all: update references to symbols moved from os to io/fs

The old os references are still valid, but update our code
to reflect best practices and get used to the new locations.

Code compiled with the bootstrap toolchain
(cmd/asm, cmd/dist, cmd/compile, debug/elf)
must remain Go 1.4-compatible and is excluded.

For #41190.

Change-Id: I8f9526977867c10a221e2f392f78d7dec073f1bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/243907
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

7 files changed, 41 insertions, 36 deletions

diff --git a/src/net/conf_test.go b/src/net/conf_test.go
index 3c7403eccc..4c21d56ba0 100644
--- a/src/net/conf_test.go
+++ b/src/net/conf_test.go
@@ -7,7 +7,7 @@
 package net
 
 import (
-	"os"
+	"io/fs"
 	"strings"
 	"testing"
 )
@@ -26,7 +26,7 @@ var defaultResolvConf = &dnsConfig{
 	ndots:    1,
 	timeout:  5,
 	attempts: 2,
-	err:      os.ErrNotExist,
+	err:      fs.ErrNotExist,
 }
 
 func TestConfHostLookupOrder(t *testing.T) {
@@ -106,7 +106,7 @@ func TestConfHostLookupOrder(t *testing.T) {
 			name: "solaris_no_nsswitch",
 			c: &conf{
 				goos:   "solaris",
-				nss:    &nssConf{err: os.ErrNotExist},
+				nss:    &nssConf{err: fs.ErrNotExist},
 				resolv: defaultResolvConf,
 			},
 			hostTests: []nssHostTest{{"google.com", "myhostname", hostLookupCgo}},
@@ -176,7 +176,7 @@ func TestConfHostLookupOrder(t *testing.T) {
 			name: "linux_no_nsswitch.conf",
 			c: &conf{
 				goos:   "linux",
-				nss:    &nssConf{err: os.ErrNotExist},
+				nss:    &nssConf{err: fs.ErrNotExist},
 				resolv: defaultResolvConf,
 			},
 			hostTests: []nssHostTest{{"google.com", "myhostname", hostLookupDNSFiles}},
diff --git a/src/net/dnsconfig_unix_test.go b/src/net/dnsconfig_unix_test.go
index 42880123c5..0d7897a813 100644
--- a/src/net/dnsconfig_unix_test.go
+++ b/src/net/dnsconfig_unix_test.go
@@ -8,6 +8,7 @@ package net
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"reflect"
 	"strings"
@@ -183,7 +184,7 @@ func TestDNSReadMissingFile(t *testing.T) {
 
 	conf := dnsReadConfig("a-nonexistent-file")
 	if !os.IsNotExist(conf.err) {
-		t.Errorf("missing resolv.conf:\ngot: %v\nwant: %v", conf.err, os.ErrNotExist)
+		t.Errorf("missing resolv.conf:\ngot: %v\nwant: %v", conf.err, fs.ErrNotExist)
 	}
 	conf.err = nil
 	want := &dnsConfig{
diff --git a/src/net/error_test.go b/src/net/error_test.go
index 62dfb9c15d..7823fdf9d8 100644
--- a/src/net/error_test.go
+++ b/src/net/error_test.go
@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"internal/poll"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net/internal/socktest"
 	"os"
@@ -97,7 +98,7 @@ second:
 	case *os.SyscallError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		nestedErr = err.Err
 		goto third
 	}
@@ -531,7 +532,7 @@ second:
 	case *os.SyscallError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		nestedErr = err.Err
 		goto third
 	}
@@ -546,7 +547,7 @@ third:
 		return nil
 	}
 	switch nestedErr {
-	case os.ErrClosed: // for Plan 9
+	case fs.ErrClosed: // for Plan 9
 		return nil
 	}
 	return fmt.Errorf("unexpected type on 3rd nested level: %T", nestedErr)
@@ -627,7 +628,7 @@ second:
 	case *os.SyscallError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		nestedErr = err.Err
 		goto third
 	}
@@ -706,7 +707,7 @@ second:
 	case *os.LinkError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError:
+	case *fs.PathError:
 		nestedErr = err.Err
 		goto third
 	}
@@ -799,7 +800,7 @@ func parseLookupPortError(nestedErr error) error {
 	switch nestedErr.(type) {
 	case *AddrError, *DNSError:
 		return nil
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		return nil
 	}
 	return fmt.Errorf("unexpected type on 1st nested level: %T", nestedErr)
diff --git a/src/net/http/example_filesystem_test.go b/src/net/http/example_filesystem_test.go
index e1fd42d049..0e81458a07 100644
--- a/src/net/http/example_filesystem_test.go
+++ b/src/net/http/example_filesystem_test.go
@@ -5,9 +5,9 @@
 package http_test
 
 import (
+	"io/fs"
 	"log"
 	"net/http"
-	"os"
 	"strings"
 )
 
@@ -33,7 +33,7 @@ type dotFileHidingFile struct {
 
 // Readdir is a wrapper around the Readdir method of the embedded File
 // that filters out all files that start with a period in their name.
-func (f dotFileHidingFile) Readdir(n int) (fis []os.FileInfo, err error) {
+func (f dotFileHidingFile) Readdir(n int) (fis []fs.FileInfo, err error) {
 	files, err := f.File.Readdir(n)
 	for _, file := range files { // Filters out the dot files
 		if !strings.HasPrefix(file.Name(), ".") {
@@ -52,12 +52,12 @@ type dotFileHidingFileSystem struct {
 // Open is a wrapper around the Open method of the embedded FileSystem
 // that serves a 403 permission error when name has a file or directory
 // with whose name starts with a period in its path.
-func (fs dotFileHidingFileSystem) Open(name string) (http.File, error) {
+func (fsys dotFileHidingFileSystem) Open(name string) (http.File, error) {
 	if containsDotFile(name) { // If dot file, return 403 response
-		return nil, os.ErrPermission
+		return nil, fs.ErrPermission
 	}
 
-	file, err := fs.FileSystem.Open(name)
+	file, err := fsys.FileSystem.Open(name)
 	if err != nil {
 		return nil, err
 	}
@@ -65,7 +65,7 @@ func (fs dotFileHidingFileSystem) Open(name string) (http.File, error) {
 }
 
 func ExampleFileServer_dotFileHiding() {
-	fs := dotFileHidingFileSystem{http.Dir(".")}
-	http.Handle("/", http.FileServer(fs))
+	fsys := dotFileHidingFileSystem{http.Dir(".")}
+	http.Handle("/", http.FileServer(fsys))
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }
diff --git a/src/net/http/fs.go b/src/net/http/fs.go
index d718fffba0..0743b5b621 100644
--- a/src/net/http/fs.go
+++ b/src/net/http/fs.go
@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"mime"
 	"mime/multipart"
 	"net/textproto"
@@ -43,7 +44,7 @@ type Dir string
 
 // mapDirOpenError maps the provided non-nil error from opening name
 // to a possibly better non-nil error. In particular, it turns OS-specific errors
-// about opening files in non-directories into os.ErrNotExist. See Issue 18984.
+// about opening files in non-directories into fs.ErrNotExist. See Issue 18984.
 func mapDirOpenError(originalErr error, name string) error {
 	if os.IsNotExist(originalErr) || os.IsPermission(originalErr) {
 		return originalErr
@@ -59,7 +60,7 @@ func mapDirOpenError(originalErr error, name string) error {
 			return originalErr
 		}
 		if !fi.IsDir() {
-			return os.ErrNotExist
+			return fs.ErrNotExist
 		}
 	}
 	return originalErr
@@ -98,8 +99,8 @@ type File interface {
 	io.Closer
 	io.Reader
 	io.Seeker
-	Readdir(count int) ([]os.FileInfo, error)
-	Stat() (os.FileInfo, error)
+	Readdir(count int) ([]fs.FileInfo, error)
+	Stat() (fs.FileInfo, error)
 }
 
 func dirList(w ResponseWriter, r *Request, f File) {
diff --git a/src/net/http/fs_test.go b/src/net/http/fs_test.go
index 4ac73b728f..de793b331e 100644
--- a/src/net/http/fs_test.go
+++ b/src/net/http/fs_test.go
@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"mime"
 	"mime/multipart"
@@ -629,9 +630,9 @@ func (f *fakeFileInfo) Sys() interface{}   { return nil }
 func (f *fakeFileInfo) ModTime() time.Time { return f.modtime }
 func (f *fakeFileInfo) IsDir() bool        { return f.dir }
 func (f *fakeFileInfo) Size() int64        { return int64(len(f.contents)) }
-func (f *fakeFileInfo) Mode() os.FileMode {
+func (f *fakeFileInfo) Mode() fs.FileMode {
 	if f.dir {
-		return 0755 | os.ModeDir
+		return 0755 | fs.ModeDir
 	}
 	return 0644
 }
@@ -644,12 +645,12 @@ type fakeFile struct {
 }
 
 func (f *fakeFile) Close() error               { return nil }
-func (f *fakeFile) Stat() (os.FileInfo, error) { return f.fi, nil }
-func (f *fakeFile) Readdir(count int) ([]os.FileInfo, error) {
+func (f *fakeFile) Stat() (fs.FileInfo, error) { return f.fi, nil }
+func (f *fakeFile) Readdir(count int) ([]fs.FileInfo, error) {
 	if !f.fi.dir {
-		return nil, os.ErrInvalid
+		return nil, fs.ErrInvalid
 	}
-	var fis []os.FileInfo
+	var fis []fs.FileInfo
 
 	limit := f.entpos + count
 	if count <= 0 || limit > len(f.fi.ents) {
@@ -668,11 +669,11 @@ func (f *fakeFile) Readdir(count int) ([]os.FileInfo, error) {
 
 type fakeFS map[string]*fakeFileInfo
 
-func (fs fakeFS) Open(name string) (File, error) {
+func (fsys fakeFS) Open(name string) (File, error) {
 	name = path.Clean(name)
-	f, ok := fs[name]
+	f, ok := fsys[name]
 	if !ok {
-		return nil, os.ErrNotExist
+		return nil, fs.ErrNotExist
 	}
 	if f.err != nil {
 		return nil, f.err
@@ -747,7 +748,7 @@ func TestDirectoryIfNotModified(t *testing.T) {
 	res.Body.Close()
 }
 
-func mustStat(t *testing.T, fileName string) os.FileInfo {
+func mustStat(t *testing.T, fileName string) fs.FileInfo {
 	fi, err := os.Stat(fileName)
 	if err != nil {
 		t.Fatal(err)
@@ -1081,7 +1082,7 @@ func (issue12991FS) Open(string) (File, error) { return issue12991File{}, nil }
 
 type issue12991File struct{ File }
 
-func (issue12991File) Stat() (os.FileInfo, error) { return nil, os.ErrPermission }
+func (issue12991File) Stat() (fs.FileInfo, error) { return nil, fs.ErrPermission }
 func (issue12991File) Close() error               { return nil }
 
 func TestServeContentErrorMessages(t *testing.T) {
@@ -1091,7 +1092,7 @@ func TestServeContentErrorMessages(t *testing.T) {
 			err: errors.New("random error"),
 		},
 		"/403": &fakeFileInfo{
-			err: &os.PathError{Err: os.ErrPermission},
+			err: &fs.PathError{Err: fs.ErrPermission},
 		},
 	}
 	ts := httptest.NewServer(FileServer(fs))
@@ -1289,7 +1290,7 @@ func (d fileServerCleanPathDir) Open(path string) (File, error) {
 		// Just return back something that's a directory.
 		return Dir(".").Open(".")
 	}
-	return nil, os.ErrNotExist
+	return nil, fs.ErrNotExist
 }
 
 type panicOnSeek struct{ io.ReadSeeker }
diff --git a/src/net/ipsock_plan9.go b/src/net/ipsock_plan9.go
index 23082366aa..7a4b7a6041 100644
--- a/src/net/ipsock_plan9.go
+++ b/src/net/ipsock_plan9.go
@@ -7,6 +7,7 @@ package net
 import (
 	"context"
 	"internal/bytealg"
+	"io/fs"
 	"os"
 	"syscall"
 )
@@ -164,7 +165,7 @@ func fixErr(err error) {
 	if nonNilInterface(oe.Addr) {
 		oe.Addr = nil
 	}
-	if pe, ok := oe.Err.(*os.PathError); ok {
+	if pe, ok := oe.Err.(*fs.PathError); ok {
 		if _, ok = pe.Err.(syscall.ErrorString); ok {
 			oe.Err = pe.Err
 		}