1 // Copyright 2015 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 // Package importer provides access to export data importers. 6 package importer 7 8 import ( 9 "go/build" 10 "go/internal/gccgoimporter" 11 "go/internal/gcimporter" 12 "go/internal/srcimporter" 13 "go/token" 14 "go/types" 15 "io" 16 "runtime" 17 ) 18 19 // A Lookup function returns a reader to access package data for 20 // a given import path, or an error if no matching package is found. 21 type Lookup func(path string) (io.ReadCloser, error) 22 23 // For returns an Importer for importing from installed packages 24 // for the compilers "gc" and "gccgo", or for importing directly 25 // from the source if the compiler argument is "source". In this 26 // latter case, importing may fail under circumstances where the 27 // exported API is not entirely defined in pure Go source code 28 // (if the package API depends on cgo-defined entities, the type 29 // checker won't have access to those). 30 // 31 // If lookup is nil, the default package lookup mechanism for the 32 // given compiler is used, and the resulting importer attempts 33 // to resolve relative and absolute import paths to canonical 34 // import path IDs before finding the imported file. 35 // 36 // If lookup is non-nil, then the returned importer calls lookup 37 // each time it needs to resolve an import path. In this mode 38 // the importer can only be invoked with canonical import paths 39 // (not relative or absolute ones); it is assumed that the translation 40 // to canonical import paths is being done by the client of the 41 // importer. 42 func For(compiler string, lookup Lookup) types.Importer { 43 switch compiler { 44 case "gc": 45 return &gcimports{ 46 packages: make(map[string]*types.Package), 47 lookup: lookup, 48 } 49 50 case "gccgo": 51 var inst gccgoimporter.GccgoInstallation 52 if err := inst.InitFromDriver("gccgo"); err != nil { 53 return nil 54 } 55 return &gccgoimports{ 56 packages: make(map[string]*types.Package), 57 importer: inst.GetImporter(nil, nil), 58 lookup: lookup, 59 } 60 61 case "source": 62 if lookup != nil { 63 panic("source importer for custom import path lookup not supported (issue #13847).") 64 } 65 66 return srcimporter.New(&build.Default, token.NewFileSet(), make(map[string]*types.Package)) 67 } 68 69 // compiler not supported 70 return nil 71 } 72 73 // Default returns an Importer for the compiler that built the running binary. 74 // If available, the result implements types.ImporterFrom. 75 func Default() types.Importer { 76 return For(runtime.Compiler, nil) 77 } 78 79 // gc importer 80 81 type gcimports struct { 82 packages map[string]*types.Package 83 lookup Lookup 84 } 85 86 func (m *gcimports) Import(path string) (*types.Package, error) { 87 return m.ImportFrom(path, "" /* no vendoring */, 0) 88 } 89 90 func (m *gcimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) { 91 if mode != 0 { 92 panic("mode must be 0") 93 } 94 return gcimporter.Import(m.packages, path, srcDir, m.lookup) 95 } 96 97 // gccgo importer 98 99 type gccgoimports struct { 100 packages map[string]*types.Package 101 importer gccgoimporter.Importer 102 lookup Lookup 103 } 104 105 func (m *gccgoimports) Import(path string) (*types.Package, error) { 106 return m.ImportFrom(path, "" /* no vendoring */, 0) 107 } 108 109 func (m *gccgoimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) { 110 if mode != 0 { 111 panic("mode must be 0") 112 } 113 return m.importer(m.packages, path, srcDir, m.lookup) 114 } 115
