hugo

node.go (24824B)

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // Parse nodes.
 
 package parse
 
 import (
 	"fmt"
 	"strconv"
 	"strings"
 )
 
 var textFormat = "%s" // Changed to "%q" in tests for better error messages.
 
 // A Node is an element in the parse tree. The interface is trivial.
 // The interface contains an unexported method so that only
 // types local to this package can satisfy it.
 type Node interface {
 	Type() NodeType
 	String() string
 	// Copy does a deep copy of the Node and all its components.
 	// To avoid type assertions, some XxxNodes also have specialized
 	// CopyXxx methods that return *XxxNode.
 	Copy() Node
 	Position() Pos // byte position of start of node in full original input string
 	// tree returns the containing *Tree.
 	// It is unexported so all implementations of Node are in this package.
 	tree() *Tree
 	// writeTo writes the String output to the builder.
 	writeTo(*strings.Builder)
 }
 
 // NodeType identifies the type of a parse tree node.
 type NodeType int
 
 // Pos represents a byte position in the original input text from which
 // this template was parsed.
 type Pos int
 
 func (p Pos) Position() Pos {
 	return p
 }
 
 // Type returns itself and provides an easy default implementation
 // for embedding in a Node. Embedded in all non-trivial Nodes.
 func (t NodeType) Type() NodeType {
 	return t
 }
 
 const (
 	NodeText       NodeType = iota // Plain text.
 	NodeAction                     // A non-control action such as a field evaluation.
 	NodeBool                       // A boolean constant.
 	NodeChain                      // A sequence of field accesses.
 	NodeCommand                    // An element of a pipeline.
 	NodeDot                        // The cursor, dot.
 	nodeElse                       // An else action. Not added to tree.
 	nodeEnd                        // An end action. Not added to tree.
 	NodeField                      // A field or method name.
 	NodeIdentifier                 // An identifier; always a function name.
 	NodeIf                         // An if action.
 	NodeList                       // A list of Nodes.
 	NodeNil                        // An untyped nil constant.
 	NodeNumber                     // A numerical constant.
 	NodePipe                       // A pipeline of commands.
 	NodeRange                      // A range action.
 	NodeString                     // A string constant.
 	NodeTemplate                   // A template invocation action.
 	NodeVariable                   // A $ variable.
 	NodeWith                       // A with action.
 	NodeComment                    // A comment.
 	NodeBreak                      // A break action.
 	NodeContinue                   // A continue action.
 )
 
 // Nodes.
 
 // ListNode holds a sequence of nodes.
 type ListNode struct {
 	NodeType
 	Pos
 	tr    *Tree
 	Nodes []Node // The element nodes in lexical order.
 }
 
 func (t *Tree) newList(pos Pos) *ListNode {
 	return &ListNode{tr: t, NodeType: NodeList, Pos: pos}
 }
 
 func (l *ListNode) append(n Node) {
 	l.Nodes = append(l.Nodes, n)
 }
 
 func (l *ListNode) tree() *Tree {
 	return l.tr
 }
 
 func (l *ListNode) String() string {
 	var sb strings.Builder
 	l.writeTo(&sb)
 	return sb.String()
 }
 
 func (l *ListNode) writeTo(sb *strings.Builder) {
 	for _, n := range l.Nodes {
 		n.writeTo(sb)
 	}
 }
 
 func (l *ListNode) CopyList() *ListNode {
 	if l == nil {
 		return l
 	}
 	n := l.tr.newList(l.Pos)
 	for _, elem := range l.Nodes {
 		n.append(elem.Copy())
 	}
 	return n
 }
 
 func (l *ListNode) Copy() Node {
 	return l.CopyList()
 }
 
 // TextNode holds plain text.
 type TextNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	Text []byte // The text; may span newlines.
 }
 
 func (t *Tree) newText(pos Pos, text string) *TextNode {
 	return &TextNode{tr: t, NodeType: NodeText, Pos: pos, Text: []byte(text)}
 }
 
 func (t *TextNode) String() string {
 	return fmt.Sprintf(textFormat, t.Text)
 }
 
 func (t *TextNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(t.String())
 }
 
 func (t *TextNode) tree() *Tree {
 	return t.tr
 }
 
 func (t *TextNode) Copy() Node {
 	return &TextNode{tr: t.tr, NodeType: NodeText, Pos: t.Pos, Text: append([]byte{}, t.Text...)}
 }
 
 // CommentNode holds a comment.
 type CommentNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	Text string // Comment text.
 }
 
 func (t *Tree) newComment(pos Pos, text string) *CommentNode {
 	return &CommentNode{tr: t, NodeType: NodeComment, Pos: pos, Text: text}
 }
 
 func (c *CommentNode) String() string {
 	var sb strings.Builder
 	c.writeTo(&sb)
 	return sb.String()
 }
 
 func (c *CommentNode) writeTo(sb *strings.Builder) {
 	sb.WriteString("{{")
 	sb.WriteString(c.Text)
 	sb.WriteString("}}")
 }
 
 func (c *CommentNode) tree() *Tree {
 	return c.tr
 }
 
 func (c *CommentNode) Copy() Node {
 	return &CommentNode{tr: c.tr, NodeType: NodeComment, Pos: c.Pos, Text: c.Text}
 }
 
 // PipeNode holds a pipeline with optional declaration
 type PipeNode struct {
 	NodeType
 	Pos
 	tr       *Tree
 	Line     int             // The line number in the input. Deprecated: Kept for compatibility.
 	IsAssign bool            // The variables are being assigned, not declared.
 	Decl     []*VariableNode // Variables in lexical order.
 	Cmds     []*CommandNode  // The commands in lexical order.
 }
 
 func (t *Tree) newPipeline(pos Pos, line int, vars []*VariableNode) *PipeNode {
 	return &PipeNode{tr: t, NodeType: NodePipe, Pos: pos, Line: line, Decl: vars}
 }
 
 func (p *PipeNode) append(command *CommandNode) {
 	p.Cmds = append(p.Cmds, command)
 }
 
 func (p *PipeNode) String() string {
 	var sb strings.Builder
 	p.writeTo(&sb)
 	return sb.String()
 }
 
 func (p *PipeNode) writeTo(sb *strings.Builder) {
 	if len(p.Decl) > 0 {
 		for i, v := range p.Decl {
 			if i > 0 {
 				sb.WriteString(", ")
 			}
 			v.writeTo(sb)
 		}
 		sb.WriteString(" := ")
 	}
 	for i, c := range p.Cmds {
 		if i > 0 {
 			sb.WriteString(" | ")
 		}
 		c.writeTo(sb)
 	}
 }
 
 func (p *PipeNode) tree() *Tree {
 	return p.tr
 }
 
 func (p *PipeNode) CopyPipe() *PipeNode {
 	if p == nil {
 		return p
 	}
 	vars := make([]*VariableNode, len(p.Decl))
 	for i, d := range p.Decl {
 		vars[i] = d.Copy().(*VariableNode)
 	}
 	n := p.tr.newPipeline(p.Pos, p.Line, vars)
 	n.IsAssign = p.IsAssign
 	for _, c := range p.Cmds {
 		n.append(c.Copy().(*CommandNode))
 	}
 	return n
 }
 
 func (p *PipeNode) Copy() Node {
 	return p.CopyPipe()
 }
 
 // ActionNode holds an action (something bounded by delimiters).
 // Control actions have their own nodes; ActionNode represents simple
 // ones such as field evaluations and parenthesized pipelines.
 type ActionNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	Line int       // The line number in the input. Deprecated: Kept for compatibility.
 	Pipe *PipeNode // The pipeline in the action.
 }
 
 func (t *Tree) newAction(pos Pos, line int, pipe *PipeNode) *ActionNode {
 	return &ActionNode{tr: t, NodeType: NodeAction, Pos: pos, Line: line, Pipe: pipe}
 }
 
 func (a *ActionNode) String() string {
 	var sb strings.Builder
 	a.writeTo(&sb)
 	return sb.String()
 }
 
 func (a *ActionNode) writeTo(sb *strings.Builder) {
 	sb.WriteString("{{")
 	a.Pipe.writeTo(sb)
 	sb.WriteString("}}")
 }
 
 func (a *ActionNode) tree() *Tree {
 	return a.tr
 }
 
 func (a *ActionNode) Copy() Node {
 	return a.tr.newAction(a.Pos, a.Line, a.Pipe.CopyPipe())
 
 }
 
 // CommandNode holds a command (a pipeline inside an evaluating action).
 type CommandNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	Args []Node // Arguments in lexical order: Identifier, field, or constant.
 }
 
 func (t *Tree) newCommand(pos Pos) *CommandNode {
 	return &CommandNode{tr: t, NodeType: NodeCommand, Pos: pos}
 }
 
 func (c *CommandNode) append(arg Node) {
 	c.Args = append(c.Args, arg)
 }
 
 func (c *CommandNode) String() string {
 	var sb strings.Builder
 	c.writeTo(&sb)
 	return sb.String()
 }
 
 func (c *CommandNode) writeTo(sb *strings.Builder) {
 	for i, arg := range c.Args {
 		if i > 0 {
 			sb.WriteByte(' ')
 		}
 		if arg, ok := arg.(*PipeNode); ok {
 			sb.WriteByte('(')
 			arg.writeTo(sb)
 			sb.WriteByte(')')
 			continue
 		}
 		arg.writeTo(sb)
 	}
 }
 
 func (c *CommandNode) tree() *Tree {
 	return c.tr
 }
 
 func (c *CommandNode) Copy() Node {
 	if c == nil {
 		return c
 	}
 	n := c.tr.newCommand(c.Pos)
 	for _, c := range c.Args {
 		n.append(c.Copy())
 	}
 	return n
 }
 
 // IdentifierNode holds an identifier.
 type IdentifierNode struct {
 	NodeType
 	Pos
 	tr    *Tree
 	Ident string // The identifier's name.
 }
 
 // NewIdentifier returns a new IdentifierNode with the given identifier name.
 func NewIdentifier(ident string) *IdentifierNode {
 	return &IdentifierNode{NodeType: NodeIdentifier, Ident: ident}
 }
 
 // SetPos sets the position. NewIdentifier is a public method so we can't modify its signature.
 // Chained for convenience.
 // TODO: fix one day?
 func (i *IdentifierNode) SetPos(pos Pos) *IdentifierNode {
 	i.Pos = pos
 	return i
 }
 
 // SetTree sets the parent tree for the node. NewIdentifier is a public method so we can't modify its signature.
 // Chained for convenience.
 // TODO: fix one day?
 func (i *IdentifierNode) SetTree(t *Tree) *IdentifierNode {
 	i.tr = t
 	return i
 }
 
 func (i *IdentifierNode) String() string {
 	return i.Ident
 }
 
 func (i *IdentifierNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(i.String())
 }
 
 func (i *IdentifierNode) tree() *Tree {
 	return i.tr
 }
 
 func (i *IdentifierNode) Copy() Node {
 	return NewIdentifier(i.Ident).SetTree(i.tr).SetPos(i.Pos)
 }
 
 // VariableNode holds a list of variable names, possibly with chained field
 // accesses. The dollar sign is part of the (first) name.
 type VariableNode struct {
 	NodeType
 	Pos
 	tr    *Tree
 	Ident []string // Variable name and fields in lexical order.
 }
 
 func (t *Tree) newVariable(pos Pos, ident string) *VariableNode {
 	return &VariableNode{tr: t, NodeType: NodeVariable, Pos: pos, Ident: strings.Split(ident, ".")}
 }
 
 func (v *VariableNode) String() string {
 	var sb strings.Builder
 	v.writeTo(&sb)
 	return sb.String()
 }
 
 func (v *VariableNode) writeTo(sb *strings.Builder) {
 	for i, id := range v.Ident {
 		if i > 0 {
 			sb.WriteByte('.')
 		}
 		sb.WriteString(id)
 	}
 }
 
 func (v *VariableNode) tree() *Tree {
 	return v.tr
 }
 
 func (v *VariableNode) Copy() Node {
 	return &VariableNode{tr: v.tr, NodeType: NodeVariable, Pos: v.Pos, Ident: append([]string{}, v.Ident...)}
 }
 
 // DotNode holds the special identifier '.'.
 type DotNode struct {
 	NodeType
 	Pos
 	tr *Tree
 }
 
 func (t *Tree) newDot(pos Pos) *DotNode {
 	return &DotNode{tr: t, NodeType: NodeDot, Pos: pos}
 }
 
 func (d *DotNode) Type() NodeType {
 	// Override method on embedded NodeType for API compatibility.
 	// TODO: Not really a problem; could change API without effect but
 	// api tool complains.
 	return NodeDot
 }
 
 func (d *DotNode) String() string {
 	return "."
 }
 
 func (d *DotNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(d.String())
 }
 
 func (d *DotNode) tree() *Tree {
 	return d.tr
 }
 
 func (d *DotNode) Copy() Node {
 	return d.tr.newDot(d.Pos)
 }
 
 // NilNode holds the special identifier 'nil' representing an untyped nil constant.
 type NilNode struct {
 	NodeType
 	Pos
 	tr *Tree
 }
 
 func (t *Tree) newNil(pos Pos) *NilNode {
 	return &NilNode{tr: t, NodeType: NodeNil, Pos: pos}
 }
 
 func (n *NilNode) Type() NodeType {
 	// Override method on embedded NodeType for API compatibility.
 	// TODO: Not really a problem; could change API without effect but
 	// api tool complains.
 	return NodeNil
 }
 
 func (n *NilNode) String() string {
 	return "nil"
 }
 
 func (n *NilNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(n.String())
 }
 
 func (n *NilNode) tree() *Tree {
 	return n.tr
 }
 
 func (n *NilNode) Copy() Node {
 	return n.tr.newNil(n.Pos)
 }
 
 // FieldNode holds a field (identifier starting with '.').
 // The names may be chained ('.x.y').
 // The period is dropped from each ident.
 type FieldNode struct {
 	NodeType
 	Pos
 	tr    *Tree
 	Ident []string // The identifiers in lexical order.
 }
 
 func (t *Tree) newField(pos Pos, ident string) *FieldNode {
 	return &FieldNode{tr: t, NodeType: NodeField, Pos: pos, Ident: strings.Split(ident[1:], ".")} // [1:] to drop leading period
 }
 
 func (f *FieldNode) String() string {
 	var sb strings.Builder
 	f.writeTo(&sb)
 	return sb.String()
 }
 
 func (f *FieldNode) writeTo(sb *strings.Builder) {
 	for _, id := range f.Ident {
 		sb.WriteByte('.')
 		sb.WriteString(id)
 	}
 }
 
 func (f *FieldNode) tree() *Tree {
 	return f.tr
 }
 
 func (f *FieldNode) Copy() Node {
 	return &FieldNode{tr: f.tr, NodeType: NodeField, Pos: f.Pos, Ident: append([]string{}, f.Ident...)}
 }
 
 // ChainNode holds a term followed by a chain of field accesses (identifier starting with '.').
 // The names may be chained ('.x.y').
 // The periods are dropped from each ident.
 type ChainNode struct {
 	NodeType
 	Pos
 	tr    *Tree
 	Node  Node
 	Field []string // The identifiers in lexical order.
 }
 
 func (t *Tree) newChain(pos Pos, node Node) *ChainNode {
 	return &ChainNode{tr: t, NodeType: NodeChain, Pos: pos, Node: node}
 }
 
 // Add adds the named field (which should start with a period) to the end of the chain.
 func (c *ChainNode) Add(field string) {
 	if len(field) == 0 || field[0] != '.' {
 		panic("no dot in field")
 	}
 	field = field[1:] // Remove leading dot.
 	if field == "" {
 		panic("empty field")
 	}
 	c.Field = append(c.Field, field)
 }
 
 func (c *ChainNode) String() string {
 	var sb strings.Builder
 	c.writeTo(&sb)
 	return sb.String()
 }
 
 func (c *ChainNode) writeTo(sb *strings.Builder) {
 	if _, ok := c.Node.(*PipeNode); ok {
 		sb.WriteByte('(')
 		c.Node.writeTo(sb)
 		sb.WriteByte(')')
 	} else {
 		c.Node.writeTo(sb)
 	}
 	for _, field := range c.Field {
 		sb.WriteByte('.')
 		sb.WriteString(field)
 	}
 }
 
 func (c *ChainNode) tree() *Tree {
 	return c.tr
 }
 
 func (c *ChainNode) Copy() Node {
 	return &ChainNode{tr: c.tr, NodeType: NodeChain, Pos: c.Pos, Node: c.Node, Field: append([]string{}, c.Field...)}
 }
 
 // BoolNode holds a boolean constant.
 type BoolNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	True bool // The value of the boolean constant.
 }
 
 func (t *Tree) newBool(pos Pos, true bool) *BoolNode {
 	return &BoolNode{tr: t, NodeType: NodeBool, Pos: pos, True: true}
 }
 
 func (b *BoolNode) String() string {
 	if b.True {
 		return "true"
 	}
 	return "false"
 }
 
 func (b *BoolNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(b.String())
 }
 
 func (b *BoolNode) tree() *Tree {
 	return b.tr
 }
 
 func (b *BoolNode) Copy() Node {
 	return b.tr.newBool(b.Pos, b.True)
 }
 
 // NumberNode holds a number: signed or unsigned integer, float, or complex.
 // The value is parsed and stored under all the types that can represent the value.
 // This simulates in a small amount of code the behavior of Go's ideal constants.
 type NumberNode struct {
 	NodeType
 	Pos
 	tr         *Tree
 	IsInt      bool       // Number has an integral value.
 	IsUint     bool       // Number has an unsigned integral value.
 	IsFloat    bool       // Number has a floating-point value.
 	IsComplex  bool       // Number is complex.
 	Int64      int64      // The signed integer value.
 	Uint64     uint64     // The unsigned integer value.
 	Float64    float64    // The floating-point value.
 	Complex128 complex128 // The complex value.
 	Text       string     // The original textual representation from the input.
 }
 
 func (t *Tree) newNumber(pos Pos, text string, typ itemType) (*NumberNode, error) {
 	n := &NumberNode{tr: t, NodeType: NodeNumber, Pos: pos, Text: text}
 	switch typ {
 	case itemCharConstant:
 		rune, _, tail, err := strconv.UnquoteChar(text[1:], text[0])
 		if err != nil {
 			return nil, err
 		}
 		if tail != "'" {
 			return nil, fmt.Errorf("malformed character constant: %s", text)
 		}
 		n.Int64 = int64(rune)
 		n.IsInt = true
 		n.Uint64 = uint64(rune)
 		n.IsUint = true
 		n.Float64 = float64(rune) // odd but those are the rules.
 		n.IsFloat = true
 		return n, nil
 	case itemComplex:
 		// fmt.Sscan can parse the pair, so let it do the work.
 		if _, err := fmt.Sscan(text, &n.Complex128); err != nil {
 			return nil, err
 		}
 		n.IsComplex = true
 		n.simplifyComplex()
 		return n, nil
 	}
 	// Imaginary constants can only be complex unless they are zero.
 	if len(text) > 0 && text[len(text)-1] == 'i' {
 		f, err := strconv.ParseFloat(text[:len(text)-1], 64)
 		if err == nil {
 			n.IsComplex = true
 			n.Complex128 = complex(0, f)
 			n.simplifyComplex()
 			return n, nil
 		}
 	}
 	// Do integer test first so we get 0x123 etc.
 	u, err := strconv.ParseUint(text, 0, 64) // will fail for -0; fixed below.
 	if err == nil {
 		n.IsUint = true
 		n.Uint64 = u
 	}
 	i, err := strconv.ParseInt(text, 0, 64)
 	if err == nil {
 		n.IsInt = true
 		n.Int64 = i
 		if i == 0 {
 			n.IsUint = true // in case of -0.
 			n.Uint64 = u
 		}
 	}
 	// If an integer extraction succeeded, promote the float.
 	if n.IsInt {
 		n.IsFloat = true
 		n.Float64 = float64(n.Int64)
 	} else if n.IsUint {
 		n.IsFloat = true
 		n.Float64 = float64(n.Uint64)
 	} else {
 		f, err := strconv.ParseFloat(text, 64)
 		if err == nil {
 			// If we parsed it as a float but it looks like an integer,
 			// it's a huge number too large to fit in an int. Reject it.
 			if !strings.ContainsAny(text, ".eEpP") {
 				return nil, fmt.Errorf("integer overflow: %q", text)
 			}
 			n.IsFloat = true
 			n.Float64 = f
 			// If a floating-point extraction succeeded, extract the int if needed.
 			if !n.IsInt && float64(int64(f)) == f {
 				n.IsInt = true
 				n.Int64 = int64(f)
 			}
 			if !n.IsUint && float64(uint64(f)) == f {
 				n.IsUint = true
 				n.Uint64 = uint64(f)
 			}
 		}
 	}
 	if !n.IsInt && !n.IsUint && !n.IsFloat {
 		return nil, fmt.Errorf("illegal number syntax: %q", text)
 	}
 	return n, nil
 }
 
 // simplifyComplex pulls out any other types that are represented by the complex number.
 // These all require that the imaginary part be zero.
 func (n *NumberNode) simplifyComplex() {
 	n.IsFloat = imag(n.Complex128) == 0
 	if n.IsFloat {
 		n.Float64 = real(n.Complex128)
 		n.IsInt = float64(int64(n.Float64)) == n.Float64
 		if n.IsInt {
 			n.Int64 = int64(n.Float64)
 		}
 		n.IsUint = float64(uint64(n.Float64)) == n.Float64
 		if n.IsUint {
 			n.Uint64 = uint64(n.Float64)
 		}
 	}
 }
 
 func (n *NumberNode) String() string {
 	return n.Text
 }
 
 func (n *NumberNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(n.String())
 }
 
 func (n *NumberNode) tree() *Tree {
 	return n.tr
 }
 
 func (n *NumberNode) Copy() Node {
 	nn := new(NumberNode)
 	*nn = *n // Easy, fast, correct.
 	return nn
 }
 
 // StringNode holds a string constant. The value has been "unquoted".
 type StringNode struct {
 	NodeType
 	Pos
 	tr     *Tree
 	Quoted string // The original text of the string, with quotes.
 	Text   string // The string, after quote processing.
 }
 
 func (t *Tree) newString(pos Pos, orig, text string) *StringNode {
 	return &StringNode{tr: t, NodeType: NodeString, Pos: pos, Quoted: orig, Text: text}
 }
 
 func (s *StringNode) String() string {
 	return s.Quoted
 }
 
 func (s *StringNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(s.String())
 }
 
 func (s *StringNode) tree() *Tree {
 	return s.tr
 }
 
 func (s *StringNode) Copy() Node {
 	return s.tr.newString(s.Pos, s.Quoted, s.Text)
 }
 
 // endNode represents an {{end}} action.
 // It does not appear in the final parse tree.
 type endNode struct {
 	NodeType
 	Pos
 	tr *Tree
 }
 
 func (t *Tree) newEnd(pos Pos) *endNode {
 	return &endNode{tr: t, NodeType: nodeEnd, Pos: pos}
 }
 
 func (e *endNode) String() string {
 	return "{{end}}"
 }
 
 func (e *endNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(e.String())
 }
 
 func (e *endNode) tree() *Tree {
 	return e.tr
 }
 
 func (e *endNode) Copy() Node {
 	return e.tr.newEnd(e.Pos)
 }
 
 // elseNode represents an {{else}} action. Does not appear in the final tree.
 type elseNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	Line int // The line number in the input. Deprecated: Kept for compatibility.
 }
 
 func (t *Tree) newElse(pos Pos, line int) *elseNode {
 	return &elseNode{tr: t, NodeType: nodeElse, Pos: pos, Line: line}
 }
 
 func (e *elseNode) Type() NodeType {
 	return nodeElse
 }
 
 func (e *elseNode) String() string {
 	return "{{else}}"
 }
 
 func (e *elseNode) writeTo(sb *strings.Builder) {
 	sb.WriteString(e.String())
 }
 
 func (e *elseNode) tree() *Tree {
 	return e.tr
 }
 
 func (e *elseNode) Copy() Node {
 	return e.tr.newElse(e.Pos, e.Line)
 }
 
 // BranchNode is the common representation of if, range, and with.
 type BranchNode struct {
 	NodeType
 	Pos
 	tr       *Tree
 	Line     int       // The line number in the input. Deprecated: Kept for compatibility.
 	Pipe     *PipeNode // The pipeline to be evaluated.
 	List     *ListNode // What to execute if the value is non-empty.
 	ElseList *ListNode // What to execute if the value is empty (nil if absent).
 }
 
 func (b *BranchNode) String() string {
 	var sb strings.Builder
 	b.writeTo(&sb)
 	return sb.String()
 }
 
 func (b *BranchNode) writeTo(sb *strings.Builder) {
 	name := ""
 	switch b.NodeType {
 	case NodeIf:
 		name = "if"
 	case NodeRange:
 		name = "range"
 	case NodeWith:
 		name = "with"
 	default:
 		panic("unknown branch type")
 	}
 	sb.WriteString("{{")
 	sb.WriteString(name)
 	sb.WriteByte(' ')
 	b.Pipe.writeTo(sb)
 	sb.WriteString("}}")
 	b.List.writeTo(sb)
 	if b.ElseList != nil {
 		sb.WriteString("{{else}}")
 		b.ElseList.writeTo(sb)
 	}
 	sb.WriteString("{{end}}")
 }
 
 func (b *BranchNode) tree() *Tree {
 	return b.tr
 }
 
 func (b *BranchNode) Copy() Node {
 	switch b.NodeType {
 	case NodeIf:
 		return b.tr.newIf(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
 	case NodeRange:
 		return b.tr.newRange(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
 	case NodeWith:
 		return b.tr.newWith(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
 	default:
 		panic("unknown branch type")
 	}
 }
 
 // IfNode represents an {{if}} action and its commands.
 type IfNode struct {
 	BranchNode
 }
 
 func (t *Tree) newIf(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *IfNode {
 	return &IfNode{BranchNode{tr: t, NodeType: NodeIf, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
 }
 
 func (i *IfNode) Copy() Node {
 	return i.tr.newIf(i.Pos, i.Line, i.Pipe.CopyPipe(), i.List.CopyList(), i.ElseList.CopyList())
 }
 
 // BreakNode represents a {{break}} action.
 type BreakNode struct {
 	tr *Tree
 	NodeType
 	Pos
 	Line int
 }
 
 func (t *Tree) newBreak(pos Pos, line int) *BreakNode {
 	return &BreakNode{tr: t, NodeType: NodeBreak, Pos: pos, Line: line}
 }
 
 func (b *BreakNode) Copy() Node                  { return b.tr.newBreak(b.Pos, b.Line) }
 func (b *BreakNode) String() string              { return "{{break}}" }
 func (b *BreakNode) tree() *Tree                 { return b.tr }
 func (b *BreakNode) writeTo(sb *strings.Builder) { sb.WriteString("{{break}}") }
 
 // ContinueNode represents a {{continue}} action.
 type ContinueNode struct {
 	tr *Tree
 	NodeType
 	Pos
 	Line int
 }
 
 func (t *Tree) newContinue(pos Pos, line int) *ContinueNode {
 	return &ContinueNode{tr: t, NodeType: NodeContinue, Pos: pos, Line: line}
 }
 
 func (c *ContinueNode) Copy() Node                  { return c.tr.newContinue(c.Pos, c.Line) }
 func (c *ContinueNode) String() string              { return "{{continue}}" }
 func (c *ContinueNode) tree() *Tree                 { return c.tr }
 func (c *ContinueNode) writeTo(sb *strings.Builder) { sb.WriteString("{{continue}}") }
 
 // RangeNode represents a {{range}} action and its commands.
 type RangeNode struct {
 	BranchNode
 }
 
 func (t *Tree) newRange(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *RangeNode {
 	return &RangeNode{BranchNode{tr: t, NodeType: NodeRange, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
 }
 
 func (r *RangeNode) Copy() Node {
 	return r.tr.newRange(r.Pos, r.Line, r.Pipe.CopyPipe(), r.List.CopyList(), r.ElseList.CopyList())
 }
 
 // WithNode represents a {{with}} action and its commands.
 type WithNode struct {
 	BranchNode
 }
 
 func (t *Tree) newWith(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *WithNode {
 	return &WithNode{BranchNode{tr: t, NodeType: NodeWith, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
 }
 
 func (w *WithNode) Copy() Node {
 	return w.tr.newWith(w.Pos, w.Line, w.Pipe.CopyPipe(), w.List.CopyList(), w.ElseList.CopyList())
 }
 
 // TemplateNode represents a {{template}} action.
 type TemplateNode struct {
 	NodeType
 	Pos
 	tr   *Tree
 	Line int       // The line number in the input. Deprecated: Kept for compatibility.
 	Name string    // The name of the template (unquoted).
 	Pipe *PipeNode // The command to evaluate as dot for the template.
 }
 
 func (t *Tree) newTemplate(pos Pos, line int, name string, pipe *PipeNode) *TemplateNode {
 	return &TemplateNode{tr: t, NodeType: NodeTemplate, Pos: pos, Line: line, Name: name, Pipe: pipe}
 }
 
 func (t *TemplateNode) String() string {
 	var sb strings.Builder
 	t.writeTo(&sb)
 	return sb.String()
 }
 
 func (t *TemplateNode) writeTo(sb *strings.Builder) {
 	sb.WriteString("{{template ")
 	sb.WriteString(strconv.Quote(t.Name))
 	if t.Pipe != nil {
 		sb.WriteByte(' ')
 		t.Pipe.writeTo(sb)
 	}
 	sb.WriteString("}}")
 }
 
 func (t *TemplateNode) tree() *Tree {
 	return t.tr
 }
 
 func (t *TemplateNode) Copy() Node {
 	return t.tr.newTemplate(t.Pos, t.Line, t.Name, t.Pipe.CopyPipe())
 }