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         "path/filepath"
  17         "sync"
  18 )
  19
  20 // An Importer provides the context for importing packages from source code.
  21 type Importer struct {
  22         ctxt     *build.Context
  23         fset     *token.FileSet
  24         sizes    types.Sizes
  25         packages map[string]*types.Package
  26 }
  27
  28 // NewImporter returns a new Importer for the given context, file set, and map
  29 // of packages. The context is used to resolve import paths to package paths,
  30 // and identifying the files belonging to the package. If the context provides
  31 // non-nil file system functions, they are used instead of the regular package
  32 // os functions. The file set is used to track position information of package
  33 // files; and imported packages are added to the packages map.
  34 func New(ctxt *build.Context, fset *token.FileSet, packages map[string]*types.Package) *Importer {
  35         return &Importer{
  36                 ctxt:     ctxt,
  37                 fset:     fset,
  38                 sizes:    types.SizesFor(ctxt.Compiler, ctxt.GOARCH), // uses go/types default if GOARCH not found
  39                 packages: packages,
  40         }
  41 }
  42
  43 // Importing is a sentinel taking the place in Importer.packages
  44 // for a package that is in the process of being imported.
  45 var importing types.Package
  46
  47 // Import(path) is a shortcut for ImportFrom(path, ".", 0).
  48 func (p *Importer) Import(path string) (*types.Package, error) {
  49         return p.ImportFrom(path, ".", 0) // use "." rather than "" (see issue #24441)
  50 }
  51
  52 // ImportFrom imports the package with the given import path resolved from the given srcDir,
  53 // adds the new package to the set of packages maintained by the importer, and returns the
  54 // package. Package path resolution and file system operations are controlled by the context
  55 // maintained with the importer. The import mode must be zero but is otherwise ignored.
  56 // Packages that are not comprised entirely of pure Go files may fail to import because the
  57 // type checker may not be able to determine all exported entities (e.g. due to cgo dependencies).
  58 func (p *Importer) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
  59         if mode != 0 {
  60                 panic("non-zero import mode")
  61         }
  62
  63         if abs, err := p.absPath(srcDir); err == nil { // see issue #14282
  64                 srcDir = abs
  65         }
  66         bp, err := p.ctxt.Import(path, srcDir, 0)
  67         if err != nil {
  68                 return nil, err // err may be *build.NoGoError - return as is
  69         }
  70
  71         // package unsafe is known to the type checker
  72         if bp.ImportPath == "unsafe" {
  73                 return types.Unsafe, nil
  74         }
  75
  76         // no need to re-import if the package was imported completely before
  77         pkg := p.packages[bp.ImportPath]
  78         if pkg != nil {
  79                 if pkg == &importing {
  80                         return nil, fmt.Errorf("import cycle through package %q", bp.ImportPath)
  81                 }
  82                 if !pkg.Complete() {
  83                         // Package exists but is not complete - we cannot handle this
  84                         // at the moment since the source importer replaces the package
  85                         // wholesale rather than augmenting it (see #19337 for details).
  86                         // Return incomplete package with error (see #16088).
  87                         return pkg, fmt.Errorf("reimported partially imported package %q", bp.ImportPath)
  88                 }
  89                 return pkg, nil
  90         }
  91
  92         p.packages[bp.ImportPath] = &importing
  93         defer func() {
  94                 // clean up in case of error
  95                 // TODO(gri) Eventually we may want to leave a (possibly empty)
  96                 // package in the map in all cases (and use that package to
  97                 // identify cycles). See also issue 16088.
  98                 if p.packages[bp.ImportPath] == &importing {
  99                         p.packages[bp.ImportPath] = nil
 100                 }
 101         }()
 102
 103         var filenames []string
 104         filenames = append(filenames, bp.GoFiles...)
 105         filenames = append(filenames, bp.CgoFiles...)
 106
 107         files, err := p.parseFiles(bp.Dir, filenames)
 108         if err != nil {
 109                 return nil, err
 110         }
 111
 112         // type-check package files
 113         var firstHardErr error
 114         conf := types.Config{
 115                 IgnoreFuncBodies: true,
 116                 FakeImportC:      true,
 117                 // continue type-checking after the first error
 118                 Error: func(err error) {
 119                         if firstHardErr == nil && !err.(types.Error).Soft {
 120                                 firstHardErr = err
 121                         }
 122                 },
 123                 Importer: p,
 124                 Sizes:    p.sizes,
 125         }
 126         pkg, err = conf.Check(bp.ImportPath, p.fset, files, nil)
 127         if err != nil {
 128                 // If there was a hard error it is possibly unsafe
 129                 // to use the package as it may not be fully populated.
 130                 // Do not return it (see also #20837, #20855).
 131                 if firstHardErr != nil {
 132                         pkg = nil
 133                         err = firstHardErr // give preference to first hard error over any soft error
 134                 }
 135                 return pkg, fmt.Errorf("type-checking package %q failed (%v)", bp.ImportPath, err)
 136         }
 137         if firstHardErr != nil {
 138                 // this can only happen if we have a bug in go/types
 139                 panic("package is not safe yet no error was returned")
 140         }
 141
 142         p.packages[bp.ImportPath] = pkg
 143         return pkg, nil
 144 }
 145
 146 func (p *Importer) parseFiles(dir string, filenames []string) ([]*ast.File, error) {
 147         open := p.ctxt.OpenFile // possibly nil
 148
 149         files := make([]*ast.File, len(filenames))
 150         errors := make([]error, len(filenames))
 151
 152         var wg sync.WaitGroup
 153         wg.Add(len(filenames))
 154         for i, filename := range filenames {
 155                 go func(i int, filepath string) {
 156                         defer wg.Done()
 157                         if open != nil {
 158                                 src, err := open(filepath)
 159                                 if err != nil {
 160                                         errors[i] = fmt.Errorf("opening package file %s failed (%v)", filepath, err)
 161                                         return
 162                                 }
 163                                 files[i], errors[i] = parser.ParseFile(p.fset, filepath, src, 0)
 164                                 src.Close() // ignore Close error - parsing may have succeeded which is all we need
 165                         } else {
 166                                 // Special-case when ctxt doesn't provide a custom OpenFile and use the
 167                                 // parser's file reading mechanism directly. This appears to be quite a
 168                                 // bit faster than opening the file and providing an io.ReaderCloser in
 169                                 // both cases.
 170                                 // TODO(gri) investigate performance difference (issue #19281)
 171                                 files[i], errors[i] = parser.ParseFile(p.fset, filepath, nil, 0)
 172                         }
 173                 }(i, p.joinPath(dir, filename))
 174         }
 175         wg.Wait()
 176
 177         // if there are errors, return the first one for deterministic results
 178         for _, err := range errors {
 179                 if err != nil {
 180                         return nil, err
 181                 }
 182         }
 183
 184         return files, nil
 185 }
 186
 187 // context-controlled file system operations
 188
 189 func (p *Importer) absPath(path string) (string, error) {
 190         // TODO(gri) This should be using p.ctxt.AbsPath which doesn't
 191         // exist but probably should. See also issue #14282.
 192         return filepath.Abs(path)
 193 }
 194
 195 func (p *Importer) isAbsPath(path string) bool {
 196         if f := p.ctxt.IsAbsPath; f != nil {
 197                 return f(path)
 198         }
 199         return filepath.IsAbs(path)
 200 }
 201
 202 func (p *Importer) joinPath(elem ...string) string {
 203         if f := p.ctxt.JoinPath; f != nil {
 204                 return f(elem...)
 205         }
 206         return filepath.Join(elem...)
 207 }