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// Copyright 2009 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 contains the infrastructure to create a code
// snippet for search results.
//
// Note: At the moment, this only creates HTML snippets.
package main
import (
"bytes"
"go/ast"
"go/token"
"fmt"
)
type Snippet struct {
Line int
Text []byte
}
func newSnippet(fset *token.FileSet, decl ast.Decl, id *ast.Ident) *Snippet {
// TODO instead of pretty-printing the node, should use the original source instead
var buf bytes.Buffer
writeNode(&buf, fset, decl, true)
return &Snippet{fset.Position(id.Pos()).Line, FormatText(buf.Bytes(), -1, true, id.Name, nil)}
}
func findSpec(list []ast.Spec, id *ast.Ident) ast.Spec {
for _, spec := range list {
switch s := spec.(type) {
case *ast.ImportSpec:
if s.Name == id {
return s
}
case *ast.ValueSpec:
for _, n := range s.Names {
if n == id {
return s
}
}
case *ast.TypeSpec:
if s.Name == id {
return s
}
}
}
return nil
}
func genSnippet(fset *token.FileSet, d *ast.GenDecl, id *ast.Ident) *Snippet {
s := findSpec(d.Specs, id)
if s == nil {
return nil // declaration doesn't contain id - exit gracefully
}
// only use the spec containing the id for the snippet
dd := &ast.GenDecl{d.Doc, d.Pos(), d.Tok, d.Lparen, []ast.Spec{s}, d.Rparen}
return newSnippet(fset, dd, id)
}
func funcSnippet(fset *token.FileSet, d *ast.FuncDecl, id *ast.Ident) *Snippet {
if d.Name != id {
return nil // declaration doesn't contain id - exit gracefully
}
// only use the function signature for the snippet
dd := &ast.FuncDecl{d.Doc, d.Recv, d.Name, d.Type, nil}
return newSnippet(fset, dd, id)
}
// NewSnippet creates a text snippet from a declaration decl containing an
// identifier id. Parts of the declaration not containing the identifier
// may be removed for a more compact snippet.
//
func NewSnippet(fset *token.FileSet, decl ast.Decl, id *ast.Ident) (s *Snippet) {
switch d := decl.(type) {
case *ast.GenDecl:
s = genSnippet(fset, d, id)
case *ast.FuncDecl:
s = funcSnippet(fset, d, id)
}
// handle failure gracefully
if s == nil {
var buf bytes.Buffer
fmt.Fprintf(&buf, `<span class="alert">could not generate a snippet for <span class="highlight">%s</span></span>`, id.Name)
s = &Snippet{
fset.Position(id.Pos()).Line,
buf.Bytes(),
}
}
return
}
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