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rpc.go
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rpc.go
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package rpc // import "gopkg.in/src-d/proteus.v1/rpc"
import (
"fmt"
"go/ast"
"go/printer"
"go/token"
"os"
"path/filepath"
"strings"
"gopkg.in/src-d/proteus.v1/protobuf"
"gopkg.in/src-d/proteus.v1/report"
"gopkg.in/src-d/go-parse-utils.v1"
)
// Generator generates implementations of an RPC server for a package.
// It will declare a new type with the following name: {serviceName}Server
// with the first letter in lower case. In case the type already exists in the
// package, it will not be generated again. The purpose of that is that you can
// customize the type, even though the methods are automatically generated.
// Same happens with the constructor. If it does not exist, a function named
// new{ServiceName}Server with no parameters and a single result of the type
// {serviceName}Server will be generated. It can be defined, to avoid a default
// implementation, but the same signature is required, as it is used for
// registering the server implementation.
//
// So, if you have a service named FooService, you can implement
// `fooServiceServer` and `func newFooServiceServer() *fooServiceServer`.
//
// All generated methods will use as receiver a field in the server
// implementation with the same name as the type of the receiver.
// For example, the method generated for `func (*Foo) Bar()` will be require
// that our `fooServiceServer` had a field with that name.
//
// type fooServiceServer struct {
// Foo *Foo
// }
//
// For every method you want to generate an RPC method for, you have to
// implement its receiver by yourself in the server implementation type and the
// constructor.
//
// A single file per package will be generated containing all the RPC methods.
// The file will be written to the package path and it will be named
// "server.proteus.go"
type Generator struct {
importer *parseutil.Importer
}
// NewGenerator creates a new Generator.
func NewGenerator() *Generator {
return &Generator{parseutil.NewImporter()}
}
// Generate creates a new file in the package at the given path and implements
// the server according to the given proto package.
func (g *Generator) Generate(proto *protobuf.Package, path string) error {
if len(proto.RPCs) == 0 {
report.Warn("no RPCs in the given proto file, not generating anything")
return nil
}
pkg, err := g.importer.ImportWithFilters(
path,
parseutil.FileFilters{
func(pkg, file string, typ parseutil.FileType) bool {
return !strings.HasSuffix(file, ".pb.go")
},
func(pkg, file string, typ parseutil.FileType) bool {
return !strings.HasSuffix(file, ".proteus.go")
},
},
)
if err != nil {
return err
}
ctx := &context{
implName: serviceImplName(proto),
constructorName: constructorName(proto),
proto: proto,
pkg: pkg,
}
var decls []ast.Decl
if !ctx.isNameDefined(ctx.implName) {
decls = append(decls, g.declImplType(ctx.implName))
}
if !ctx.isNameDefined(ctx.constructorName) {
report.Warn("constructor %s for service %s is not implemented", ctx.implName, ctx.constructorName)
decls = append(decls, g.declConstructor(ctx.implName, ctx.constructorName))
}
for _, rpc := range proto.RPCs {
decls = append(decls, g.declMethod(ctx, rpc))
}
return g.writeFile(g.buildFile(ctx, decls), path)
}
func (g *Generator) declImplType(implName string) ast.Decl {
return &ast.GenDecl{
Tok: token.TYPE,
Specs: []ast.Spec{
&ast.TypeSpec{
Name: ast.NewIdent(implName),
Type: &ast.StructType{
Fields: fields(),
},
},
},
}
}
func (g *Generator) declConstructor(implName, constructorName string) ast.Decl {
return &ast.FuncDecl{
Name: ast.NewIdent(constructorName),
Type: &ast.FuncType{
Params: fields(),
Results: fields(&ast.Field{
Type: ptr(ast.NewIdent(implName)),
}),
},
Body: &ast.BlockStmt{
List: []ast.Stmt{
&ast.ReturnStmt{
Results: []ast.Expr{
&ast.UnaryExpr{
Op: token.AND,
X: &ast.CompositeLit{
Type: ast.NewIdent(implName),
},
},
},
},
},
},
}
}
func (g *Generator) genMethodType(ctx *context, rpc *protobuf.RPC) *ast.FuncType {
var in, out string
if isGenerated(rpc.Input) {
in = typeName(rpc.Input)
} else {
in = ctx.argumentType(rpc)
}
if isGenerated(rpc.Output) {
out = typeName(rpc.Output)
} else {
out = ctx.returnType(rpc)
}
return &ast.FuncType{
Params: fields(
field("ctx", ast.NewIdent("context.Context")),
field("in", ptr(ast.NewIdent(in))),
),
Results: fields(
field("result", ptr(ast.NewIdent(out))),
field("err", ast.NewIdent("error")),
),
}
}
func (g *Generator) genMethodCall(ctx *context, rpc *protobuf.RPC) ast.Expr {
call := &ast.CallExpr{Fun: ast.NewIdent(rpc.Method)}
if rpc.Recv != "" {
call.Fun = ast.NewIdent(fmt.Sprintf("s.%s.%s", rpc.Recv, rpc.Method))
}
if rpc.IsVariadic {
call.Ellipsis = token.Pos(1)
}
if !isGenerated(rpc.Input) {
call.Args = append(call.Args, ast.NewIdent("in"))
} else {
msg := ctx.findMessage(typeName(rpc.Input))
for i := range msg.Fields {
call.Args = append(call.Args, ast.NewIdent(fmt.Sprintf(
"in.Arg%d", i+1,
)))
}
}
return call
}
func (g *Generator) genBaseMethodBody(methodType *ast.FuncType) *ast.BlockStmt {
return &ast.BlockStmt{
List: []ast.Stmt{
&ast.AssignStmt{
Tok: token.ASSIGN,
Lhs: []ast.Expr{ast.NewIdent("result")},
Rhs: []ast.Expr{
&ast.CallExpr{
Fun: ast.NewIdent("new"),
Args: []ast.Expr{
methodType.Results.List[0].Type.(*ast.StarExpr).X,
},
},
},
},
},
}
}
func (g *Generator) genMethodBody(ctx *context, rpc *protobuf.RPC, typ *ast.FuncType) *ast.BlockStmt {
if !isGenerated(rpc.Output) {
return g.genMethodBodyForNotGeneratedOutput(ctx, rpc, typ)
} else {
return g.genMethodBodyForGeneratedOutput(ctx, rpc, typ)
}
}
func (g *Generator) genMethodBodyAssignmentsForGeneratedOutput(ctx *context, rpc *protobuf.RPC, msg *protobuf.Message) (lhs []ast.Expr) {
for i, f := range msg.Fields {
if f == nil {
lhs = append(lhs, ast.NewIdent("_"))
} else {
lhs = append(lhs, ast.NewIdent(fmt.Sprintf(
"result.Result%d", i+1,
)))
}
}
return
}
func emptyBodyForMethodCall(body *ast.BlockStmt, methodCall ast.Expr) *ast.BlockStmt {
body.List = []ast.Stmt{
&ast.ExprStmt{
X: methodCall,
},
new(ast.ReturnStmt),
}
return body
}
func (g *Generator) genMethodBodyForGeneratedOutput(ctx *context, rpc *protobuf.RPC, typ *ast.FuncType) *ast.BlockStmt {
body := g.genBaseMethodBody(typ)
methodCall := g.genMethodCall(ctx, rpc)
call := &ast.AssignStmt{
Tok: token.ASSIGN,
Rhs: []ast.Expr{methodCall},
}
msg := ctx.findMessage(typeName(rpc.Output))
if len(msg.Fields) == 0 && !rpc.HasError {
return emptyBodyForMethodCall(body, methodCall)
} else if len(msg.Fields) == 0 {
body.List = nil
}
body.List = append(body.List, call)
lhs := g.genMethodBodyAssignmentsForGeneratedOutput(ctx, rpc, msg)
call.Lhs = append(call.Lhs, lhs...)
if rpc.HasError {
call.Lhs = append(call.Lhs, ast.NewIdent("err"))
}
body.List = append(body.List, new(ast.ReturnStmt))
return body
}
func (g *Generator) genMethodBodyForNotGeneratedOutput(ctx *context, rpc *protobuf.RPC, typ *ast.FuncType) *ast.BlockStmt {
body := g.genBaseMethodBody(typ)
methodCall := g.genMethodCall(ctx, rpc)
call := &ast.AssignStmt{Tok: token.ASSIGN}
needToAddressOutput := !isGenerated(rpc.Output) && !rpc.Output.IsNullable()
// Specific code
if needToAddressOutput {
call.Lhs = append(call.Lhs, ast.NewIdent("aux"))
call.Tok = token.DEFINE
} else {
call.Lhs = append(call.Lhs, ast.NewIdent("result"))
}
if rpc.HasError {
call.Lhs = append(call.Lhs, ast.NewIdent("err"))
}
call.Rhs = append(call.Rhs, methodCall)
body.List = append(body.List, call)
if needToAddressOutput {
body.List = append(body.List, &ast.AssignStmt{
Tok: token.ASSIGN,
Lhs: []ast.Expr{ast.NewIdent("result")},
Rhs: []ast.Expr{
&ast.UnaryExpr{
Op: token.AND,
X: ast.NewIdent("aux"),
},
},
})
}
body.List = append(body.List, new(ast.ReturnStmt))
return body
}
func (g *Generator) declMethod(ctx *context, rpc *protobuf.RPC) ast.Decl {
typ := g.genMethodType(ctx, rpc)
return &ast.FuncDecl{
Recv: fields(field("s", ptr(ast.NewIdent(ctx.implName)))),
Name: ast.NewIdent(rpc.Name),
Type: typ,
Body: g.genMethodBody(ctx, rpc, typ),
}
}
func (g *Generator) buildFile(ctx *context, decls []ast.Decl) *ast.File {
f := &ast.File{
Name: ast.NewIdent(ctx.pkg.Name()),
}
var specs = []ast.Spec{newImport("golang.org/x/net/context")}
for _, i := range ctx.imports {
specs = append(specs, newImport(i))
}
f.Decls = append(f.Decls, &ast.GenDecl{
Tok: token.IMPORT,
Lparen: token.Pos(1),
Specs: specs,
})
f.Decls = append(f.Decls, decls...)
return f
}
func (g *Generator) writeFile(file *ast.File, path string) error {
fileName := filepath.Join(goSrc, path, "server.proteus.go")
f, err := os.Create(fileName)
if err != nil {
return err
}
defer f.Close()
return printer.Fprint(f, token.NewFileSet(), file)
}
func typeName(t protobuf.Type) string {
if typ, ok := t.(*protobuf.Named); ok {
return typ.Name
}
return ""
}
func isGenerated(t protobuf.Type) bool {
if typ, ok := t.(*protobuf.Named); ok {
return typ.Generated
}
return false
}
// shorthands for some AST structures
func newImport(path string) *ast.ImportSpec {
return &ast.ImportSpec{
Path: &ast.BasicLit{
Kind: token.STRING,
Value: fmt.Sprintf(`"%s"`, removeGoPath(path)),
},
}
}
func field(name string, typ ast.Expr) *ast.Field {
return &ast.Field{
Names: []*ast.Ident{ast.NewIdent(name)},
Type: typ,
}
}
func fields(fields ...*ast.Field) *ast.FieldList {
return &ast.FieldList{List: fields}
}
func ptr(expr ast.Expr) ast.Expr {
return &ast.StarExpr{X: expr}
}
var goSrc = filepath.Join(os.Getenv("GOPATH"), "src")
func removeGoPath(path string) string {
return strings.TrimLeft(strings.Replace(path, goSrc, "", -1), "/")
}