pkg/plugins/pluginrpc-gen/parser.go

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package main
import (
"errors"
"fmt"
"go/ast"
"go/parser"
"go/token"
"reflect"
"strings"
)
var ErrBadReturn = errors.New("found return arg with no name: all args must be named")
type ErrUnexpectedType struct {
expected string
actual interface{}
}
func (e ErrUnexpectedType) Error() string {
return fmt.Sprintf("got wrong type expecting %s, got: %v", e.expected, reflect.TypeOf(e.actual))
}
type parsedPkg struct {
Name string
Functions []function
}
type function struct {
Name string
Args []arg
Returns []arg
Doc string
}
type arg struct {
Name string
ArgType string
}
func (a *arg) String() string {
return strings.ToLower(a.Name) + " " + strings.ToLower(a.ArgType)
}
// Parses the given file for an interface definition with the given name
func Parse(filePath string, objName string) (*parsedPkg, error) {
fs := token.NewFileSet()
pkg, err := parser.ParseFile(fs, filePath, nil, parser.AllErrors)
if err != nil {
return nil, err
}
p := &parsedPkg{}
p.Name = pkg.Name.Name
obj, exists := pkg.Scope.Objects[objName]
if !exists {
return nil, fmt.Errorf("could not find object %s in %s", objName, filePath)
}
if obj.Kind != ast.Typ {
return nil, fmt.Errorf("exected type, got %s", obj.Kind)
}
spec, ok := obj.Decl.(*ast.TypeSpec)
if !ok {
return nil, ErrUnexpectedType{"*ast.TypeSpec", obj.Decl}
}
iface, ok := spec.Type.(*ast.InterfaceType)
if !ok {
return nil, ErrUnexpectedType{"*ast.InterfaceType", spec.Type}
}
p.Functions, err = parseInterface(iface)
if err != nil {
return nil, err
}
return p, nil
}
func parseInterface(iface *ast.InterfaceType) ([]function, error) {
var functions []function
for _, field := range iface.Methods.List {
switch f := field.Type.(type) {
case *ast.FuncType:
method, err := parseFunc(field)
if err != nil {
return nil, err
}
if method == nil {
continue
}
functions = append(functions, *method)
case *ast.Ident:
spec, ok := f.Obj.Decl.(*ast.TypeSpec)
if !ok {
return nil, ErrUnexpectedType{"*ast.TypeSpec", f.Obj.Decl}
}
iface, ok := spec.Type.(*ast.InterfaceType)
if !ok {
return nil, ErrUnexpectedType{"*ast.TypeSpec", spec.Type}
}
funcs, err := parseInterface(iface)
if err != nil {
fmt.Println(err)
continue
}
functions = append(functions, funcs...)
default:
return nil, ErrUnexpectedType{"*astFuncType or *ast.Ident", f}
}
}
return functions, nil
}
func parseFunc(field *ast.Field) (*function, error) {
f := field.Type.(*ast.FuncType)
method := &function{Name: field.Names[0].Name}
if _, exists := skipFuncs[method.Name]; exists {
fmt.Println("skipping:", method.Name)
return nil, nil
}
if f.Params != nil {
args, err := parseArgs(f.Params.List)
if err != nil {
return nil, err
}
method.Args = args
}
if f.Results != nil {
returns, err := parseArgs(f.Results.List)
if err != nil {
return nil, fmt.Errorf("error parsing function returns for %q: %v", method.Name, err)
}
method.Returns = returns
}
return method, nil
}
func parseArgs(fields []*ast.Field) ([]arg, error) {
var args []arg
for _, f := range fields {
if len(f.Names) == 0 {
return nil, ErrBadReturn
}
for _, name := range f.Names {
var typeName string
switch argType := f.Type.(type) {
case *ast.Ident:
typeName = argType.Name
case *ast.StarExpr:
i, ok := argType.X.(*ast.Ident)
if !ok {
return nil, ErrUnexpectedType{"*ast.Ident", f.Type}
}
typeName = "*" + i.Name
default:
return nil, ErrUnexpectedType{"*ast.Ident or *ast.StarExpr", f.Type}
}
args = append(args, arg{name.Name, typeName})
}
}
return args, nil
}