importer.go

Documentation: golang.org/x/tools/go/gcexportdata

     1  // Copyright 2016 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 gcexportdata
     6  
     7  import (
     8  	"fmt"
     9  	"go/token"
    10  	"go/types"
    11  	"os"
    12  )
    13  
    14  // NewImporter returns a new instance of the types.Importer interface
    15  // that reads type information from export data files written by gc.
    16  // The Importer also satisfies types.ImporterFrom.
    17  //
    18  // Export data files are located using "go build" workspace conventions
    19  // and the build.Default context.
    20  //
    21  // Use this importer instead of go/importer.For("gc", ...) to avoid the
    22  // version-skew problems described in the documentation of this package,
    23  // or to control the FileSet or access the imports map populated during
    24  // package loading.
    25  //
    26  // Deprecated: Use the higher-level API in golang.org/x/tools/go/packages,
    27  // which is more efficient.
    28  func NewImporter(fset *token.FileSet, imports map[string]*types.Package) types.ImporterFrom {
    29  	return importer{fset, imports}
    30  }
    31  
    32  type importer struct {
    33  	fset    *token.FileSet
    34  	imports map[string]*types.Package
    35  }
    36  
    37  func (imp importer) Import(importPath string) (*types.Package, error) {
    38  	return imp.ImportFrom(importPath, "", 0)
    39  }
    40  
    41  func (imp importer) ImportFrom(importPath, srcDir string, mode types.ImportMode) (_ *types.Package, err error) {
    42  	filename, path := Find(importPath, srcDir)
    43  	if filename == "" {
    44  		if importPath == "unsafe" {
    45  			// Even for unsafe, call Find first in case
    46  			// the package was vendored.
    47  			return types.Unsafe, nil
    48  		}
    49  		return nil, fmt.Errorf("can't find import: %s", importPath)
    50  	}
    51  
    52  	if pkg, ok := imp.imports[path]; ok && pkg.Complete() {
    53  		return pkg, nil // cache hit
    54  	}
    55  
    56  	// open file
    57  	f, err := os.Open(filename)
    58  	if err != nil {
    59  		return nil, err
    60  	}
    61  	defer func() {
    62  		f.Close()
    63  		if err != nil {
    64  			// add file name to error
    65  			err = fmt.Errorf("reading export data: %s: %v", filename, err)
    66  		}
    67  	}()
    68  
    69  	r, err := NewReader(f)
    70  	if err != nil {
    71  		return nil, err
    72  	}
    73  
    74  	return Read(r, imp.fset, imp.imports, path)
    75  }
    76
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