parser: improve node parsing, remove string() and many other small fixes

parser/ast.go

@@ -5,7 +5,6 @@ import "github.com/fatih/hcl/scanner"
 // Node is an element in the abstract syntax tree.
 type Node interface {
 	node()
-	String() string
 	Pos() scanner.Pos
 }
 
@@ -28,15 +27,6 @@ func (s *Source) add(node Node) {
 	s.nodes = append(s.nodes, node)
 }
 
-func (s *Source) String() string {
-	buf := ""
-	for _, n := range s.nodes {
-		buf += n.String()
-	}
-
-	return buf
-}
-
 func (s *Source) Pos() scanner.Pos {
 	// always returns the uninitiliazed position
 	return s.nodes[0].Pos()
@@ -47,10 +37,6 @@ type Ident struct {
 	token scanner.Token
 }
 
-func (i *Ident) String() string {
-	return i.token.Text
-}
-
 func (i *Ident) Pos() scanner.Pos {
 	return i.token.Pos
 }
@@ -62,10 +48,6 @@ type AssignStatement struct {
 	assign scanner.Pos // position of "="
 }
 
-func (a *AssignStatement) String() string {
-	return a.lhs.String() + " = " + a.rhs.String()
-}
-
 func (a *AssignStatement) Pos() scanner.Pos {
 	return a.lhs.Pos()
 }
@@ -76,20 +58,6 @@ type ObjectStatement struct {
 	ObjectType
 }
 
-func (o *ObjectStatement) String() string {
-	s := ""
-
-	for i, n := range o.Idents {
-		s += n.String()
-		if i != len(o.Idents) {
-			s += " "
-		}
-	}
-
-	s += o.ObjectType.String()
-	return s
-}
-
 func (o *ObjectStatement) Pos() scanner.Pos {
 	return o.Idents[0].Pos()
 }
@@ -97,7 +65,7 @@ func (o *ObjectStatement) Pos() scanner.Pos {
 // LiteralType represents a literal of basic type. Valid types are:
 // scanner.NUMBER, scanner.FLOAT, scanner.BOOL and scanner.STRING
 type LiteralType struct {
-	*Ident
+	token scanner.Token
 }
 
 // isValid() returns true if the underlying identifier satisfies one of the
@@ -111,6 +79,10 @@ func (l *LiteralType) isValid() bool {
 	}
 }
 
+func (l *LiteralType) Pos() scanner.Pos {
+	return l.token.Pos
+}
+
 // ListStatement represents a HCL List type
 type ListType struct {
 	lbrack scanner.Pos // position of "["
@@ -118,16 +90,6 @@ type ListType struct {
 	list   []Node      // the elements in lexical order
 }
 
-func (l *ListType) String() string {
-	s := "[\n"
-	for _, n := range l.list {
-		s += n.String() + ",\n"
-	}
-
-	s += "]"
-	return s
-}
-
 func (l *ListType) Pos() scanner.Pos {
 	return l.lbrack
 }
@@ -139,16 +101,6 @@ type ObjectType struct {
 	list   []Node      // the nodes in lexical order
 }
 
-func (b *ObjectType) String() string {
-	s := "{\n"
-	for _, n := range b.list {
-		s += n.String() + "\n"
-	}
-
-	s += "}"
-	return s
-}
-
 func (b *ObjectType) Pos() scanner.Pos {
 	return b.lbrace
 }

parser/parser.go

@@ -24,6 +24,8 @@ func New(src []byte) *Parser {
 	}
 }
 
+var errEofToken = errors.New("EOF token found")
+
 // Parse returns the fully parsed source and returns the abstract syntax tree.
 func (p *Parser) Parse() (Node, error) {
 	defer un(trace(p, "ParseSource"))
@@ -31,16 +33,15 @@ func (p *Parser) Parse() (Node, error) {
 
 	for {
 		n, err := p.parseNode()
+		if err == errEofToken {
+			break // we are finished
+		}
 		if err != nil {
 			return nil, err
 		}
 
+		// we successfully parsed a node, add it to the final source node
 		node.add(n)
-
-		// break if we hit the end
-		if p.tok.Type == scanner.EOF {
-			break
-		}
 	}
 
 	return node, nil
@@ -50,24 +51,33 @@ func (p *Parser) parseNode() (Node, error) {
 	defer un(trace(p, "ParseNode"))
 
 	tok := p.scan()
-
 	fmt.Println(tok) // debug
 
-	if tok.Type.IsLiteral() {
-		if p.prevTok.Type.IsLiteral() {
+	switch tok.Type {
+	case scanner.ASSIGN:
+		return p.parseAssignment()
+	case scanner.LBRACK:
+		// return p.parseListType()
+	case scanner.LBRACE:
+		// return p.parseObjectTpe()
+	case scanner.COMMENT:
+		// implement comment
+	case scanner.EOF:
+		return nil, errEofToken
+	}
+
+	if tok.Type.IsIdentifier() {
+		if p.prevTok.Type.IsIdentifier() {
 			return p.parseObjectStatement()
 		}
 
-		tok := p.scan()
-		if tok.Type == scanner.ASSIGN {
-			return p.parseAssignment()
+		if tok.Type.IsLiteral() {
+			return p.parseLiteralType()
 		}
-
-		p.unscan()
 		return p.parseIdent()
 	}
 
-	return nil, errors.New("not yet implemented")
+	return nil, fmt.Errorf("not yet implemented: %s", tok.Type)
 }
 
 // parseAssignment parses an assignment and returns a AssignStatement AST
@@ -93,10 +103,6 @@ func (p *Parser) parseAssignment() (*AssignStatement, error) {
 func (p *Parser) parseIdent() (*Ident, error) {
 	defer un(trace(p, "ParseIdent"))
 
-	if !p.tok.Type.IsLiteral() {
-		return nil, errors.New("can't parse non literal token")
-	}
-
 	return &Ident{
 		token: p.tok,
 	}, nil
@@ -104,24 +110,18 @@ func (p *Parser) parseIdent() (*Ident, error) {
 
 // parseLiteralType parses a literal type and returns a LiteralType AST
 func (p *Parser) parseLiteralType() (*LiteralType, error) {
-	i, err := p.parseIdent()
-	if err != nil {
-		return nil, err
-	}
+	defer un(trace(p, "ParseLiteral"))
 
-	l := &LiteralType{}
-	l.Ident = i
-
-	if !l.isValid() {
-		return nil, fmt.Errorf("Identifier is not a LiteralType: %s", l.token)
-	}
-
-	return l, nil
+	return &LiteralType{
+		token: p.tok,
+	}, nil
 }
 
 // parseObjectStatement parses an object statement returns an ObjectStatement
 // AST. ObjectsStatements represents both normal and nested objects statement
 func (p *Parser) parseObjectStatement() (*ObjectStatement, error) {
+	defer un(trace(p, "ParseObjectStatement"))
+
 	return nil, errors.New("ObjectStatement is not implemented yet")
 }
 

parser/parser_test.go

@@ -11,12 +11,7 @@ func TestAssignStatement(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if n.String() != src {
-		t.Errorf("AssignStatement is not parsed correctly\n\twant: '%s'\n\tgot : '%s'", src, n.String())
-	}
-
 	if n.Pos().Line != 1 {
 		t.Errorf("AssignStatement position is wrong\n\twant: '%d'\n\tgot : '%d'", 1, n.Pos().Line)
 	}
-
 }

scanner/token.go

@@ -21,13 +21,15 @@ const (
 	EOF
 	COMMENT
 
-	literal_beg
+	identifier_beg
 	IDENT // literals
+	literal_beg
 	NUMBER // 12345
 	FLOAT  // 123.45
 	BOOL   // true,false
 	STRING // "abc"
 	literal_end
+	identifier_end
 
 	operator_beg
 	LBRACK // [
@@ -81,8 +83,12 @@ func (t TokenType) String() string {
 	return s
 }
 
-// IsLiteral returns true for tokens corresponding to identifiers and basic
+// IsIdentifier returns true for tokens corresponding to identifiers and basic
 // type literals; it returns false otherwise.
+func (t TokenType) IsIdentifier() bool { return identifier_beg < t && t < identifier_end }
+
+// IsLiteral returns true for tokens corresponding to basic type literals; it
+// returns false otherwise.
 func (t TokenType) IsLiteral() bool { return literal_beg < t && t < literal_end }
 
 // IsOperator returns true for tokens corresponding to operators and