1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
// Copyright 2016 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.
//go:build go1.7 && gc && !android && !ios && (unix || aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || plan9 || windows)
// +build go1.7
// +build gc
// +build !android
// +build !ios
// +build unix aix darwin dragonfly freebsd linux netbsd openbsd solaris plan9 windows
package gcexportdata_test
import (
"fmt"
"go/ast"
"go/parser"
"go/token"
"go/types"
"log"
"os"
"path/filepath"
"strings"
"golang.org/x/tools/go/gcexportdata"
)
// ExampleRead uses gcexportdata.Read to load type information for the
// "fmt" package from the fmt.a file produced by the gc compiler.
func ExampleRead() {
// Find the export data file.
filename, path := gcexportdata.Find("fmt", "")
if filename == "" {
log.Fatalf("can't find export data for fmt")
}
fmt.Printf("Package path: %s\n", path)
// Open and read the file.
f, err := os.Open(filename)
if err != nil {
log.Fatal(err)
}
defer f.Close()
r, err := gcexportdata.NewReader(f)
if err != nil {
log.Fatalf("reading export data %s: %v", filename, err)
}
// Decode the export data.
fset := token.NewFileSet()
imports := make(map[string]*types.Package)
pkg, err := gcexportdata.Read(r, fset, imports, path)
if err != nil {
log.Fatal(err)
}
// We can see all the names in Names.
members := pkg.Scope().Names()
foundPrintln := false
for _, member := range members {
if member == "Println" {
foundPrintln = true
break
}
}
fmt.Print("Package members: ")
if foundPrintln {
fmt.Println("Println found")
} else {
fmt.Println("Println not found")
}
// We can also look up a name directly using Lookup.
println := pkg.Scope().Lookup("Println")
// go 1.18+ uses the 'any' alias
typ := strings.ReplaceAll(println.Type().String(), "interface{}", "any")
fmt.Printf("Println type: %s\n", typ)
posn := fset.Position(println.Pos())
// make example deterministic
posn.Line = 123
fmt.Printf("Println location: %s\n", slashify(posn))
// Output:
//
// Package path: fmt
// Package members: Println found
// Println type: func(a ...any) (n int, err error)
// Println location: $GOROOT/src/fmt/print.go:123:1
}
// ExampleNewImporter demonstrates usage of NewImporter to provide type
// information for dependencies when type-checking Go source code.
func ExampleNewImporter() {
const src = `package myrpc
// choosing a package that doesn't change across releases
import "net/rpc"
const serverError rpc.ServerError = ""
`
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "myrpc.go", src, 0)
if err != nil {
log.Fatal(err)
}
packages := make(map[string]*types.Package)
imp := gcexportdata.NewImporter(fset, packages)
conf := types.Config{Importer: imp}
pkg, err := conf.Check("myrpc", fset, []*ast.File{f}, nil)
if err != nil {
log.Fatal(err)
}
// object from imported package
pi := packages["net/rpc"].Scope().Lookup("ServerError")
fmt.Printf("type %s.%s %s // %s\n",
pi.Pkg().Path(),
pi.Name(),
pi.Type().Underlying(),
slashify(fset.Position(pi.Pos())),
)
// object in source package
twopi := pkg.Scope().Lookup("serverError")
fmt.Printf("const %s %s = %s // %s\n",
twopi.Name(),
twopi.Type(),
twopi.(*types.Const).Val(),
slashify(fset.Position(twopi.Pos())),
)
// Output:
//
// type net/rpc.ServerError string // $GOROOT/src/net/rpc/client.go:20:1
// const serverError net/rpc.ServerError = "" // myrpc.go:6:7
}
func slashify(posn token.Position) token.Position {
posn.Filename = filepath.ToSlash(posn.Filename) // for MS Windows portability
return posn
}
|
