text/template/parse: use human error prints

The previous version of all the node.String methods printed the parse
tree and was useful for developing the parse tree code. Now that that's done,
we might as well print the nodes using the standard template syntax.
It's much easier to read and makes error reporting look more natural.

Helps issue 2644.

R=rsc, n13m3y3r
CC=golang-dev
https://golang.org/cl/5553066

2 files changed, 77 insertions, 46 deletions

diff --git a/src/pkg/text/template/parse/node.go b/src/pkg/text/template/parse/node.go
index 4f43424239..0d030b8b4b 100644
--- a/src/pkg/text/template/parse/node.go
+++ b/src/pkg/text/template/parse/node.go
@@ -67,11 +67,9 @@ func (l *ListNode) append(n Node) {
 
 func (l *ListNode) String() string {
 	b := new(bytes.Buffer)
-	fmt.Fprint(b, "[")
 	for _, n := range l.Nodes {
 		fmt.Fprint(b, n)
 	}
-	fmt.Fprint(b, "]")
 	return b.String()
 }
 
@@ -86,7 +84,7 @@ func newText(text string) *TextNode {
 }
 
 func (t *TextNode) String() string {
-	return fmt.Sprintf("(text: %q)", t.Text)
+	return fmt.Sprintf("%q", t.Text)
 }
 
 // PipeNode holds a pipeline with optional declaration
@@ -106,10 +104,23 @@ func (p *PipeNode) append(command *CommandNode) {
 }
 
 func (p *PipeNode) String() string {
-	if p.Decl != nil {
-		return fmt.Sprintf("%v := %v", p.Decl, p.Cmds)
+	s := ""
+	if len(p.Decl) > 0 {
+		for i, v := range p.Decl {
+			if i > 0 {
+				s += ", "
+			}
+			s += v.String()
+		}
+		s += " := "
+	}
+	for i, c := range p.Cmds {
+		if i > 0 {
+			s += " | "
+		}
+		s += c.String()
 	}
-	return fmt.Sprintf("%v", p.Cmds)
+	return s
 }
 
 // ActionNode holds an action (something bounded by delimiters).
@@ -126,7 +137,8 @@ func newAction(line int, pipe *PipeNode) *ActionNode {
 }
 
 func (a *ActionNode) String() string {
-	return fmt.Sprintf("(action: %v)", a.Pipe)
+	return fmt.Sprintf("{{%s}}", a.Pipe)
+
 }
 
 // CommandNode holds a command (a pipeline inside an evaluating action).
@@ -144,7 +156,14 @@ func (c *CommandNode) append(arg Node) {
 }
 
 func (c *CommandNode) String() string {
-	return fmt.Sprintf("(command: %v)", c.Args)
+	s := ""
+	for i, arg := range c.Args {
+		if i > 0 {
+			s += " "
+		}
+		s += arg.String()
+	}
+	return s
 }
 
 // IdentifierNode holds an identifier.
@@ -159,7 +178,7 @@ func NewIdentifier(ident string) *IdentifierNode {
 }
 
 func (i *IdentifierNode) String() string {
-	return fmt.Sprintf("I=%s", i.Ident)
+	return i.Ident
 }
 
 // VariableNode holds a list of variable names. The dollar sign is
@@ -174,7 +193,14 @@ func newVariable(ident string) *VariableNode {
 }
 
 func (v *VariableNode) String() string {
-	return fmt.Sprintf("V=%s", v.Ident)
+	s := ""
+	for i, id := range v.Ident {
+		if i > 0 {
+			s += "."
+		}
+		s += id
+	}
+	return s
 }
 
 // DotNode holds the special identifier '.'. It is represented by a nil pointer.
@@ -189,7 +215,7 @@ func (d *DotNode) Type() NodeType {
 }
 
 func (d *DotNode) String() string {
-	return "{{<.>}}"
+	return "."
 }
 
 // FieldNode holds a field (identifier starting with '.').
@@ -205,7 +231,11 @@ func newField(ident string) *FieldNode {
 }
 
 func (f *FieldNode) String() string {
-	return fmt.Sprintf("F=%s", f.Ident)
+	s := ""
+	for _, id := range f.Ident {
+		s += "." + id
+	}
+	return s
 }
 
 // BoolNode holds a boolean constant.
@@ -219,7 +249,10 @@ func newBool(true bool) *BoolNode {
 }
 
 func (b *BoolNode) String() string {
-	return fmt.Sprintf("B=%t", b.True)
+	if b.True {
+		return "true"
+	}
+	return "false"
 }
 
 // NumberNode holds a number: signed or unsigned integer, float, or complex.
@@ -337,7 +370,7 @@ func (n *NumberNode) simplifyComplex() {
 }
 
 func (n *NumberNode) String() string {
-	return fmt.Sprintf("N=%s", n.Text)
+	return n.Text
 }
 
 // StringNode holds a string constant. The value has been "unquoted".
@@ -352,7 +385,7 @@ func newString(orig, text string) *StringNode {
 }
 
 func (s *StringNode) String() string {
-	return fmt.Sprintf("S=%#q", s.Text)
+	return s.Quoted
 }
 
 // endNode represents an {{end}} action. It is represented by a nil pointer.
@@ -411,9 +444,9 @@ func (b *BranchNode) String() string {
 		panic("unknown branch type")
 	}
 	if b.ElseList != nil {
-		return fmt.Sprintf("({{%s %s}} %s {{else}} %s)", name, b.Pipe, b.List, b.ElseList)
+		return fmt.Sprintf("{{%s %s}}%s{{else}}%s{{end}}", name, b.Pipe, b.List, b.ElseList)
 	}
-	return fmt.Sprintf("({{%s %s}} %s)", name, b.Pipe, b.List)
+	return fmt.Sprintf("{{%s %s}}%s{{end}}", name, b.Pipe, b.List)
 }
 
 // IfNode represents an {{if}} action and its commands.
diff --git a/src/pkg/text/template/parse/parse_test.go b/src/pkg/text/template/parse/parse_test.go
index b70c2143d3..13c5548abb 100644
--- a/src/pkg/text/template/parse/parse_test.go
+++ b/src/pkg/text/template/parse/parse_test.go
@@ -150,7 +150,7 @@ type parseTest struct {
 	name   string
 	input  string
 	ok     bool
-	result string
+	result string // what the user would see in an error message.
 }
 
 const (
@@ -160,59 +160,57 @@ const (
 
 var parseTests = []parseTest{
 	{"empty", "", noError,
-		`[]`},
+		``},
 	{"comment", "{{/*\n\n\n*/}}", noError,
-		`[]`},
+		``},
 	{"spaces", " \t\n", noError,
-		`[(text: " \t\n")]`},
+		`" \t\n"`},
 	{"text", "some text", noError,
-		`[(text: "some text")]`},
+		`"some text"`},
 	{"emptyAction", "{{}}", hasError,
-		`[(action: [])]`},
+		`{{}}`},
 	{"field", "{{.X}}", noError,
-		`[(action: [(command: [F=[X]])])]`},
+		`{{.X}}`},
 	{"simple command", "{{printf}}", noError,
-		`[(action: [(command: [I=printf])])]`},
+		`{{printf}}`},
 	{"$ invocation", "{{$}}", noError,
-		"[(action: [(command: [V=[$]])])]"},
+		"{{$}}"},
 	{"variable invocation", "{{with $x := 3}}{{$x 23}}{{end}}", noError,
-		"[({{with [V=[$x]] := [(command: [N=3])]}} [(action: [(command: [V=[$x] N=23])])])]"},
+		"{{with $x := 3}}{{$x 23}}{{end}}"},
 	{"variable with fields", "{{$.I}}", noError,
-		"[(action: [(command: [V=[$ I]])])]"},
+		"{{$.I}}"},
 	{"multi-word command", "{{printf `%d` 23}}", noError,
-		"[(action: [(command: [I=printf S=`%d` N=23])])]"},
+		"{{printf `%d` 23}}"},
 	{"pipeline", "{{.X|.Y}}", noError,
-		`[(action: [(command: [F=[X]]) (command: [F=[Y]])])]`},
+		`{{.X | .Y}}`},
 	{"pipeline with decl", "{{$x := .X|.Y}}", noError,
-		`[(action: [V=[$x]] := [(command: [F=[X]]) (command: [F=[Y]])])]`},
-	{"declaration", "{{.X|.Y}}", noError,
-		`[(action: [(command: [F=[X]]) (command: [F=[Y]])])]`},
+		`{{$x := .X | .Y}}`},
 	{"simple if", "{{if .X}}hello{{end}}", noError,
-		`[({{if [(command: [F=[X]])]}} [(text: "hello")])]`},
+		`{{if .X}}"hello"{{end}}`},
 	{"if with else", "{{if .X}}true{{else}}false{{end}}", noError,
-		`[({{if [(command: [F=[X]])]}} [(text: "true")] {{else}} [(text: "false")])]`},
+		`{{if .X}}"true"{{else}}"false"{{end}}`},
 	{"simple range", "{{range .X}}hello{{end}}", noError,
-		`[({{range [(command: [F=[X]])]}} [(text: "hello")])]`},
+		`{{range .X}}"hello"{{end}}`},
 	{"chained field range", "{{range .X.Y.Z}}hello{{end}}", noError,
-		`[({{range [(command: [F=[X Y Z]])]}} [(text: "hello")])]`},
+		`{{range .X.Y.Z}}"hello"{{end}}`},
 	{"nested range", "{{range .X}}hello{{range .Y}}goodbye{{end}}{{end}}", noError,
-		`[({{range [(command: [F=[X]])]}} [(text: "hello")({{range [(command: [F=[Y]])]}} [(text: "goodbye")])])]`},
+		`{{range .X}}"hello"{{range .Y}}"goodbye"{{end}}{{end}}`},
 	{"range with else", "{{range .X}}true{{else}}false{{end}}", noError,
-		`[({{range [(command: [F=[X]])]}} [(text: "true")] {{else}} [(text: "false")])]`},
+		`{{range .X}}"true"{{else}}"false"{{end}}`},
 	{"range over pipeline", "{{range .X|.M}}true{{else}}false{{end}}", noError,
-		`[({{range [(command: [F=[X]]) (command: [F=[M]])]}} [(text: "true")] {{else}} [(text: "false")])]`},
+		`{{range .X | .M}}"true"{{else}}"false"{{end}}`},
 	{"range []int", "{{range .SI}}{{.}}{{end}}", noError,
-		`[({{range [(command: [F=[SI]])]}} [(action: [(command: [{{<.>}}])])])]`},
+		`{{range .SI}}{{.}}{{end}}`},
 	{"constants", "{{range .SI 1 -3.2i true false 'a'}}{{end}}", noError,
-		`[({{range [(command: [F=[SI] N=1 N=-3.2i B=true B=false N='a'])]}} [])]`},
+		`{{range .SI 1 -3.2i true false 'a'}}{{end}}`},
 	{"template", "{{template `x`}}", noError,
-		`[{{template "x"}}]`},
+		`{{template "x"}}`},
 	{"template with arg", "{{template `x` .Y}}", noError,
-		`[{{template "x" [(command: [F=[Y]])]}}]`},
+		`{{template "x" .Y}}`},
 	{"with", "{{with .X}}hello{{end}}", noError,
-		`[({{with [(command: [F=[X]])]}} [(text: "hello")])]`},
+		`{{with .X}}"hello"{{end}}`},
 	{"with with else", "{{with .X}}hello{{else}}goodbye{{end}}", noError,
-		`[({{with [(command: [F=[X]])]}} [(text: "hello")] {{else}} [(text: "goodbye")])]`},
+		`{{with .X}}"hello"{{else}}"goodbye"{{end}}`},
 	// Errors.
 	{"unclosed action", "hello{{range", hasError, ""},
 	{"unmatched end", "{{end}}", hasError, ""},