package parser
import (
"errors"
"fmt"
"github.com/hashicorp/hcl/hcl/ast"
hcltoken "github.com/hashicorp/hcl/hcl/token"
"github.com/hashicorp/hcl/json/scanner"
"github.com/hashicorp/hcl/json/token"
)
type Parser struct {
sc *scanner.Scanner
// Last read token
tok token.Token
commaPrev token.Token
enableTrace bool
indent int
n int // buffer size (max = 1)
}
func newParser(src []byte) *Parser {
return &Parser{
sc: scanner.New(src),
}
}
// Parse returns the fully parsed source and returns the abstract syntax tree.
func Parse(src []byte) (*ast.File, error) {
p := newParser(src)
return p.Parse()
}
var errEofToken = errors.New("EOF token found")
// Parse returns the fully parsed source and returns the abstract syntax tree.
func (p *Parser) Parse() (*ast.File, error) {
f := &ast.File{}
var err, scerr error
p.sc.Error = func(pos token.Pos, msg string) {
scerr = fmt.Errorf("%s: %s", pos, msg)
}
// The root must be an object in JSON
object, err := p.object()
if scerr != nil {
return nil, scerr
}
if err != nil {
return nil, err
}
// We make our final node an object list so it is more HCL compatible
f.Node = object.List
// Flatten it, which finds patterns and turns them into more HCL-like
// AST trees.
flattenObjects(f.Node)
return f, nil
}
func (p *Parser) objectList() (*ast.ObjectList, error) {
defer un(trace(p, "ParseObjectList"))
node := &ast.ObjectList{}
for {
n, err := p.objectItem()
if err == errEofToken {
break // we are finished
}
// we don't return a nil node, because might want to use already
// collected items.
if err != nil {
return node, err
}
node.Add(n)
// Check for a followup comma. If it isn't a comma, then we're done
if tok := p.scan(); tok.Type != token.COMMA {
break
}
}
return node, nil
}
// objectItem parses a single object item
func (p *Parser) objectItem() (*ast.ObjectItem, error) {
defer un(trace(p, "ParseObjectItem"))
keys, err := p.objectKey()
if err != nil {
return nil, err
}
o := &ast.ObjectItem{
Keys: keys,
}
switch p.tok.Type {
case token.COLON:
pos := p.tok.Pos
o.Assign = hcltoken.Pos{
Filename: pos.Filename,
Offset: pos.Offset,
Line: pos.Line,
Column: pos.Column,
}
o.Val, err = p.objectValue()
if err != nil {
return nil, err
}
}
return o, nil
}
// objectKey parses an object key and returns a ObjectKey AST
func (p *Parser) objectKey() ([]*ast.ObjectKey, error) {
keyCount := 0
keys := make([]*ast.ObjectKey, 0)
for {
tok := p.scan()
switch tok.Type {
case token.EOF:
return nil, errEofToken
case token.STRING:
keyCount++
keys = append(keys, &ast.ObjectKey{
Token: p.tok.HCLToken(),
})
case token.COLON:
// If we have a zero keycount it means that we never got
// an object key, i.e. `{ :`. This is a syntax error.
if keyCount == 0 {
return nil, fmt.Errorf("expected: STRING got: %s", p.tok.Type)
}
// Done
return keys, nil
case token.ILLEGAL:
return nil, errors.New("illegal")
default:
return nil, fmt.Errorf("expected: STRING got: %s", p.tok.Type)
}
}
}
// object parses any type of object, such as number, bool, string, object or
// list.
func (p *Parser) objectValue() (ast.Node, error) {
defer un(trace(p, "ParseObjectValue"))
tok := p.scan()
switch tok.Type {
case token.NUMBER, token.FLOAT, token.BOOL, token.NULL, token.STRING:
return p.literalType()
case token.LBRACE:
return p.objectType()
case token.LBRACK:
return p.listType()
case token.EOF:
return nil, errEofToken
}
return nil, fmt.Errorf("Expected object value, got unknown token: %+v", tok)
}
// object parses any type of object, such as number, bool, string, object or
// list.
func (p *Parser) object() (*ast.ObjectType, error) {
defer un(trace(p, "ParseType"))
tok := p.scan()
switch tok.Type {
case token.LBRACE:
return p.objectType()
case token.EOF:
return nil, errEofToken
}
return nil, fmt.Errorf("Expected object, got unknown token: %+v", tok)
}
// objectType parses an object type and returns a ObjectType AST
func (p *Parser) objectType() (*ast.ObjectType, error) {
defer un(trace(p, "ParseObjectType"))
// we assume that the currently scanned token is a LBRACE
o := &ast.ObjectType{}
l, err := p.objectList()
// if we hit RBRACE, we are good to go (means we parsed all Items), if it's
// not a RBRACE, it's an syntax error and we just return it.
if err != nil && p.tok.Type != token.RBRACE {
return nil, err
}
o.List = l
return o, nil
}
// listType parses a list type and returns a ListType AST
func (p *Parser) listType() (*ast.ListType, error) {
defer un(trace(p, "ParseListType"))
// we assume that the currently scanned token is a LBRACK
l := &ast.ListType{}
for {
tok := p.scan()
switch tok.Type {
case token.NUMBER, token.FLOAT, token.STRING:
node, err := p.literalType()
if err != nil {
return nil, err
}
l.Add(node)
case token.COMMA:
continue
case token.LBRACE:
node, err := p.objectType()
if err != nil {
return nil, err
}
l.Add(node)
case token.BOOL:
// TODO(arslan) should we support? not supported by HCL yet
case token.LBRACK:
// TODO(arslan) should we support nested lists? Even though it's
// written in README of HCL, it's not a part of the grammar
// (not defined in parse.y)
case token.RBRACK:
// finished
return l, nil
default:
return nil, fmt.Errorf("unexpected token while parsing list: %s", tok.Type)
}
}
}
// literalType parses a literal type and returns a LiteralType AST
func (p *Parser) literalType() (*ast.LiteralType, error) {
defer un(trace(p, "ParseLiteral"))
return &ast.LiteralType{
Token: p.tok.HCLToken(),
}, nil
}
// scan returns the next token from the underlying scanner. If a token has
// been unscanned then read that instead.
func (p *Parser) scan() token.Token {
// If we have a token on the buffer, then return it.
if p.n != 0 {
p.n = 0
return p.tok
}
p.tok = p.sc.Scan()
return p.tok
}
// unscan pushes the previously read token back onto the buffer.
func (p *Parser) unscan() {
p.n = 1
}
// ----------------------------------------------------------------------------
// Parsing support
func (p *Parser) printTrace(a ...interface{}) {
if !p.enableTrace {
return
}
const dots = ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "
const n = len(dots)
fmt.Printf("%5d:%3d: ", p.tok.Pos.Line, p.tok.Pos.Column)
i := 2 * p.indent
for i > n {
fmt.Print(dots)
i -= n
}
// i <= n
fmt.Print(dots[0:i])
fmt.Println(a...)
}
func trace(p *Parser, msg string) *Parser {
p.printTrace(msg, "(")
p.indent++
return p
}
// Usage pattern: defer un(trace(p, "..."))
func un(p *Parser) {
p.indent--
p.printTrace(")")
}
