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linkify.go
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linkify.go
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// Copyright 2013 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.
// This file implements LinkifyText which introduces
// links for identifiers pointing to their declarations.
// The approach does not cover all cases because godoc
// doesn't have complete type information, but it's
// reasonably good for browsing.
package godoc
import (
"fmt"
"go/ast"
"go/token"
"io"
"strconv"
)
// LinkifyText HTML-escapes source text and writes it to w.
// Identifiers that are in a "use" position (i.e., that are
// not being declared), are wrapped with HTML links pointing
// to the respective declaration, if possible. Comments are
// formatted the same way as with FormatText.
//
func LinkifyText(w io.Writer, text []byte, n ast.Node) {
links := linksFor(n)
i := 0 // links index
prev := "" // prev HTML tag
linkWriter := func(w io.Writer, _ int, start bool) {
// end tag
if !start {
if prev != "" {
fmt.Fprintf(w, `</%s>`, prev)
prev = ""
}
return
}
// start tag
prev = ""
if i < len(links) {
switch info := links[i]; {
case info.path != "" && info.name == "":
// package path
fmt.Fprintf(w, `<a href="/pkg/%s/">`, info.path)
prev = "a"
case info.path != "" && info.name != "":
// qualified identifier
fmt.Fprintf(w, `<a href="/pkg/%s/#%s">`, info.path, info.name)
prev = "a"
case info.path == "" && info.name != "":
// local identifier
if info.mode == identVal {
fmt.Fprintf(w, `<span id="%s">`, info.name)
prev = "span"
} else if ast.IsExported(info.name) {
fmt.Fprintf(w, `<a href="#%s">`, info.name)
prev = "a"
}
}
i++
}
}
idents := tokenSelection(text, token.IDENT)
comments := tokenSelection(text, token.COMMENT)
FormatSelections(w, text, linkWriter, idents, selectionTag, comments)
}
// A link describes the (HTML) link information for an identifier.
// The zero value of a link represents "no link".
//
type link struct {
mode identMode
path, name string // package path, identifier name
}
// linksFor returns the list of links for the identifiers used
// by node in the same order as they appear in the source.
//
func linksFor(node ast.Node) (list []link) {
modes := identModesFor(node)
// NOTE: We are expecting ast.Inspect to call the
// callback function in source text order.
ast.Inspect(node, func(node ast.Node) bool {
switch n := node.(type) {
case *ast.Ident:
m := modes[n]
info := link{mode: m}
switch m {
case identUse:
if n.Obj == nil && predeclared[n.Name] {
info.path = builtinPkgPath
}
info.name = n.Name
case identDef:
// any declaration expect const or var - empty link
case identVal:
// const or var declaration
info.name = n.Name
}
list = append(list, info)
return false
case *ast.SelectorExpr:
// Detect qualified identifiers of the form pkg.ident.
// If anything fails we return true and collect individual
// identifiers instead.
if x, _ := n.X.(*ast.Ident); x != nil {
// x must be a package for a qualified identifier
if obj := x.Obj; obj != nil && obj.Kind == ast.Pkg {
if spec, _ := obj.Decl.(*ast.ImportSpec); spec != nil {
// spec.Path.Value is the import path
if path, err := strconv.Unquote(spec.Path.Value); err == nil {
// Register two links, one for the package
// and one for the qualified identifier.
info := link{path: path}
list = append(list, info)
info.name = n.Sel.Name
list = append(list, info)
return false
}
}
}
}
}
return true
})
return
}
// The identMode describes how an identifier is "used" at its source location.
type identMode int
const (
identUse identMode = iota // identifier is used (must be zero value for identMode)
identDef // identifier is defined
identVal // identifier is defined in a const or var declaration
)
// identModesFor returns a map providing the identMode for each identifier used by node.
func identModesFor(node ast.Node) map[*ast.Ident]identMode {
m := make(map[*ast.Ident]identMode)
ast.Inspect(node, func(node ast.Node) bool {
switch n := node.(type) {
case *ast.Field:
for _, n := range n.Names {
m[n] = identDef
}
case *ast.ImportSpec:
if name := n.Name; name != nil {
m[name] = identDef
}
case *ast.ValueSpec:
for _, n := range n.Names {
m[n] = identVal
}
case *ast.TypeSpec:
m[n.Name] = identDef
case *ast.FuncDecl:
m[n.Name] = identDef
case *ast.AssignStmt:
// Short variable declarations only show up if we apply
// this code to all source code (as opposed to exported
// declarations only).
if n.Tok == token.DEFINE {
// Some of the lhs variables may be re-declared,
// so technically they are not defs. We don't
// care for now.
for _, x := range n.Lhs {
// Each lhs expression should be an
// ident, but we are conservative and check.
if n, _ := x.(*ast.Ident); n != nil {
m[n] = identVal
}
}
}
}
return true
})
return m
}
// The predeclared map represents the set of all predeclared identifiers.
// TODO(gri) This information is also encoded in similar maps in go/doc,
// but not exported. Consider exporting an accessor and using
// it instead.
var predeclared = map[string]bool{
"bool": true,
"byte": true,
"complex64": true,
"complex128": true,
"error": true,
"float32": true,
"float64": true,
"int": true,
"int8": true,
"int16": true,
"int32": true,
"int64": true,
"rune": true,
"string": true,
"uint": true,
"uint8": true,
"uint16": true,
"uint32": true,
"uint64": true,
"uintptr": true,
"true": true,
"false": true,
"iota": true,
"nil": true,
"append": true,
"cap": true,
"close": true,
"complex": true,
"copy": true,
"delete": true,
"imag": true,
"len": true,
"make": true,
"new": true,
"panic": true,
"print": true,
"println": true,
"real": true,
"recover": true,
}