Generate Mojom Types in Go

mojo/public/go/application/connection.go

Index: mojo/public/go/application/connection.go
diff --git a/mojo/public/go/application/connection.go b/mojo/public/go/application/connection.go
index f3be55c9a691443630e02d33e3d7bbfe3ffe38db..b226cf133c5bf722c34c3da90e1c23b7110ac815 100644
--- a/mojo/public/go/application/connection.go
+++ b/mojo/public/go/application/connection.go
@@ -11,6 +11,7 @@ import (
 	"mojo/public/go/system"
 
 	sp "mojo/public/interfaces/application/service_provider"
+	"mojo/public/interfaces/bindings/service_describer"
 )
 
 type connectionInfo struct {
@@ -34,6 +35,10 @@ type ServiceRequest interface {
 	// Name returns the name of requested mojo service.
 	Name() string
 
+	// ServiceDescription returns a service description, which can be queried to
+	// examine the type information of the requested mojo service.
+	ServiceDescription() service_describer.ServiceDescription
+
 	// PassMessagePipe passes ownership of the underlying message pipe
 	// handle to the newly created handle object, invalidating the
 	// underlying handle object in the process.
@@ -45,6 +50,10 @@ type ServiceFactory interface {
 	// Name returns the name of provided mojo service.
 	Name() string
 
+	// ServiceDescription returns a service description, which can be queried to
+	// examine the type information of the provided mojo service.

[rudominer, 2015/10/20 21:14:06]

s/the provided mojo service/the mojo service/.

The problem with "the provided mojo services" is that it sounds like the caller
of ServiceDescription() is providing it.

[alexfandrianto, 2015/10/20 23:08:03]

Done. My original reason for having it was to echo the comment for Name(), which
also says 'provided mojo service'.

+	ServiceDescription() service_describer.ServiceDescription
+
 	// Create binds an implementation of mojo service to the provided
 	// message pipe and runs it.
 	Create(pipe system.MessagePipeHandle)
@@ -62,6 +71,7 @@ type Connection struct {
 	localServices      *bindings.Stub
 	outgoingConnection *OutgoingConnection
 	isClosed           bool
+	describer          *ServiceDescriberFactory
 }
 
 func newConnection(requestorURL string, services *sp.ServiceProvider_Request, exposedServices *sp.ServiceProvider_Pointer, resolvedURL string) *Connection {
@@ -122,6 +132,22 @@ func (c *Connection) ProvideServices(services ...ServiceFactory) *OutgoingConnec
 	return c.outgoingConnection
 }
 
+// ProvideServicesWithDescriber calls ProvideServices with a ServiceDescriber.
+// The ServiceDescriber will have knowledge of all of the services passed in.

[rudominer, 2015/10/20 21:14:06]

This method is part of the API consumed by an application developer and so this
comment should be written in a way that will help that person. I think this
comment should say something like the following:

ProvideServicesWithDescriber is an alternative to ProvideServices that, in
addition to providing the given services, also provides type descriptions of the
given services. See ProvideServices for a description of what it does. This
method will invoke ProvideServices after appending one additional service to
|services| namely the ServiceDescriber service. Client Mojo applications may
request the ServiceDescriber service using the name "_ServiceDescriber". See
service_describer.mojom for a description of the ServiceDescriber interface. The
implementation of ServiceDescriber given will be able to describe the services
listed in |services|.
Note that the implementation of ServiceDescriber will make the optional
DeclarationData available on all types and in particular names used in .mojom
files will be exposed to client applications.

[alexfandrianto, 2015/10/20 23:08:03]

I improved the comment with most of your suggestions.

One thing that stuck out to me is the interface name. When I was implementing my
proxy, I was able to connect normally without explicitly mentioning the name:

r, p := service_describer.CreateMessagePipeForServiceDescriber()
fs.appctx.ConnectToApplication(mojourl).ConnectToService(&r)
sDescriber := service_describer.NewServiceDescriberProxy(p,
bindings.GetAsyncWaiter())
defer sDescriber.Close_Proxy()

+func (c *Connection) ProvideServicesWithDescriber(services ...ServiceFactory) *OutgoingConnection {
+	if c.servicesProvided {
+		panic("ProvideServices can be called only once")

[rudominer, 2015/10/20 21:14:06]

"ProvideServices or ProvideServicesWithDescriber can be called only once"

[alexfandrianto, 2015/10/20 23:08:03]

That's true. Done.

+	}
+	mapping := make(map[string]service_describer.ServiceDescription)
+	for _, service := range services {
+		mapping[service.Name()] = service.ServiceDescription()
+	}
+	c.describer = newServiceDescriberFactory(mapping)
+	servicesWithDescriber := append(services, &service_describer.ServiceDescriber_ServiceFactory{c.describer})
+
+	return c.ProvideServices(servicesWithDescriber...)
+}
+
 // Close closes both incoming and outgoing parts of the connection.
 func (c *Connection) Close() {
 	if c.servicesRequest != nil {
@@ -130,6 +156,9 @@ func (c *Connection) Close() {
 	if c.localServices != nil {
 		c.localServices.Close()
 	}
+	if c.describer != nil {
+		c.describer.Close()
+	}
 	if c.outgoingConnection.remoteServices != nil {
 		c.outgoingConnection.remoteServices.Close_Proxy()
 	}