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.
6package importer
7
8import (
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.
21type Lookup func(path string) (io.ReadCloser, error)
22
23// ForCompiler 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// The lookup function is called each time the resulting importer needs
32// to resolve an import path. In this mode the importer can only be
33// invoked with canonical import paths (not relative or absolute ones);
34// it is assumed that the translation to canonical import paths is being
35// done by the client of the importer.
36//
37// A lookup function must be provided for correct module-aware operation.
38// Deprecated: If lookup is nil, for backwards-compatibility, the importer
39// will attempt to resolve imports in the $GOPATH workspace.
40func ForCompiler(fset *token.FileSet, compiler string, lookup Lookup) types.Importer {
41	switch compiler {
42	case "gc":
43		return &gcimports{
44			fset:     fset,
45			packages: make(map[string]*types.Package),
46			lookup:   lookup,
47		}
48
49	case "gccgo":
50		var inst gccgoimporter.GccgoInstallation
51		if err := inst.InitFromDriver("gccgo"); err != nil {
52			return nil
53		}
54		return &gccgoimports{
55			packages: make(map[string]*types.Package),
56			importer: inst.GetImporter(nil, nil),
57			lookup:   lookup,
58		}
59
60	case "source":
61		if lookup != nil {
62			panic("source importer for custom import path lookup not supported (issue #13847).")
63		}
64
65		return srcimporter.New(&build.Default, fset, make(map[string]*types.Package))
66	}
67
68	// compiler not supported
69	return nil
70}
71
72// For calls [ForCompiler] with a new FileSet.
73//
74// Deprecated: Use [ForCompiler], which populates a FileSet
75// with the positions of objects created by the importer.
76func For(compiler string, lookup Lookup) types.Importer {
77	return ForCompiler(token.NewFileSet(), compiler, lookup)
78}
79
80// Default returns an Importer for the compiler that built the running binary.
81// If available, the result implements [types.ImporterFrom].
82func Default() types.Importer {
83	return For(runtime.Compiler, nil)
84}
85
86// gc importer
87
88type gcimports struct {
89	fset     *token.FileSet
90	packages map[string]*types.Package
91	lookup   Lookup
92}
93
94func (m *gcimports) Import(path string) (*types.Package, error) {
95	return m.ImportFrom(path, "" /* no vendoring */, 0)
96}
97
98func (m *gcimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
99	if mode != 0 {
100		panic("mode must be 0")
101	}
102	return gcimporter.Import(m.fset, m.packages, path, srcDir, m.lookup)
103}
104
105// gccgo importer
106
107type gccgoimports struct {
108	packages map[string]*types.Package
109	importer gccgoimporter.Importer
110	lookup   Lookup
111}
112
113func (m *gccgoimports) Import(path string) (*types.Package, error) {
114	return m.ImportFrom(path, "" /* no vendoring */, 0)
115}
116
117func (m *gccgoimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
118	if mode != 0 {
119		panic("mode must be 0")
120	}
121	return m.importer(m.packages, path, srcDir, m.lookup)
122}
123