libgo/go/go/internal/srcimporter/srcimporter.go

   1 // Copyright 2017 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 srcimporter implements importing directly
   6 // from source files rather than installed packages.
   7 package srcimporter // import "go/internal/srcimporter"
   8
   9 import (
  10         "fmt"
  11         "go/ast"
  12         "go/build"
  13         "go/parser"
  14         "go/token"
  15         "go/types"
  16         "io"
  17         "os"
  18         "path/filepath"
  19         "sync"
  20 )
  21
  22 // An Importer provides the context for importing packages from source code.
  23 type Importer struct {
  24         ctxt     *build.Context
  25         fset     *token.FileSet
  26         sizes    types.Sizes
  27         packages map[string]*types.Package
  28 }
  29
  30 // NewImporter returns a new Importer for the given context, file set, and map
  31 // of packages. The context is used to resolve import paths to package paths,
  32 // and identifying the files belonging to the package. If the context provides
  33 // non-nil file system functions, they are used instead of the regular package
  34 // os functions. The file set is used to track position information of package
  35 // files; and imported packages are added to the packages map.
  36 func New(ctxt *build.Context, fset *token.FileSet, packages map[string]*types.Package) *Importer {
  37         return &Importer{
  38                 ctxt:     ctxt,
  39                 fset:     fset,
  40                 sizes:    types.SizesFor(ctxt.Compiler, ctxt.GOARCH), // uses go/types default if GOARCH not found
  41                 packages: packages,
  42         }
  43 }
  44
  45 // Importing is a sentinel taking the place in Importer.packages
  46 // for a package that is in the process of being imported.
  47 var importing types.Package
  48
  49 // Import(path) is a shortcut for ImportFrom(path, ".", 0).
  50 func (p *Importer) Import(path string) (*types.Package, error) {
  51         return p.ImportFrom(path, ".", 0) // use "." rather than "" (see issue #24441)
  52 }
  53
  54 // ImportFrom imports the package with the given import path resolved from the given srcDir,
  55 // adds the new package to the set of packages maintained by the importer, and returns the
  56 // package. Package path resolution and file system operations are controlled by the context
  57 // maintained with the importer. The import mode must be zero but is otherwise ignored.
  58 // Packages that are not comprised entirely of pure Go files may fail to import because the
  59 // type checker may not be able to determine all exported entities (e.g. due to cgo dependencies).
  60 func (p *Importer) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
  61         if mode != 0 {
  62                 panic("non-zero import mode")
  63         }
  64
  65         if abs, err := p.absPath(srcDir); err == nil { // see issue #14282
  66                 srcDir = abs
  67         }
  68         bp, err := p.ctxt.Import(path, srcDir, 0)
  69         if err != nil {
  70                 return nil, err // err may be *build.NoGoError - return as is
  71         }
  72
  73         // package unsafe is known to the type checker
  74         if bp.ImportPath == "unsafe" {
  75                 return types.Unsafe, nil
  76         }
  77
  78         // no need to re-import if the package was imported completely before
  79         pkg := p.packages[bp.ImportPath]
  80         if pkg != nil {
  81                 if pkg == &importing {
  82                         return nil, fmt.Errorf("import cycle through package %q", bp.ImportPath)
  83                 }
  84                 if !pkg.Complete() {
  85                         // Package exists but is not complete - we cannot handle this
  86                         // at the moment since the source importer replaces the package
  87                         // wholesale rather than augmenting it (see #19337 for details).
  88                         // Return incomplete package with error (see #16088).
  89                         return pkg, fmt.Errorf("reimported partially imported package %q", bp.ImportPath)
  90                 }
  91                 return pkg, nil
  92         }
  93
  94         p.packages[bp.ImportPath] = &importing
  95         defer func() {
  96                 // clean up in case of error
  97                 // TODO(gri) Eventually we may want to leave a (possibly empty)
  98                 // package in the map in all cases (and use that package to
  99                 // identify cycles). See also issue 16088.
 100                 if p.packages[bp.ImportPath] == &importing {
 101                         p.packages[bp.ImportPath] = nil
 102                 }
 103         }()
 104
 105         var filenames []string
 106         filenames = append(filenames, bp.GoFiles...)
 107         filenames = append(filenames, bp.CgoFiles...)
 108
 109         files, err := p.parseFiles(bp.Dir, filenames)
 110         if err != nil {
 111                 return nil, err
 112         }
 113
 114         // type-check package files
 115         var firstHardErr error
 116         conf := types.Config{
 117                 IgnoreFuncBodies: true,
 118                 FakeImportC:      true,
 119                 // continue type-checking after the first error
 120                 Error: func(err error) {
 121                         if firstHardErr == nil && !err.(types.Error).Soft {
 122                                 firstHardErr = err
 123                         }
 124                 },
 125                 Importer: p,
 126                 Sizes:    p.sizes,
 127         }
 128         pkg, err = conf.Check(bp.ImportPath, p.fset, files, nil)
 129         if err != nil {
 130                 // If there was a hard error it is possibly unsafe
 131                 // to use the package as it may not be fully populated.
 132                 // Do not return it (see also #20837, #20855).
 133                 if firstHardErr != nil {
 134                         pkg = nil
 135                         err = firstHardErr // give preference to first hard error over any soft error
 136                 }
 137                 return pkg, fmt.Errorf("type-checking package %q failed (%v)", bp.ImportPath, err)
 138         }
 139         if firstHardErr != nil {
 140                 // this can only happen if we have a bug in go/types
 141                 panic("package is not safe yet no error was returned")
 142         }
 143
 144         p.packages[bp.ImportPath] = pkg
 145         return pkg, nil
 146 }
 147
 148 func (p *Importer) parseFiles(dir string, filenames []string) ([]*ast.File, error) {
 149         // use build.Context's OpenFile if there is one
 150         open := p.ctxt.OpenFile
 151         if open == nil {
 152                 open = func(name string) (io.ReadCloser, error) { return os.Open(name) }
 153         }
 154
 155         files := make([]*ast.File, len(filenames))
 156         errors := make([]error, len(filenames))
 157
 158         var wg sync.WaitGroup
 159         wg.Add(len(filenames))
 160         for i, filename := range filenames {
 161                 go func(i int, filepath string) {
 162                         defer wg.Done()
 163                         src, err := open(filepath)
 164                         if err != nil {
 165                                 errors[i] = err // open provides operation and filename in error
 166                                 return
 167                         }
 168                         files[i], errors[i] = parser.ParseFile(p.fset, filepath, src, 0)
 169                         src.Close() // ignore Close error - parsing may have succeeded which is all we need
 170                 }(i, p.joinPath(dir, filename))
 171         }
 172         wg.Wait()
 173
 174         // if there are errors, return the first one for deterministic results
 175         for _, err := range errors {
 176                 if err != nil {
 177                         return nil, err
 178                 }
 179         }
 180
 181         return files, nil
 182 }
 183
 184 // context-controlled file system operations
 185
 186 func (p *Importer) absPath(path string) (string, error) {
 187         // TODO(gri) This should be using p.ctxt.AbsPath which doesn't
 188         // exist but probably should. See also issue #14282.
 189         return filepath.Abs(path)
 190 }
 191
 192 func (p *Importer) isAbsPath(path string) bool {
 193         if f := p.ctxt.IsAbsPath; f != nil {
 194                 return f(path)
 195         }
 196         return filepath.IsAbs(path)
 197 }
 198
 199 func (p *Importer) joinPath(elem ...string) string {
 200         if f := p.ctxt.JoinPath; f != nil {
 201                 return f(elem...)
 202         }
 203         return filepath.Join(elem...)
 204 }