golang importer 代码
文件路径：/src/go/importer/importer.go
/ Copyright 2015 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.
/ Package importer provides access to export data importers.
package importer
import (
"go/build"
"go/internal/gccgoimporter"
"go/internal/gcimporter"
"go/internal/srcimporter"
"go/token"
"go/types"
"io"
"runtime"
)
/ A Lookup function returns a reader to access package data for
/ a given import path, or an error if no matching package is found.
type Lookup func(path string) (io.ReadCloser, error)
/ ForCompiler returns an Importer for importing from installed packages
/ for the compilers "gc" and "gccgo", or for importing directly
/ from the source if the compiler argument is "source". In this
/ latter case, importing may fail under circumstances where the
/ exported API is not entirely defined in pure Go source code
/ (if the package API depends on cgo-defined entities, the type
/ checker won't have access to those).
/
/ The lookup function is called each time the resulting importer needs
/ to resolve an import path. In this mode the importer can only be
/ invoked with canonical import paths (not relative or absolute ones);
/ it is assumed that the translation to canonical import paths is being
/ done by the client of the importer.
/
/ A lookup function must be provided for correct module-aware operation.
/ Deprecated: If lookup is nil, for backwards-compatibility, the importer
/ will attempt to resolve imports in the $GOPATH workspace.
func ForCompiler(fset *token.FileSet, compiler string, lookup Lookup) types.Importer {
switch compiler {
case "gc":
return &gcimports{
fset: fset,
packages: make(map[string]*types.Package),
lookup: lookup,
}
case "gccgo":
var inst gccgoimporter.GccgoInstallation
if err := inst.InitFromDriver("gccgo"); err != nil {
return nil
}
return &gccgoimports{
packages: make(map[string]*types.Package),
importer: inst.GetImporter(nil, nil),
lookup: lookup,
}
case "source":
if lookup != nil {
panic("source importer for custom import path lookup not supported (issue #13847).")
}
return srcimporter.New(&build.Default, fset, make(map[string]*types.Package))
}
/ compiler not supported
return nil
}
/ For calls ForCompiler with a new FileSet.
/
/ Deprecated: Use ForCompiler, which populates a FileSet
/ with the positions of objects created by the importer.
func For(compiler string, lookup Lookup) types.Importer {
return ForCompiler(token.NewFileSet(), compiler, lookup)
}
/ Default returns an Importer for the compiler that built the running binary.
/ If available, the result implements types.ImporterFrom.
func Default() types.Importer {
return For(runtime.Compiler, nil)
}
/ gc importer
type gcimports struct {
fset *token.FileSet
packages map[string]*types.Package
lookup Lookup
}
func (m *gcimports) Import(path string) (*types.Package, error) {
return m.ImportFrom(path, "" /* no vendoring */, 0)
}
func (m *gcimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
if mode != 0 {
panic("mode must be 0")
}
return gcimporter.Import(m.fset, m.packages, path, srcDir, m.lookup)
}
/ gccgo importer
type gccgoimports struct {
packages map[string]*types.Package
importer gccgoimporter.Importer
lookup Lookup
}
func (m *gccgoimports) Import(path string) (*types.Package, error) {
return m.ImportFrom(path, "" /* no vendoring */, 0)
}
func (m *gccgoimports) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
if mode != 0 {
panic("mode must be 0")
}
return m.importer(m.packages, path, srcDir, m.lookup)
}