	tables []string
+{{ end }}

entc/integration/template/template_test.go

@@ -42,4 +42,7 @@ func TestCustomTemplate(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, g.ID, node.ID)
 	require.Equal(t, &ent.Field{Type: "int", Name: "MaxUsers", Value: "10"}, node.Fields[0])
+
+	// compile time check for client fields.
+	_ = &client.Mutex
 }