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  	exec "internal/execabs"
    17  	"io"
    18  	"os"
    19  	"path/filepath"
    20  	"strings"
    21  	"sync"
    22  	_ "unsafe" // for go:linkname
    23  )
    24  
    25  // An Importer provides the context for importing packages from source code.
    26  type Importer struct {
    27  	ctxt     *build.Context
    28  	fset     *token.FileSet
    29  	sizes    types.Sizes
    30  	packages map[string]*types.Package
    31  }
    32  
    33  // New returns a new Importer for the given context, file set, and map
    34  // of packages. The context is used to resolve import paths to package paths,
    35  // and identifying the files belonging to the package. If the context provides
    36  // non-nil file system functions, they are used instead of the regular package
    37  // os functions. The file set is used to track position information of package
    38  // files; and imported packages are added to the packages map.
    39  func New(ctxt *build.Context, fset *token.FileSet, packages map[string]*types.Package) *Importer {
    40  	return &Importer{
    41  		ctxt:     ctxt,
    42  		fset:     fset,
    43  		sizes:    types.SizesFor(ctxt.Compiler, ctxt.GOARCH), // uses go/types default if GOARCH not found
    44  		packages: packages,
    45  	}
    46  }
    47  
    48  // Importing is a sentinel taking the place in Importer.packages
    49  // for a package that is in the process of being imported.
    50  var importing types.Package
    51  
    52  // Import(path) is a shortcut for ImportFrom(path, ".", 0).
    53  func (p *Importer) Import(path string) (*types.Package, error) {
    54  	return p.ImportFrom(path, ".", 0) // use "." rather than "" (see issue #24441)
    55  }
    56  
    57  // ImportFrom imports the package with the given import path resolved from the given srcDir,
    58  // adds the new package to the set of packages maintained by the importer, and returns the
    59  // package. Package path resolution and file system operations are controlled by the context
    60  // maintained with the importer. The import mode must be zero but is otherwise ignored.
    61  // Packages that are not comprised entirely of pure Go files may fail to import because the
    62  // type checker may not be able to determine all exported entities (e.g. due to cgo dependencies).
    63  func (p *Importer) ImportFrom(path, srcDir string, mode types.ImportMode) (*types.Package, error) {
    64  	if mode != 0 {
    65  		panic("non-zero import mode")
    66  	}
    67  
    68  	if abs, err := p.absPath(srcDir); err == nil { // see issue #14282
    69  		srcDir = abs
    70  	}
    71  	bp, err := p.ctxt.Import(path, srcDir, 0)
    72  	if err != nil {
    73  		return nil, err // err may be *build.NoGoError - return as is
    74  	}
    75  
    76  	// package unsafe is known to the type checker
    77  	if bp.ImportPath == "unsafe" {
    78  		return types.Unsafe, nil
    79  	}
    80  
    81  	// no need to re-import if the package was imported completely before
    82  	pkg := p.packages[bp.ImportPath]
    83  	if pkg != nil {
    84  		if pkg == &importing {
    85  			return nil, fmt.Errorf("import cycle through package %q", bp.ImportPath)
    86  		}
    87  		if !pkg.Complete() {
    88  			// Package exists but is not complete - we cannot handle this
    89  			// at the moment since the source importer replaces the package
    90  			// wholesale rather than augmenting it (see #19337 for details).
    91  			// Return incomplete package with error (see #16088).
    92  			return pkg, fmt.Errorf("reimported partially imported package %q", bp.ImportPath)
    93  		}
    94  		return pkg, nil
    95  	}
    96  
    97  	p.packages[bp.ImportPath] = &importing
    98  	defer func() {
    99  		// clean up in case of error
   100  		// TODO(gri) Eventually we may want to leave a (possibly empty)
   101  		// package in the map in all cases (and use that package to
   102  		// identify cycles). See also issue 16088.
   103  		if p.packages[bp.ImportPath] == &importing {
   104  			p.packages[bp.ImportPath] = nil
   105  		}
   106  	}()
   107  
   108  	var filenames []string
   109  	filenames = append(filenames, bp.GoFiles...)
   110  	filenames = append(filenames, bp.CgoFiles...)
   111  
   112  	files, err := p.parseFiles(bp.Dir, filenames)
   113  	if err != nil {
   114  		return nil, err
   115  	}
   116  
   117  	// type-check package files
   118  	var firstHardErr error
   119  	conf := types.Config{
   120  		IgnoreFuncBodies: true,
   121  		// continue type-checking after the first error
   122  		Error: func(err error) {
   123  			if firstHardErr == nil && !err.(types.Error).Soft {
   124  				firstHardErr = err
   125  			}
   126  		},
   127  		Importer: p,
   128  		Sizes:    p.sizes,
   129  	}
   130  	if len(bp.CgoFiles) > 0 {
   131  		if p.ctxt.OpenFile != nil {
   132  			// cgo, gcc, pkg-config, etc. do not support
   133  			// build.Context's VFS.
   134  			conf.FakeImportC = true
   135  		} else {
   136  			setUsesCgo(&conf)
   137  			file, err := p.cgo(bp)
   138  			if err != nil {
   139  				return nil, err
   140  			}
   141  			files = append(files, file)
   142  		}
   143  	}
   144  
   145  	pkg, err = conf.Check(bp.ImportPath, p.fset, files, nil)
   146  	if err != nil {
   147  		// If there was a hard error it is possibly unsafe
   148  		// to use the package as it may not be fully populated.
   149  		// Do not return it (see also #20837, #20855).
   150  		if firstHardErr != nil {
   151  			pkg = nil
   152  			err = firstHardErr // give preference to first hard error over any soft error
   153  		}
   154  		return pkg, fmt.Errorf("type-checking package %q failed (%v)", bp.ImportPath, err)
   155  	}
   156  	if firstHardErr != nil {
   157  		// this can only happen if we have a bug in go/types
   158  		panic("package is not safe yet no error was returned")
   159  	}
   160  
   161  	p.packages[bp.ImportPath] = pkg
   162  	return pkg, nil
   163  }
   164  
   165  func (p *Importer) parseFiles(dir string, filenames []string) ([]*ast.File, error) {
   166  	// use build.Context's OpenFile if there is one
   167  	open := p.ctxt.OpenFile
   168  	if open == nil {
   169  		open = func(name string) (io.ReadCloser, error) { return os.Open(name) }
   170  	}
   171  
   172  	files := make([]*ast.File, len(filenames))
   173  	errors := make([]error, len(filenames))
   174  
   175  	var wg sync.WaitGroup
   176  	wg.Add(len(filenames))
   177  	for i, filename := range filenames {
   178  		go func(i int, filepath string) {
   179  			defer wg.Done()
   180  			src, err := open(filepath)
   181  			if err != nil {
   182  				errors[i] = err // open provides operation and filename in error
   183  				return
   184  			}
   185  			files[i], errors[i] = parser.ParseFile(p.fset, filepath, src, 0)
   186  			src.Close() // ignore Close error - parsing may have succeeded which is all we need
   187  		}(i, p.joinPath(dir, filename))
   188  	}
   189  	wg.Wait()
   190  
   191  	// if there are errors, return the first one for deterministic results
   192  	for _, err := range errors {
   193  		if err != nil {
   194  			return nil, err
   195  		}
   196  	}
   197  
   198  	return files, nil
   199  }
   200  
   201  func (p *Importer) cgo(bp *build.Package) (*ast.File, error) {
   202  	tmpdir, err := os.MkdirTemp("", "srcimporter")
   203  	if err != nil {
   204  		return nil, err
   205  	}
   206  	defer os.RemoveAll(tmpdir)
   207  
   208  	args := []string{"go", "tool", "cgo", "-objdir", tmpdir}
   209  	if bp.Goroot {
   210  		switch bp.ImportPath {
   211  		case "runtime/cgo":
   212  			args = append(args, "-import_runtime_cgo=false", "-import_syscall=false")
   213  		case "runtime/race":
   214  			args = append(args, "-import_syscall=false")
   215  		}
   216  	}
   217  	args = append(args, "--")
   218  	args = append(args, strings.Fields(os.Getenv("CGO_CPPFLAGS"))...)
   219  	args = append(args, bp.CgoCPPFLAGS...)
   220  	if len(bp.CgoPkgConfig) > 0 {
   221  		cmd := exec.Command("pkg-config", append([]string{"--cflags"}, bp.CgoPkgConfig...)...)
   222  		out, err := cmd.CombinedOutput()
   223  		if err != nil {
   224  			return nil, err
   225  		}
   226  		args = append(args, strings.Fields(string(out))...)
   227  	}
   228  	args = append(args, "-I", tmpdir)
   229  	args = append(args, strings.Fields(os.Getenv("CGO_CFLAGS"))...)
   230  	args = append(args, bp.CgoCFLAGS...)
   231  	args = append(args, bp.CgoFiles...)
   232  
   233  	cmd := exec.Command(args[0], args[1:]...)
   234  	cmd.Dir = bp.Dir
   235  	if err := cmd.Run(); err != nil {
   236  		return nil, err
   237  	}
   238  
   239  	return parser.ParseFile(p.fset, filepath.Join(tmpdir, "_cgo_gotypes.go"), nil, 0)
   240  }
   241  
   242  // context-controlled file system operations
   243  
   244  func (p *Importer) absPath(path string) (string, error) {
   245  	// TODO(gri) This should be using p.ctxt.AbsPath which doesn't
   246  	// exist but probably should. See also issue #14282.
   247  	return filepath.Abs(path)
   248  }
   249  
   250  func (p *Importer) isAbsPath(path string) bool {
   251  	if f := p.ctxt.IsAbsPath; f != nil {
   252  		return f(path)
   253  	}
   254  	return filepath.IsAbs(path)
   255  }
   256  
   257  func (p *Importer) joinPath(elem ...string) string {
   258  	if f := p.ctxt.JoinPath; f != nil {
   259  		return f(elem...)
   260  	}
   261  	return filepath.Join(elem...)
   262  }
   263  
   264  //go:linkname setUsesCgo go/types.srcimporter_setUsesCgo
   265  func setUsesCgo(conf *types.Config)
   266
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