internal/encoding/json/encode.go - cue - Git at Google

 // Copyright 2020 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 json

 import (
 	"bytes"
 	"encoding/json"
 	"math/big"
 	"strings"

 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/literal"
 	"cuelang.org/go/cue/token"
 	"cuelang.org/go/internal/astinternal"
 )

 // Encode converts a CUE AST to JSON.
 //
 // The given file must only contain values that can be directly supported by
 // JSON:
 //    Type          Restrictions
 //    BasicLit
 //    File          no imports, aliases, or definitions
 //    StructLit     no embeddings, aliases, or definitions
 //    List
 //    Field         must be regular; label must be a BasicLit or Ident
 //
 // Comments and attributes are ignored.
 func Encode(n ast.Node) (b []byte, err error) {
 	e := encoder{}
 	err = e.encode(n)
 	if err != nil {
 		return nil, err
 	}
 	return e.w.Bytes(), nil
 }

 type encoder struct {
 	w              bytes.Buffer
 	tab            []byte
 	indentsAtLevel []int
 	indenting      bool
 	unIndenting    int
 }

 func (e *encoder) writeIndent(b byte) {
 	if e.indenting {
 		e.indentsAtLevel[len(e.indentsAtLevel)-1]++
 	} else {
 		e.indentsAtLevel = append(e.indentsAtLevel, 0)
 	}
 	e.indenting = true
 	_ = e.w.WriteByte(b)
 }

 func (e *encoder) writeUnindent(b byte, pos, def token.Pos) {
 	if e.unIndenting > 0 {
 		e.unIndenting--
 	} else {
 		e.unIndenting = e.indentsAtLevel[len(e.indentsAtLevel)-1]
 		e.indentsAtLevel = e.indentsAtLevel[:len(e.indentsAtLevel)-1]
 	}
 	e.indenting = false
 	e.ws(pos, def.RelPos())
 	_ = e.w.WriteByte(b)
 }

 func (e *encoder) writeString(s string) {
 	_, _ = e.w.WriteString(s)
 	e.indenting = false
 }

 func (e *encoder) writeByte(b byte) {
 	_ = e.w.WriteByte(b)
 }

 func (e *encoder) write(b []byte) {
 	_, _ = e.w.Write(b)
 	e.indenting = false
 }

 func (e *encoder) indent() {
 	for range e.indentsAtLevel {
 		e.write(e.tab)
 	}
 }

 func (e *encoder) ws(pos token.Pos, default_ token.RelPos) {
 	rel := pos.RelPos()
 	if pos == token.NoPos {
 		rel = default_
 	}
 	switch rel {
 	case token.NoSpace:
 	case token.Blank:
 		e.writeByte(' ')
 	case token.Newline:
 		e.writeByte('\n')
 		e.indent()
 	case token.NewSection:
 		e.writeString("\n\n")
 		e.indent()
 	}
 }
 func (e *encoder) encode(n ast.Node) error {
 	if e.tab == nil {
 		e.tab = []byte("    ")
 	}
 	const defPos = token.NoSpace
 	switch x := n.(type) {
 	case *ast.BasicLit:
 		e.ws(x.Pos(), defPos)
 		return e.encodeScalar(x, true)

 	case *ast.ListLit:
 		e.ws(foldNewline(x.Pos()), token.NoRelPos)
 		if len(x.Elts) == 0 {
 			e.writeString("[]")
 			return nil
 		}
 		e.writeIndent('[')
 		for i, x := range x.Elts {
 			if i > 0 {
 				e.writeString(",")
 			}
 			if err := e.encode(x); err != nil {
 				return err
 			}
 		}
 		e.writeUnindent(']', x.Rbrack, compactNewline(x.Elts[0].Pos()))
 		return nil

 	case *ast.StructLit:
 		e.ws(foldNewline(n.Pos()), token.NoRelPos)
 		return e.encodeDecls(x.Elts, x.Rbrace)

 	case *ast.File:
 		return e.encodeDecls(x.Decls, token.NoPos)

 	case *ast.UnaryExpr:
 		e.ws(foldNewline(x.Pos()), defPos)
 		l, ok := x.X.(*ast.BasicLit)
 		if ok && x.Op == token.SUB && (l.Kind == token.INT || l.Kind == token.FLOAT) {
 			e.writeByte('-')
 			return e.encodeScalar(l, false)
 		}
 	}
 	return errors.Newf(n.Pos(), "json: unsupported node %s (%T)", astinternal.DebugStr(n), n)
 }

 func (e *encoder) encodeScalar(l *ast.BasicLit, allowMinus bool) error {
 	switch l.Kind {
 	case token.INT:
 		var x big.Int
 		return e.setNum(l, allowMinus, &x)

 	case token.FLOAT:
 		var x big.Float
 		return e.setNum(l, allowMinus, &x)

 	case token.TRUE:
 		e.writeString("true")

 	case token.FALSE:
 		e.writeString("false")

 	case token.NULL:
 		e.writeString("null")

 	case token.STRING:
 		str, err := literal.Unquote(l.Value)
 		if err != nil {
 			return err
 		}
 		b, err := json.Marshal(str)
 		if err != nil {
 			return err
 		}
 		e.write(b)

 	default:
 		return errors.Newf(l.Pos(), "unknown literal type %v", l.Kind)
 	}
 	return nil
 }

 func (e *encoder) setNum(l *ast.BasicLit, allowMinus bool, x interface{}) error {
 	if !allowMinus && strings.HasPrefix(l.Value, "-") {
 		return errors.Newf(l.Pos(), "double minus not allowed")
 	}
 	var ni literal.NumInfo
 	if err := literal.ParseNum(l.Value, &ni); err != nil {
 		return err
 	}
 	e.writeString(ni.String())
 	return nil
 }

 // encodeDecls converts a sequence of declarations to a value. If it encounters
 // an embedded value, it will return this expression. This is more relaxed for
 // structs than is currently allowed for CUE, but the expectation is that this
 // will be allowed at some point. The input would still be illegal CUE.
 func (e *encoder) encodeDecls(decls []ast.Decl, endPos token.Pos) error {
 	var embed ast.Expr
 	var fields []*ast.Field

 	for _, d := range decls {
 		switch x := d.(type) {
 		default:
 			return errors.Newf(x.Pos(), "json: unsupported node %s (%T)", astinternal.DebugStr(x), x)

 		case *ast.Package:
 			if embed != nil || fields != nil {
 				return errors.Newf(x.Pos(), "invalid package clause")
 			}
 			continue

 		case *ast.Field:
 			if x.Token == token.ISA {
 				return errors.Newf(x.TokenPos, "json: definition not allowed")
 			}
 			if x.Optional != token.NoPos {
 				return errors.Newf(x.Optional, "json: optional fields not allowed")
 			}
 			fields = append(fields, x)

 		case *ast.EmbedDecl:
 			if embed != nil {
 				return errors.Newf(x.Pos(), "json: multiple embedded values")
 			}
 			embed = x.Expr

 		case *ast.CommentGroup:
 		}
 	}

 	if embed != nil {
 		if fields != nil {
 			return errors.Newf(embed.Pos(), "json: embedding mixed with fields")
 		}
 		return e.encode(embed)
 	}

 	if len(fields) == 0 {
 		e.writeString("{}")
 		return nil
 	}

 	e.writeIndent('{')
 	pos := compactNewline(fields[0].Pos())
 	if endPos == token.NoPos && pos.RelPos() == token.Blank {
 		pos = token.NoPos
 	}
 	firstPos := pos
 	const defPos = token.NoRelPos
 	for i, x := range fields {
 		if i > 0 {
 			e.writeByte(',')
 			pos = x.Pos()
 		}
 		name, _, err := ast.LabelName(x.Label)
 		if err != nil {
 			return errors.Newf(x.Label.Pos(), "json: only literal labels allowed")
 		}
 		b, err := json.Marshal(name)
 		if err != nil {
 			return err
 		}
 		e.ws(pos, defPos)
 		e.write(b)
 		e.writeByte(':')

 		if err := e.encode(x.Value); err != nil {
 			return err
 		}
 	}
 	e.writeUnindent('}', endPos, firstPos)
 	return nil
 }

 func compactNewline(pos token.Pos) token.Pos {
 	if pos.RelPos() == token.NewSection {
 		pos = token.Newline.Pos()
 	}
 	return pos
 }

 func foldNewline(pos token.Pos) token.Pos {
 	if pos.RelPos() >= token.Newline {
 		pos = token.Blank.Pos()
 	}
 	return pos
 }
	// Copyright 2020 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 json

	import (
	"bytes"
	"encoding/json"
	"math/big"
	"strings"

	"cuelang.org/go/cue/ast"
	"cuelang.org/go/cue/errors"
	"cuelang.org/go/cue/literal"
	"cuelang.org/go/cue/token"
	"cuelang.org/go/internal/astinternal"
	)

	// Encode converts a CUE AST to JSON.
	//
	// The given file must only contain values that can be directly supported by
	// JSON:
	// Type Restrictions
	// BasicLit
	// File no imports, aliases, or definitions
	// StructLit no embeddings, aliases, or definitions
	// List
	// Field must be regular; label must be a BasicLit or Ident
	//
	// Comments and attributes are ignored.
	func Encode(n ast.Node) (b []byte, err error) {
	e := encoder{}
	err = e.encode(n)
	if err != nil {
	return nil, err
	}
	return e.w.Bytes(), nil
	}

	type encoder struct {
	w bytes.Buffer
	tab []byte
	indentsAtLevel []int
	indenting bool
	unIndenting int
	}

	func (e *encoder) writeIndent(b byte) {
	if e.indenting {
	e.indentsAtLevel[len(e.indentsAtLevel)-1]++
	} else {
	e.indentsAtLevel = append(e.indentsAtLevel, 0)
	}
	e.indenting = true
	_ = e.w.WriteByte(b)
	}

	func (e *encoder) writeUnindent(b byte, pos, def token.Pos) {
	if e.unIndenting > 0 {
	e.unIndenting--
	} else {
	e.unIndenting = e.indentsAtLevel[len(e.indentsAtLevel)-1]
	e.indentsAtLevel = e.indentsAtLevel[:len(e.indentsAtLevel)-1]
	}
	e.indenting = false
	e.ws(pos, def.RelPos())
	_ = e.w.WriteByte(b)
	}

	func (e *encoder) writeString(s string) {
	_, _ = e.w.WriteString(s)
	e.indenting = false
	}

	func (e *encoder) writeByte(b byte) {
	_ = e.w.WriteByte(b)
	}

	func (e *encoder) write(b []byte) {
	_, _ = e.w.Write(b)
	e.indenting = false
	}

	func (e *encoder) indent() {
	for range e.indentsAtLevel {
	e.write(e.tab)
	}
	}

	func (e *encoder) ws(pos token.Pos, default_ token.RelPos) {
	rel := pos.RelPos()
	if pos == token.NoPos {
	rel = default_
	}
	switch rel {
	case token.NoSpace:
	case token.Blank:
	e.writeByte(' ')
	case token.Newline:
	e.writeByte('\n')
	e.indent()
	case token.NewSection:
	e.writeString("\n\n")
	e.indent()
	}
	}
	func (e *encoder) encode(n ast.Node) error {
	if e.tab == nil {
	e.tab = []byte(" ")
	}
	const defPos = token.NoSpace
	switch x := n.(type) {
	case *ast.BasicLit:
	e.ws(x.Pos(), defPos)
	return e.encodeScalar(x, true)

	case *ast.ListLit:
	e.ws(foldNewline(x.Pos()), token.NoRelPos)
	if len(x.Elts) == 0 {
	e.writeString("[]")
	return nil
	}
	e.writeIndent('[')
	for i, x := range x.Elts {
	if i > 0 {
	e.writeString(",")
	}
	if err := e.encode(x); err != nil {
	return err
	}
	}
	e.writeUnindent(']', x.Rbrack, compactNewline(x.Elts[0].Pos()))
	return nil

	case *ast.StructLit:
	e.ws(foldNewline(n.Pos()), token.NoRelPos)
	return e.encodeDecls(x.Elts, x.Rbrace)

	case *ast.File:
	return e.encodeDecls(x.Decls, token.NoPos)

	case *ast.UnaryExpr:
	e.ws(foldNewline(x.Pos()), defPos)
	l, ok := x.X.(*ast.BasicLit)
	if ok && x.Op == token.SUB && (l.Kind == token.INT \|\| l.Kind == token.FLOAT) {
	e.writeByte('-')
	return e.encodeScalar(l, false)
	}
	}
	return errors.Newf(n.Pos(), "json: unsupported node %s (%T)", astinternal.DebugStr(n), n)
	}

	func (e encoder) encodeScalar(l ast.BasicLit, allowMinus bool) error {
	switch l.Kind {
	case token.INT:
	var x big.Int
	return e.setNum(l, allowMinus, &x)

	case token.FLOAT:
	var x big.Float
	return e.setNum(l, allowMinus, &x)

	case token.TRUE:
	e.writeString("true")

	case token.FALSE:
	e.writeString("false")

	case token.NULL:
	e.writeString("null")

	case token.STRING:
	str, err := literal.Unquote(l.Value)
	if err != nil {
	return err
	}
	b, err := json.Marshal(str)
	if err != nil {
	return err
	}
	e.write(b)

	default:
	return errors.Newf(l.Pos(), "unknown literal type %v", l.Kind)
	}
	return nil
	}

	func (e encoder) setNum(l ast.BasicLit, allowMinus bool, x interface{}) error {
	if !allowMinus && strings.HasPrefix(l.Value, "-") {
	return errors.Newf(l.Pos(), "double minus not allowed")
	}
	var ni literal.NumInfo
	if err := literal.ParseNum(l.Value, &ni); err != nil {
	return err
	}
	e.writeString(ni.String())
	return nil
	}

	// encodeDecls converts a sequence of declarations to a value. If it encounters
	// an embedded value, it will return this expression. This is more relaxed for
	// structs than is currently allowed for CUE, but the expectation is that this
	// will be allowed at some point. The input would still be illegal CUE.
	func (e *encoder) encodeDecls(decls []ast.Decl, endPos token.Pos) error {
	var embed ast.Expr
	var fields []*ast.Field

	for _, d := range decls {
	switch x := d.(type) {
	default:
	return errors.Newf(x.Pos(), "json: unsupported node %s (%T)", astinternal.DebugStr(x), x)

	case *ast.Package:
	if embed != nil \|\| fields != nil {
	return errors.Newf(x.Pos(), "invalid package clause")
	}
	continue

	case *ast.Field:
	if x.Token == token.ISA {
	return errors.Newf(x.TokenPos, "json: definition not allowed")
	}
	if x.Optional != token.NoPos {
	return errors.Newf(x.Optional, "json: optional fields not allowed")
	}
	fields = append(fields, x)

	case *ast.EmbedDecl:
	if embed != nil {
	return errors.Newf(x.Pos(), "json: multiple embedded values")
	}
	embed = x.Expr

	case *ast.CommentGroup:
	}
	}

	if embed != nil {
	if fields != nil {
	return errors.Newf(embed.Pos(), "json: embedding mixed with fields")
	}
	return e.encode(embed)
	}

	if len(fields) == 0 {
	e.writeString("{}")
	return nil
	}

	e.writeIndent('{')
	pos := compactNewline(fields[0].Pos())
	if endPos == token.NoPos && pos.RelPos() == token.Blank {
	pos = token.NoPos
	}
	firstPos := pos
	const defPos = token.NoRelPos
	for i, x := range fields {
	if i > 0 {
	e.writeByte(',')
	pos = x.Pos()
	}
	name, _, err := ast.LabelName(x.Label)
	if err != nil {
	return errors.Newf(x.Label.Pos(), "json: only literal labels allowed")
	}
	b, err := json.Marshal(name)
	if err != nil {
	return err
	}
	e.ws(pos, defPos)
	e.write(b)
	e.writeByte(':')

	if err := e.encode(x.Value); err != nil {
	return err
	}
	}
	e.writeUnindent('}', endPos, firstPos)
	return nil
	}

	func compactNewline(pos token.Pos) token.Pos {
	if pos.RelPos() == token.NewSection {
	pos = token.Newline.Pos()
	}
	return pos
	}

	func foldNewline(pos token.Pos) token.Pos {
	if pos.RelPos() >= token.Newline {
	pos = token.Blank.Pos()
	}
	return pos
	}