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