present: record info in AST for reproducing present inputs

Commands like .code now have a TemplateCmd method
that returns the original command.

The Text struct now has a Raw field set when Pre==true.
It contains the original indented text, without the tab "fixing".

This helps building tooling that reformats or rewrites present files.

For golang/go#33955.

Change-Id: Ieb036e8b509a4531d120c597b19f2158306a5352
Reviewed-on: https://go-review.googlesource.com/c/tools/+/222845
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

present/caption.go

@@ -11,12 +11,14 @@ func init() {
 }
 
 type Caption struct {
+	Cmd  string // original command from present source
 	Text string
 }
 
+func (c Caption) PresentCmd() string   { return c.Cmd }
 func (c Caption) TemplateName() string { return "caption" }
 
 func parseCaption(_ *Context, _ string, _ int, text string) (Elem, error) {
 	text = strings.TrimSpace(strings.TrimPrefix(text, ".caption"))
-	return Caption{text}, nil
+	return Caption{text, text}, nil
 }

present/code.go

@@ -34,6 +34,7 @@ func init() {
 }
 
 type Code struct {
+	Cmd      string // original command from present source
 	Text     template.HTML
 	Play     bool   // runnable code
 	Edit     bool   // editable code
@@ -42,6 +43,7 @@ type Code struct {
 	Raw      []byte // content of the file
 }
 
+func (c Code) PresentCmd() string   { return c.Cmd }
 func (c Code) TemplateName() string { return "code" }
 
 // The input line is a .code or .play entry with a file name and an optional HLfoo marker on the end.
@@ -58,6 +60,7 @@ var (
 // The directive may also be ".play" if the snippet is executable.
 func parseCode(ctx *Context, sourceFile string, sourceLine int, cmd string) (Elem, error) {
 	cmd = strings.TrimSpace(cmd)
+	origCmd := cmd
 
 	// Pull off the HL, if any, from the end of the input line.
 	highlight := ""
@@ -129,6 +132,7 @@ func parseCode(ctx *Context, sourceFile string, sourceLine int, cmd string) (Ele
 		return nil, err
 	}
 	return Code{
+		Cmd:      origCmd,
 		Text:     template.HTML(buf.String()),
 		Play:     play,
 		Edit:     data.Edit,

present/html.go

@@ -21,11 +21,13 @@ func parseHTML(ctx *Context, fileName string, lineno int, text string) (Elem, er
 	if err != nil {
 		return nil, err
 	}
-	return HTML{template.HTML(b)}, nil
+	return HTML{text, template.HTML(b)}, nil
 }
 
 type HTML struct {
+	Cmd string // original command from present source
 	template.HTML
 }
 
+func (s HTML) PresentCmd() string   { return s.Cmd }
 func (s HTML) TemplateName() string { return "html" }

present/iframe.go

@@ -14,11 +14,13 @@ func init() {
 }
 
 type Iframe struct {
+	Cmd    string // original command from present source
 	URL    string
 	Width  int
 	Height int
 }
 
+func (i Iframe) PresentCmd() string   { return i.Cmd }
 func (i Iframe) TemplateName() string { return "iframe" }
 
 func parseIframe(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
@@ -26,7 +28,7 @@ func parseIframe(ctx *Context, fileName string, lineno int, text string) (Elem,
 	if len(args) < 2 {
 		return nil, fmt.Errorf("incorrect iframe invocation: %q", text)
 	}
-	i := Iframe{URL: args[1]}
+	i := Iframe{Cmd: text, URL: args[1]}
 	a, err := parseArgs(fileName, lineno, args[2:])
 	if err != nil {
 		return nil, err

present/image.go

@@ -14,11 +14,13 @@ func init() {
 }
 
 type Image struct {
+	Cmd    string // original command from present source
 	URL    string
 	Width  int
 	Height int
 }
 
+func (i Image) PresentCmd() string   { return i.Cmd }
 func (i Image) TemplateName() string { return "image" }
 
 func parseImage(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
@@ -26,7 +28,7 @@ func parseImage(ctx *Context, fileName string, lineno int, text string) (Elem, e
 	if len(args) < 2 {
 		return nil, fmt.Errorf("incorrect image invocation: %q", text)
 	}
-	img := Image{URL: args[1]}
+	img := Image{Cmd: text, URL: args[1]}
 	a, err := parseArgs(fileName, lineno, args[2:])
 	if err != nil {
 		return nil, err

present/link.go

@@ -16,10 +16,12 @@ func init() {
 }
 
 type Link struct {
+	Cmd   string // original command from present source
 	URL   *url.URL
 	Label string
 }
 
+func (l Link) PresentCmd() string   { return l.Cmd }
 func (l Link) TemplateName() string { return "link" }
 
 func parseLink(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
@@ -41,7 +43,7 @@ func parseLink(ctx *Context, fileName string, lineno int, text string) (Elem, er
 		}
 		label = strings.Replace(url.String(), scheme, "", 1)
 	}
-	return Link{url, label}, nil
+	return Link{text, url, label}, nil
 }
 
 func renderLink(href, text string) string {

present/parse.go

@@ -196,6 +196,7 @@ func execTemplate(t *template.Template, name string, data interface{}) (template
 type Text struct {
 	Lines []string
 	Pre   bool
+	Raw   string // original text, for Pre==true
 }
 
 func (t Text) TemplateName() string { return "text" }
@@ -371,9 +372,10 @@ func parseSections(ctx *Context, name string, lines *Lines, number []int) ([]Sec
 				}
 				lines.back()
 				pre := strings.Join(s, "\n")
+				raw := pre
 				pre = strings.Replace(pre, "\t", "    ", -1) // browsers treat tabs badly
 				pre = strings.TrimRightFunc(pre, unicode.IsSpace)
-				e = Text{Lines: []string{pre}, Pre: true}
+				e = Text{Lines: []string{pre}, Pre: true, Raw: raw}
 			case strings.HasPrefix(text, "- "):
 				var b []string
 				for {

present/video.go

@@ -14,12 +14,14 @@ func init() {
 }
 
 type Video struct {
+	Cmd        string // original command from present source
 	URL        string
 	SourceType string
 	Width      int
 	Height     int
 }
 
+func (v Video) PresentCmd() string   { return v.Cmd }
 func (v Video) TemplateName() string { return "video" }
 
 func parseVideo(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
@@ -27,7 +29,7 @@ func parseVideo(ctx *Context, fileName string, lineno int, text string) (Elem, e
 	if len(args) < 3 {
 		return nil, fmt.Errorf("incorrect video invocation: %q", text)
 	}
-	vid := Video{URL: args[1], SourceType: args[2]}
+	vid := Video{Cmd: text, URL: args[1], SourceType: args[2]}
 	a, err := parseArgs(fileName, lineno, args[3:])
 	if err != nil {
 		return nil, err