golang.org/x/tools@v0.21.1-0.20240520172518-788d39e776b1/go/buildutil/fakecontext.go (about)

     1  // Copyright 2015 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 buildutil
     6  
     7  import (
     8  	"fmt"
     9  	"go/build"
    10  	"io"
    11  	"os"
    12  	"path"
    13  	"path/filepath"
    14  	"sort"
    15  	"strings"
    16  	"time"
    17  )
    18  
    19  // FakeContext returns a build.Context for the fake file tree specified
    20  // by pkgs, which maps package import paths to a mapping from file base
    21  // names to contents.
    22  //
    23  // The fake Context has a GOROOT of "/go" and no GOPATH, and overrides
    24  // the necessary file access methods to read from memory instead of the
    25  // real file system.
    26  //
    27  // Unlike a real file tree, the fake one has only two levels---packages
    28  // and files---so ReadDir("/go/src/") returns all packages under
    29  // /go/src/ including, for instance, "math" and "math/big".
    30  // ReadDir("/go/src/math/big") would return all the files in the
    31  // "math/big" package.
    32  func FakeContext(pkgs map[string]map[string]string) *build.Context {
    33  	clean := func(filename string) string {
    34  		f := path.Clean(filepath.ToSlash(filename))
    35  		// Removing "/go/src" while respecting segment
    36  		// boundaries has this unfortunate corner case:
    37  		if f == "/go/src" {
    38  			return ""
    39  		}
    40  		return strings.TrimPrefix(f, "/go/src/")
    41  	}
    42  
    43  	ctxt := build.Default // copy
    44  	ctxt.GOROOT = "/go"
    45  	ctxt.GOPATH = ""
    46  	ctxt.Compiler = "gc"
    47  	ctxt.IsDir = func(dir string) bool {
    48  		dir = clean(dir)
    49  		if dir == "" {
    50  			return true // needed by (*build.Context).SrcDirs
    51  		}
    52  		return pkgs[dir] != nil
    53  	}
    54  	ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
    55  		dir = clean(dir)
    56  		var fis []os.FileInfo
    57  		if dir == "" {
    58  			// enumerate packages
    59  			for importPath := range pkgs {
    60  				fis = append(fis, fakeDirInfo(importPath))
    61  			}
    62  		} else {
    63  			// enumerate files of package
    64  			for basename := range pkgs[dir] {
    65  				fis = append(fis, fakeFileInfo(basename))
    66  			}
    67  		}
    68  		sort.Sort(byName(fis))
    69  		return fis, nil
    70  	}
    71  	ctxt.OpenFile = func(filename string) (io.ReadCloser, error) {
    72  		filename = clean(filename)
    73  		dir, base := path.Split(filename)
    74  		content, ok := pkgs[path.Clean(dir)][base]
    75  		if !ok {
    76  			return nil, fmt.Errorf("file not found: %s", filename)
    77  		}
    78  		return io.NopCloser(strings.NewReader(content)), nil
    79  	}
    80  	ctxt.IsAbsPath = func(path string) bool {
    81  		path = filepath.ToSlash(path)
    82  		// Don't rely on the default (filepath.Path) since on
    83  		// Windows, it reports virtual paths as non-absolute.
    84  		return strings.HasPrefix(path, "/")
    85  	}
    86  	return &ctxt
    87  }
    88  
    89  type byName []os.FileInfo
    90  
    91  func (s byName) Len() int           { return len(s) }
    92  func (s byName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
    93  func (s byName) Less(i, j int) bool { return s[i].Name() < s[j].Name() }
    94  
    95  type fakeFileInfo string
    96  
    97  func (fi fakeFileInfo) Name() string    { return string(fi) }
    98  func (fakeFileInfo) Sys() interface{}   { return nil }
    99  func (fakeFileInfo) ModTime() time.Time { return time.Time{} }
   100  func (fakeFileInfo) IsDir() bool        { return false }
   101  func (fakeFileInfo) Size() int64        { return 0 }
   102  func (fakeFileInfo) Mode() os.FileMode  { return 0644 }
   103  
   104  type fakeDirInfo string
   105  
   106  func (fd fakeDirInfo) Name() string    { return string(fd) }
   107  func (fakeDirInfo) Sys() interface{}   { return nil }
   108  func (fakeDirInfo) ModTime() time.Time { return time.Time{} }
   109  func (fakeDirInfo) IsDir() bool        { return true }
   110  func (fakeDirInfo) Size() int64        { return 0 }
   111  func (fakeDirInfo) Mode() os.FileMode  { return 0755 }