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// Copyright 2019 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package gocode
import (
"bytes"
"fmt"
"go/ast"
"go/format"
"go/types"
"text/template"
"golang.org/x/tools/go/packages"
"cuelang.org/go/cue"
"cuelang.org/go/cue/errors"
"cuelang.org/go/internal/value"
)
// Config defines options for generation Go code.
type Config struct {
// Prefix is used as a prefix to all generated variables. It defaults to
// cuegen.
Prefix string
// ValidateName defines the default name for validation methods or prefix
// for validation functions. The default is "Validate". Set to "-" to
// disable generating validators.
ValidateName string
// CompleteName defines the default name for complete methods or prefix
// for complete functions. The default is "-" (disabled).
CompleteName string
// The cue.Runtime variable name to use for initializing Codecs.
// A new Runtime is created by default.
RuntimeVar string
}
const defaultPrefix = "cuegen"
// Generate generates Go code for the given instance in the directory of the
// given package.
//
// Generate converts top-level declarations to corresponding Go code. By default,
// it will only generate validation functions of methods for exported top-level
// declarations. The behavior can be altered with the @go attribute.
//
// The go attribute has the following form @go(<name>{,<option>}), where option
// is either a key-value pair or a flag. The name maps the CUE name to an
// alternative Go name. The special value '-' is used to indicate the field
// should be ignored for any Go generation.
//
// The following options are supported:
//
// type=<gotype> The Go type as which this value should be interpreted.
// This defaults to the type with the (possibly overridden)
// name of the field.
// validate=<name> Alternative name for the validation function or method
// Setting this to the empty string disables generation.
// complete=<name> Alternative name for the validation function or method.
// Setting this to the empty string disables generation.
// func Generate as a function instead of a method.
//
//
// Selection and Naming
//
// Generate will not generate any code for fields that have no go attribute
// and that are not exported or for which there is no namesake Go type.
// If the go attribute has the special value '-' as its name it wil be dropped
// as well. In all other cases Generate will generate Go code, even if the
// resulting code will not compile. For instance, Generate will generate Go
// code even if the user defines a Go type in the attribute that does not
// exist.
//
// If a field selected for generation and the go name matches that the name of
// the Go type, the corresponding validate and complete code are generated as
// methods by default. If not, it will be generated as a function. The default
// function name is the default operation name with the Go name as a suffix.
//
//
// Caveats
// Currently not supported:
// - option to generate Go structs (or automatically generate if undefined)
// - for type option to refer to types outside the package.
//
func Generate(pkgPath string, inst *cue.Instance, c *Config) (b []byte, err error) {
// TODO: if inst is nil, the instance is loaded from CUE files in the same
// package directory with the same package name.
if err = inst.Value().Validate(); err != nil {
return nil, err
}
if c == nil {
c = &Config{}
}
g := &generator{
Config: *c,
typeMap: map[string]types.Type{},
}
pkgName := inst.PkgName
if pkgPath != "" {
loadCfg := &packages.Config{
Mode: packages.NeedName | packages.NeedFiles | packages.NeedCompiledGoFiles | packages.NeedImports | packages.NeedTypes | packages.NeedTypesSizes | packages.NeedSyntax | packages.NeedTypesInfo | packages.NeedDeps,
}
pkgs, err := packages.Load(loadCfg, pkgPath)
if err != nil {
return nil, fmt.Errorf("generating failed: %v", err)
}
if len(pkgs) != 1 {
return nil, fmt.Errorf(
"generate only allowed for one package at a time, found %d",
len(pkgs))
}
g.pkg = pkgs[0]
if len(g.pkg.Errors) > 0 {
for _, err := range g.pkg.Errors {
g.addErr(err)
}
return nil, g.err
}
pkgName = g.pkg.Name
for _, obj := range g.pkg.TypesInfo.Defs {
if obj == nil || obj.Pkg() != g.pkg.Types || obj.Parent() == nil {
continue
}
g.typeMap[obj.Name()] = obj.Type()
}
}
// TODO: add package doc if there is no existing Go package or if it doesn't
// have package documentation already.
g.exec(headerCode, map[string]string{
"pkgName": pkgName,
})
iter, err := inst.Value().Fields(cue.Definitions(true))
g.addErr(err)
for iter.Next() {
g.decl(iter.Label(), iter.Value())
}
r := value.ConvertToRuntime(inst.Value().Context())
b, err = r.Marshal(inst)
g.addErr(err)
g.exec(loadCode, map[string]string{
"runtime": g.RuntimeVar,
"prefix": strValue(g.Prefix, defaultPrefix),
"data": string(b),
})
if g.err != nil {
return nil, g.err
}
b, err = format.Source(g.w.Bytes())
if err != nil {
// Return bytes as well to allow analysis of the failed Go code.
return g.w.Bytes(), err
}
return b, err
}
type generator struct {
Config
pkg *packages.Package
typeMap map[string]types.Type
w bytes.Buffer
err errors.Error
}
func (g *generator) addErr(err error) {
if err != nil {
g.err = errors.Append(g.err, errors.Promote(err, "generate failed"))
}
}
func (g *generator) exec(t *template.Template, data interface{}) {
g.addErr(t.Execute(&g.w, data))
}
func (g *generator) decl(name string, v cue.Value) {
attr := v.Attribute("go")
if !ast.IsExported(name) && attr.Err() != nil {
return
}
goName := name
switch s, _ := attr.String(0); s {
case "":
case "-":
return
default:
goName = s
}
goTypeName := goName
goType := ""
if str, ok, _ := attr.Lookup(1, "type"); ok {
goType = str
goTypeName = str
}
isFunc, _ := attr.Flag(1, "func")
if goTypeName != goName {
isFunc = true
}
zero := "nil"
typ, ok := g.typeMap[goTypeName]
if !ok && !mappedGoTypes(goTypeName) {
return
}
if goType == "" {
goType = goTypeName
if typ != nil {
switch typ.Underlying().(type) {
case *types.Struct, *types.Array:
goType = "*" + goTypeName
zero = fmt.Sprintf("&%s{}", goTypeName)
case *types.Pointer:
zero = fmt.Sprintf("%s(nil)", goTypeName)
isFunc = true
}
}
}
g.exec(stubCode, map[string]interface{}{
"prefix": strValue(g.Prefix, defaultPrefix),
"cueName": name, // the field name of the CUE type
"goType": goType, // the receiver or argument type
"zero": zero, // the zero value of the underlying type
// @go attribute options
"func": isFunc,
"validate": lookupName(attr, "validate", strValue(g.ValidateName, "Validate")),
"complete": lookupName(attr, "complete", g.CompleteName),
})
}
func lookupName(attr cue.Attribute, option, config string) string {
name, ok, _ := attr.Lookup(1, option)
if !ok {
name = config
}
if name == "-" {
return ""
}
return name
}
func strValue(have, fallback string) string {
if have == "" {
return fallback
}
return have
}
func mappedGoTypes(s string) bool {
switch s {
case "bool", "float32", "float64",
"int", "int8", "int16", "int32", "int64", "string",
"uint", "uint8", "uint16", "uint32", "uint64":
return true
}
return false
}