node.go

Documentation: text/template/parse

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Parse nodes.
     6  
     7  package parse
     8  
     9  import (
    10  	"bytes"
    11  	"fmt"
    12  	"strconv"
    13  	"strings"
    14  )
    15  
    16  var textFormat = "%s" // Changed to "%q" in tests for better error messages.
    17  
    18  // A Node is an element in the parse tree. The interface is trivial.
    19  // The interface contains an unexported method so that only
    20  // types local to this package can satisfy it.
    21  type Node interface {
    22  	Type() NodeType
    23  	String() string
    24  	// Copy does a deep copy of the Node and all its components.
    25  	// To avoid type assertions, some XxxNodes also have specialized
    26  	// CopyXxx methods that return *XxxNode.
    27  	Copy() Node
    28  	Position() Pos // byte position of start of node in full original input string
    29  	// tree returns the containing *Tree.
    30  	// It is unexported so all implementations of Node are in this package.
    31  	tree() *Tree
    32  }
    33  
    34  // NodeType identifies the type of a parse tree node.
    35  type NodeType int
    36  
    37  // Pos represents a byte position in the original input text from which
    38  // this template was parsed.
    39  type Pos int
    40  
    41  func (p Pos) Position() Pos {
    42  	return p
    43  }
    44  
    45  // Type returns itself and provides an easy default implementation
    46  // for embedding in a Node. Embedded in all non-trivial Nodes.
    47  func (t NodeType) Type() NodeType {
    48  	return t
    49  }
    50  
    51  const (
    52  	NodeText       NodeType = iota // Plain text.
    53  	NodeAction                     // A non-control action such as a field evaluation.
    54  	NodeBool                       // A boolean constant.
    55  	NodeChain                      // A sequence of field accesses.
    56  	NodeCommand                    // An element of a pipeline.
    57  	NodeDot                        // The cursor, dot.
    58  	nodeElse                       // An else action. Not added to tree.
    59  	nodeEnd                        // An end action. Not added to tree.
    60  	NodeField                      // A field or method name.
    61  	NodeIdentifier                 // An identifier; always a function name.
    62  	NodeIf                         // An if action.
    63  	NodeList                       // A list of Nodes.
    64  	NodeNil                        // An untyped nil constant.
    65  	NodeNumber                     // A numerical constant.
    66  	NodePipe                       // A pipeline of commands.
    67  	NodeRange                      // A range action.
    68  	NodeString                     // A string constant.
    69  	NodeTemplate                   // A template invocation action.
    70  	NodeVariable                   // A $ variable.
    71  	NodeWith                       // A with action.
    72  )
    73  
    74  // Nodes.
    75  
    76  // ListNode holds a sequence of nodes.
    77  type ListNode struct {
    78  	NodeType
    79  	Pos
    80  	tr    *Tree
    81  	Nodes []Node // The element nodes in lexical order.
    82  }
    83  
    84  func (t *Tree) newList(pos Pos) *ListNode {
    85  	return &ListNode{tr: t, NodeType: NodeList, Pos: pos}
    86  }
    87  
    88  func (l *ListNode) append(n Node) {
    89  	l.Nodes = append(l.Nodes, n)
    90  }
    91  
    92  func (l *ListNode) tree() *Tree {
    93  	return l.tr
    94  }
    95  
    96  func (l *ListNode) String() string {
    97  	b := new(bytes.Buffer)
    98  	for _, n := range l.Nodes {
    99  		fmt.Fprint(b, n)
   100  	}
   101  	return b.String()
   102  }
   103  
   104  func (l *ListNode) CopyList() *ListNode {
   105  	if l == nil {
   106  		return l
   107  	}
   108  	n := l.tr.newList(l.Pos)
   109  	for _, elem := range l.Nodes {
   110  		n.append(elem.Copy())
   111  	}
   112  	return n
   113  }
   114  
   115  func (l *ListNode) Copy() Node {
   116  	return l.CopyList()
   117  }
   118  
   119  // TextNode holds plain text.
   120  type TextNode struct {
   121  	NodeType
   122  	Pos
   123  	tr   *Tree
   124  	Text []byte // The text; may span newlines.
   125  }
   126  
   127  func (t *Tree) newText(pos Pos, text string) *TextNode {
   128  	return &TextNode{tr: t, NodeType: NodeText, Pos: pos, Text: []byte(text)}
   129  }
   130  
   131  func (t *TextNode) String() string {
   132  	return fmt.Sprintf(textFormat, t.Text)
   133  }
   134  
   135  func (t *TextNode) tree() *Tree {
   136  	return t.tr
   137  }
   138  
   139  func (t *TextNode) Copy() Node {
   140  	return &TextNode{tr: t.tr, NodeType: NodeText, Pos: t.Pos, Text: append([]byte{}, t.Text...)}
   141  }
   142  
   143  // PipeNode holds a pipeline with optional declaration
   144  type PipeNode struct {
   145  	NodeType
   146  	Pos
   147  	tr   *Tree
   148  	Line int             // The line number in the input. Deprecated: Kept for compatibility.
   149  	Decl []*VariableNode // Variable declarations in lexical order.
   150  	Cmds []*CommandNode  // The commands in lexical order.
   151  }
   152  
   153  func (t *Tree) newPipeline(pos Pos, line int, decl []*VariableNode) *PipeNode {
   154  	return &PipeNode{tr: t, NodeType: NodePipe, Pos: pos, Line: line, Decl: decl}
   155  }
   156  
   157  func (p *PipeNode) append(command *CommandNode) {
   158  	p.Cmds = append(p.Cmds, command)
   159  }
   160  
   161  func (p *PipeNode) String() string {
   162  	s := ""
   163  	if len(p.Decl) > 0 {
   164  		for i, v := range p.Decl {
   165  			if i > 0 {
   166  				s += ", "
   167  			}
   168  			s += v.String()
   169  		}
   170  		s += " := "
   171  	}
   172  	for i, c := range p.Cmds {
   173  		if i > 0 {
   174  			s += " | "
   175  		}
   176  		s += c.String()
   177  	}
   178  	return s
   179  }
   180  
   181  func (p *PipeNode) tree() *Tree {
   182  	return p.tr
   183  }
   184  
   185  func (p *PipeNode) CopyPipe() *PipeNode {
   186  	if p == nil {
   187  		return p
   188  	}
   189  	var decl []*VariableNode
   190  	for _, d := range p.Decl {
   191  		decl = append(decl, d.Copy().(*VariableNode))
   192  	}
   193  	n := p.tr.newPipeline(p.Pos, p.Line, decl)
   194  	for _, c := range p.Cmds {
   195  		n.append(c.Copy().(*CommandNode))
   196  	}
   197  	return n
   198  }
   199  
   200  func (p *PipeNode) Copy() Node {
   201  	return p.CopyPipe()
   202  }
   203  
   204  // ActionNode holds an action (something bounded by delimiters).
   205  // Control actions have their own nodes; ActionNode represents simple
   206  // ones such as field evaluations and parenthesized pipelines.
   207  type ActionNode struct {
   208  	NodeType
   209  	Pos
   210  	tr   *Tree
   211  	Line int       // The line number in the input. Deprecated: Kept for compatibility.
   212  	Pipe *PipeNode // The pipeline in the action.
   213  }
   214  
   215  func (t *Tree) newAction(pos Pos, line int, pipe *PipeNode) *ActionNode {
   216  	return &ActionNode{tr: t, NodeType: NodeAction, Pos: pos, Line: line, Pipe: pipe}
   217  }
   218  
   219  func (a *ActionNode) String() string {
   220  	return fmt.Sprintf("{{%s}}", a.Pipe)
   221  
   222  }
   223  
   224  func (a *ActionNode) tree() *Tree {
   225  	return a.tr
   226  }
   227  
   228  func (a *ActionNode) Copy() Node {
   229  	return a.tr.newAction(a.Pos, a.Line, a.Pipe.CopyPipe())
   230  
   231  }
   232  
   233  // CommandNode holds a command (a pipeline inside an evaluating action).
   234  type CommandNode struct {
   235  	NodeType
   236  	Pos
   237  	tr   *Tree
   238  	Args []Node // Arguments in lexical order: Identifier, field, or constant.
   239  }
   240  
   241  func (t *Tree) newCommand(pos Pos) *CommandNode {
   242  	return &CommandNode{tr: t, NodeType: NodeCommand, Pos: pos}
   243  }
   244  
   245  func (c *CommandNode) append(arg Node) {
   246  	c.Args = append(c.Args, arg)
   247  }
   248  
   249  func (c *CommandNode) String() string {
   250  	s := ""
   251  	for i, arg := range c.Args {
   252  		if i > 0 {
   253  			s += " "
   254  		}
   255  		if arg, ok := arg.(*PipeNode); ok {
   256  			s += "(" + arg.String() + ")"
   257  			continue
   258  		}
   259  		s += arg.String()
   260  	}
   261  	return s
   262  }
   263  
   264  func (c *CommandNode) tree() *Tree {
   265  	return c.tr
   266  }
   267  
   268  func (c *CommandNode) Copy() Node {
   269  	if c == nil {
   270  		return c
   271  	}
   272  	n := c.tr.newCommand(c.Pos)
   273  	for _, c := range c.Args {
   274  		n.append(c.Copy())
   275  	}
   276  	return n
   277  }
   278  
   279  // IdentifierNode holds an identifier.
   280  type IdentifierNode struct {
   281  	NodeType
   282  	Pos
   283  	tr    *Tree
   284  	Ident string // The identifier's name.
   285  }
   286  
   287  // NewIdentifier returns a new IdentifierNode with the given identifier name.
   288  func NewIdentifier(ident string) *IdentifierNode {
   289  	return &IdentifierNode{NodeType: NodeIdentifier, Ident: ident}
   290  }
   291  
   292  // SetPos sets the position. NewIdentifier is a public method so we can't modify its signature.
   293  // Chained for convenience.
   294  // TODO: fix one day?
   295  func (i *IdentifierNode) SetPos(pos Pos) *IdentifierNode {
   296  	i.Pos = pos
   297  	return i
   298  }
   299  
   300  // SetTree sets the parent tree for the node. NewIdentifier is a public method so we can't modify its signature.
   301  // Chained for convenience.
   302  // TODO: fix one day?
   303  func (i *IdentifierNode) SetTree(t *Tree) *IdentifierNode {
   304  	i.tr = t
   305  	return i
   306  }
   307  
   308  func (i *IdentifierNode) String() string {
   309  	return i.Ident
   310  }
   311  
   312  func (i *IdentifierNode) tree() *Tree {
   313  	return i.tr
   314  }
   315  
   316  func (i *IdentifierNode) Copy() Node {
   317  	return NewIdentifier(i.Ident).SetTree(i.tr).SetPos(i.Pos)
   318  }
   319  
   320  // VariableNode holds a list of variable names, possibly with chained field
   321  // accesses. The dollar sign is part of the (first) name.
   322  type VariableNode struct {
   323  	NodeType
   324  	Pos
   325  	tr    *Tree
   326  	Ident []string // Variable name and fields in lexical order.
   327  }
   328  
   329  func (t *Tree) newVariable(pos Pos, ident string) *VariableNode {
   330  	return &VariableNode{tr: t, NodeType: NodeVariable, Pos: pos, Ident: strings.Split(ident, ".")}
   331  }
   332  
   333  func (v *VariableNode) String() string {
   334  	s := ""
   335  	for i, id := range v.Ident {
   336  		if i > 0 {
   337  			s += "."
   338  		}
   339  		s += id
   340  	}
   341  	return s
   342  }
   343  
   344  func (v *VariableNode) tree() *Tree {
   345  	return v.tr
   346  }
   347  
   348  func (v *VariableNode) Copy() Node {
   349  	return &VariableNode{tr: v.tr, NodeType: NodeVariable, Pos: v.Pos, Ident: append([]string{}, v.Ident...)}
   350  }
   351  
   352  // DotNode holds the special identifier '.'.
   353  type DotNode struct {
   354  	NodeType
   355  	Pos
   356  	tr *Tree
   357  }
   358  
   359  func (t *Tree) newDot(pos Pos) *DotNode {
   360  	return &DotNode{tr: t, NodeType: NodeDot, Pos: pos}
   361  }
   362  
   363  func (d *DotNode) Type() NodeType {
   364  	// Override method on embedded NodeType for API compatibility.
   365  	// TODO: Not really a problem; could change API without effect but
   366  	// api tool complains.
   367  	return NodeDot
   368  }
   369  
   370  func (d *DotNode) String() string {
   371  	return "."
   372  }
   373  
   374  func (d *DotNode) tree() *Tree {
   375  	return d.tr
   376  }
   377  
   378  func (d *DotNode) Copy() Node {
   379  	return d.tr.newDot(d.Pos)
   380  }
   381  
   382  // NilNode holds the special identifier 'nil' representing an untyped nil constant.
   383  type NilNode struct {
   384  	NodeType
   385  	Pos
   386  	tr *Tree
   387  }
   388  
   389  func (t *Tree) newNil(pos Pos) *NilNode {
   390  	return &NilNode{tr: t, NodeType: NodeNil, Pos: pos}
   391  }
   392  
   393  func (n *NilNode) Type() NodeType {
   394  	// Override method on embedded NodeType for API compatibility.
   395  	// TODO: Not really a problem; could change API without effect but
   396  	// api tool complains.
   397  	return NodeNil
   398  }
   399  
   400  func (n *NilNode) String() string {
   401  	return "nil"
   402  }
   403  
   404  func (n *NilNode) tree() *Tree {
   405  	return n.tr
   406  }
   407  
   408  func (n *NilNode) Copy() Node {
   409  	return n.tr.newNil(n.Pos)
   410  }
   411  
   412  // FieldNode holds a field (identifier starting with '.').
   413  // The names may be chained ('.x.y').
   414  // The period is dropped from each ident.
   415  type FieldNode struct {
   416  	NodeType
   417  	Pos
   418  	tr    *Tree
   419  	Ident []string // The identifiers in lexical order.
   420  }
   421  
   422  func (t *Tree) newField(pos Pos, ident string) *FieldNode {
   423  	return &FieldNode{tr: t, NodeType: NodeField, Pos: pos, Ident: strings.Split(ident[1:], ".")} // [1:] to drop leading period
   424  }
   425  
   426  func (f *FieldNode) String() string {
   427  	s := ""
   428  	for _, id := range f.Ident {
   429  		s += "." + id
   430  	}
   431  	return s
   432  }
   433  
   434  func (f *FieldNode) tree() *Tree {
   435  	return f.tr
   436  }
   437  
   438  func (f *FieldNode) Copy() Node {
   439  	return &FieldNode{tr: f.tr, NodeType: NodeField, Pos: f.Pos, Ident: append([]string{}, f.Ident...)}
   440  }
   441  
   442  // ChainNode holds a term followed by a chain of field accesses (identifier starting with '.').
   443  // The names may be chained ('.x.y').
   444  // The periods are dropped from each ident.
   445  type ChainNode struct {
   446  	NodeType
   447  	Pos
   448  	tr    *Tree
   449  	Node  Node
   450  	Field []string // The identifiers in lexical order.
   451  }
   452  
   453  func (t *Tree) newChain(pos Pos, node Node) *ChainNode {
   454  	return &ChainNode{tr: t, NodeType: NodeChain, Pos: pos, Node: node}
   455  }
   456  
   457  // Add adds the named field (which should start with a period) to the end of the chain.
   458  func (c *ChainNode) Add(field string) {
   459  	if len(field) == 0 || field[0] != '.' {
   460  		panic("no dot in field")
   461  	}
   462  	field = field[1:] // Remove leading dot.
   463  	if field == "" {
   464  		panic("empty field")
   465  	}
   466  	c.Field = append(c.Field, field)
   467  }
   468  
   469  func (c *ChainNode) String() string {
   470  	s := c.Node.String()
   471  	if _, ok := c.Node.(*PipeNode); ok {
   472  		s = "(" + s + ")"
   473  	}
   474  	for _, field := range c.Field {
   475  		s += "." + field
   476  	}
   477  	return s
   478  }
   479  
   480  func (c *ChainNode) tree() *Tree {
   481  	return c.tr
   482  }
   483  
   484  func (c *ChainNode) Copy() Node {
   485  	return &ChainNode{tr: c.tr, NodeType: NodeChain, Pos: c.Pos, Node: c.Node, Field: append([]string{}, c.Field...)}
   486  }
   487  
   488  // BoolNode holds a boolean constant.
   489  type BoolNode struct {
   490  	NodeType
   491  	Pos
   492  	tr   *Tree
   493  	True bool // The value of the boolean constant.
   494  }
   495  
   496  func (t *Tree) newBool(pos Pos, true bool) *BoolNode {
   497  	return &BoolNode{tr: t, NodeType: NodeBool, Pos: pos, True: true}
   498  }
   499  
   500  func (b *BoolNode) String() string {
   501  	if b.True {
   502  		return "true"
   503  	}
   504  	return "false"
   505  }
   506  
   507  func (b *BoolNode) tree() *Tree {
   508  	return b.tr
   509  }
   510  
   511  func (b *BoolNode) Copy() Node {
   512  	return b.tr.newBool(b.Pos, b.True)
   513  }
   514  
   515  // NumberNode holds a number: signed or unsigned integer, float, or complex.
   516  // The value is parsed and stored under all the types that can represent the value.
   517  // This simulates in a small amount of code the behavior of Go's ideal constants.
   518  type NumberNode struct {
   519  	NodeType
   520  	Pos
   521  	tr         *Tree
   522  	IsInt      bool       // Number has an integral value.
   523  	IsUint     bool       // Number has an unsigned integral value.
   524  	IsFloat    bool       // Number has a floating-point value.
   525  	IsComplex  bool       // Number is complex.
   526  	Int64      int64      // The signed integer value.
   527  	Uint64     uint64     // The unsigned integer value.
   528  	Float64    float64    // The floating-point value.
   529  	Complex128 complex128 // The complex value.
   530  	Text       string     // The original textual representation from the input.
   531  }
   532  
   533  func (t *Tree) newNumber(pos Pos, text string, typ itemType) (*NumberNode, error) {
   534  	n := &NumberNode{tr: t, NodeType: NodeNumber, Pos: pos, Text: text}
   535  	switch typ {
   536  	case itemCharConstant:
   537  		rune, _, tail, err := strconv.UnquoteChar(text[1:], text[0])
   538  		if err != nil {
   539  			return nil, err
   540  		}
   541  		if tail != "'" {
   542  			return nil, fmt.Errorf("malformed character constant: %s", text)
   543  		}
   544  		n.Int64 = int64(rune)
   545  		n.IsInt = true
   546  		n.Uint64 = uint64(rune)
   547  		n.IsUint = true
   548  		n.Float64 = float64(rune) // odd but those are the rules.
   549  		n.IsFloat = true
   550  		return n, nil
   551  	case itemComplex:
   552  		// fmt.Sscan can parse the pair, so let it do the work.
   553  		if _, err := fmt.Sscan(text, &n.Complex128); err != nil {
   554  			return nil, err
   555  		}
   556  		n.IsComplex = true
   557  		n.simplifyComplex()
   558  		return n, nil
   559  	}
   560  	// Imaginary constants can only be complex unless they are zero.
   561  	if len(text) > 0 && text[len(text)-1] == 'i' {
   562  		f, err := strconv.ParseFloat(text[:len(text)-1], 64)
   563  		if err == nil {
   564  			n.IsComplex = true
   565  			n.Complex128 = complex(0, f)
   566  			n.simplifyComplex()
   567  			return n, nil
   568  		}
   569  	}
   570  	// Do integer test first so we get 0x123 etc.
   571  	u, err := strconv.ParseUint(text, 0, 64) // will fail for -0; fixed below.
   572  	if err == nil {
   573  		n.IsUint = true
   574  		n.Uint64 = u
   575  	}
   576  	i, err := strconv.ParseInt(text, 0, 64)
   577  	if err == nil {
   578  		n.IsInt = true
   579  		n.Int64 = i
   580  		if i == 0 {
   581  			n.IsUint = true // in case of -0.
   582  			n.Uint64 = u
   583  		}
   584  	}
   585  	// If an integer extraction succeeded, promote the float.
   586  	if n.IsInt {
   587  		n.IsFloat = true
   588  		n.Float64 = float64(n.Int64)
   589  	} else if n.IsUint {
   590  		n.IsFloat = true
   591  		n.Float64 = float64(n.Uint64)
   592  	} else {
   593  		f, err := strconv.ParseFloat(text, 64)
   594  		if err == nil {
   595  			// If we parsed it as a float but it looks like an integer,
   596  			// it's a huge number too large to fit in an int. Reject it.
   597  			if !strings.ContainsAny(text, ".eE") {
   598  				return nil, fmt.Errorf("integer overflow: %q", text)
   599  			}
   600  			n.IsFloat = true
   601  			n.Float64 = f
   602  			// If a floating-point extraction succeeded, extract the int if needed.
   603  			if !n.IsInt && float64(int64(f)) == f {
   604  				n.IsInt = true
   605  				n.Int64 = int64(f)
   606  			}
   607  			if !n.IsUint && float64(uint64(f)) == f {
   608  				n.IsUint = true
   609  				n.Uint64 = uint64(f)
   610  			}
   611  		}
   612  	}
   613  	if !n.IsInt && !n.IsUint && !n.IsFloat {
   614  		return nil, fmt.Errorf("illegal number syntax: %q", text)
   615  	}
   616  	return n, nil
   617  }
   618  
   619  // simplifyComplex pulls out any other types that are represented by the complex number.
   620  // These all require that the imaginary part be zero.
   621  func (n *NumberNode) simplifyComplex() {
   622  	n.IsFloat = imag(n.Complex128) == 0
   623  	if n.IsFloat {
   624  		n.Float64 = real(n.Complex128)
   625  		n.IsInt = float64(int64(n.Float64)) == n.Float64
   626  		if n.IsInt {
   627  			n.Int64 = int64(n.Float64)
   628  		}
   629  		n.IsUint = float64(uint64(n.Float64)) == n.Float64
   630  		if n.IsUint {
   631  			n.Uint64 = uint64(n.Float64)
   632  		}
   633  	}
   634  }
   635  
   636  func (n *NumberNode) String() string {
   637  	return n.Text
   638  }
   639  
   640  func (n *NumberNode) tree() *Tree {
   641  	return n.tr
   642  }
   643  
   644  func (n *NumberNode) Copy() Node {
   645  	nn := new(NumberNode)
   646  	*nn = *n // Easy, fast, correct.
   647  	return nn
   648  }
   649  
   650  // StringNode holds a string constant. The value has been "unquoted".
   651  type StringNode struct {
   652  	NodeType
   653  	Pos
   654  	tr     *Tree
   655  	Quoted string // The original text of the string, with quotes.
   656  	Text   string // The string, after quote processing.
   657  }
   658  
   659  func (t *Tree) newString(pos Pos, orig, text string) *StringNode {
   660  	return &StringNode{tr: t, NodeType: NodeString, Pos: pos, Quoted: orig, Text: text}
   661  }
   662  
   663  func (s *StringNode) String() string {
   664  	return s.Quoted
   665  }
   666  
   667  func (s *StringNode) tree() *Tree {
   668  	return s.tr
   669  }
   670  
   671  func (s *StringNode) Copy() Node {
   672  	return s.tr.newString(s.Pos, s.Quoted, s.Text)
   673  }
   674  
   675  // endNode represents an {{end}} action.
   676  // It does not appear in the final parse tree.
   677  type endNode struct {
   678  	NodeType
   679  	Pos
   680  	tr *Tree
   681  }
   682  
   683  func (t *Tree) newEnd(pos Pos) *endNode {
   684  	return &endNode{tr: t, NodeType: nodeEnd, Pos: pos}
   685  }
   686  
   687  func (e *endNode) String() string {
   688  	return "{{end}}"
   689  }
   690  
   691  func (e *endNode) tree() *Tree {
   692  	return e.tr
   693  }
   694  
   695  func (e *endNode) Copy() Node {
   696  	return e.tr.newEnd(e.Pos)
   697  }
   698  
   699  // elseNode represents an {{else}} action. Does not appear in the final tree.
   700  type elseNode struct {
   701  	NodeType
   702  	Pos
   703  	tr   *Tree
   704  	Line int // The line number in the input. Deprecated: Kept for compatibility.
   705  }
   706  
   707  func (t *Tree) newElse(pos Pos, line int) *elseNode {
   708  	return &elseNode{tr: t, NodeType: nodeElse, Pos: pos, Line: line}
   709  }
   710  
   711  func (e *elseNode) Type() NodeType {
   712  	return nodeElse
   713  }
   714  
   715  func (e *elseNode) String() string {
   716  	return "{{else}}"
   717  }
   718  
   719  func (e *elseNode) tree() *Tree {
   720  	return e.tr
   721  }
   722  
   723  func (e *elseNode) Copy() Node {
   724  	return e.tr.newElse(e.Pos, e.Line)
   725  }
   726  
   727  // BranchNode is the common representation of if, range, and with.
   728  type BranchNode struct {
   729  	NodeType
   730  	Pos
   731  	tr       *Tree
   732  	Line     int       // The line number in the input. Deprecated: Kept for compatibility.
   733  	Pipe     *PipeNode // The pipeline to be evaluated.
   734  	List     *ListNode // What to execute if the value is non-empty.
   735  	ElseList *ListNode // What to execute if the value is empty (nil if absent).
   736  }
   737  
   738  func (b *BranchNode) String() string {
   739  	name := ""
   740  	switch b.NodeType {
   741  	case NodeIf:
   742  		name = "if"
   743  	case NodeRange:
   744  		name = "range"
   745  	case NodeWith:
   746  		name = "with"
   747  	default:
   748  		panic("unknown branch type")
   749  	}
   750  	if b.ElseList != nil {
   751  		return fmt.Sprintf("{{%s %s}}%s{{else}}%s{{end}}", name, b.Pipe, b.List, b.ElseList)
   752  	}
   753  	return fmt.Sprintf("{{%s %s}}%s{{end}}", name, b.Pipe, b.List)
   754  }
   755  
   756  func (b *BranchNode) tree() *Tree {
   757  	return b.tr
   758  }
   759  
   760  func (b *BranchNode) Copy() Node {
   761  	switch b.NodeType {
   762  	case NodeIf:
   763  		return b.tr.newIf(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
   764  	case NodeRange:
   765  		return b.tr.newRange(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
   766  	case NodeWith:
   767  		return b.tr.newWith(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
   768  	default:
   769  		panic("unknown branch type")
   770  	}
   771  }
   772  
   773  // IfNode represents an {{if}} action and its commands.
   774  type IfNode struct {
   775  	BranchNode
   776  }
   777  
   778  func (t *Tree) newIf(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *IfNode {
   779  	return &IfNode{BranchNode{tr: t, NodeType: NodeIf, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
   780  }
   781  
   782  func (i *IfNode) Copy() Node {
   783  	return i.tr.newIf(i.Pos, i.Line, i.Pipe.CopyPipe(), i.List.CopyList(), i.ElseList.CopyList())
   784  }
   785  
   786  // RangeNode represents a {{range}} action and its commands.
   787  type RangeNode struct {
   788  	BranchNode
   789  }
   790  
   791  func (t *Tree) newRange(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *RangeNode {
   792  	return &RangeNode{BranchNode{tr: t, NodeType: NodeRange, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
   793  }
   794  
   795  func (r *RangeNode) Copy() Node {
   796  	return r.tr.newRange(r.Pos, r.Line, r.Pipe.CopyPipe(), r.List.CopyList(), r.ElseList.CopyList())
   797  }
   798  
   799  // WithNode represents a {{with}} action and its commands.
   800  type WithNode struct {
   801  	BranchNode
   802  }
   803  
   804  func (t *Tree) newWith(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *WithNode {
   805  	return &WithNode{BranchNode{tr: t, NodeType: NodeWith, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
   806  }
   807  
   808  func (w *WithNode) Copy() Node {
   809  	return w.tr.newWith(w.Pos, w.Line, w.Pipe.CopyPipe(), w.List.CopyList(), w.ElseList.CopyList())
   810  }
   811  
   812  // TemplateNode represents a {{template}} action.
   813  type TemplateNode struct {
   814  	NodeType
   815  	Pos
   816  	tr   *Tree
   817  	Line int       // The line number in the input. Deprecated: Kept for compatibility.
   818  	Name string    // The name of the template (unquoted).
   819  	Pipe *PipeNode // The command to evaluate as dot for the template.
   820  }
   821  
   822  func (t *Tree) newTemplate(pos Pos, line int, name string, pipe *PipeNode) *TemplateNode {
   823  	return &TemplateNode{tr: t, NodeType: NodeTemplate, Pos: pos, Line: line, Name: name, Pipe: pipe}
   824  }
   825  
   826  func (t *TemplateNode) String() string {
   827  	if t.Pipe == nil {
   828  		return fmt.Sprintf("{{template %q}}", t.Name)
   829  	}
   830  	return fmt.Sprintf("{{template %q %s}}", t.Name, t.Pipe)
   831  }
   832  
   833  func (t *TemplateNode) tree() *Tree {
   834  	return t.tr
   835  }
   836  
   837  func (t *TemplateNode) Copy() Node {
   838  	return t.tr.newTemplate(t.Pos, t.Line, t.Name, t.Pipe.CopyPipe())
   839  }
   840
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