all: remove os.ErrTemporary

As discussed in
https://github.com/golang/go/issues/32463#issuecomment-506833421
the classification of deadline-based timeouts as "temporary" errors is a
historical accident. I/O timeouts used to be duration-based, so they
really were temporary--retrying a timed-out operation could succeed. Now
that they're deadline-based, timeouts aren't temporary unless you reset
the deadline.

Drop ErrTemporary from Go 1.13, since its definition is wrong. We'll
consider putting it back in Go 1.14 with a clear definition and
deprecate net.OpError.Temporary.

Fixes #32463

Change-Id: I70cda664590d8872541e17409a5780da76920891
Reviewed-on: https://go-review.googlesource.com/c/go/+/188398
Reviewed-by: Jonathan Amsterdam <jba@google.com>

16 files changed, 17 insertions, 70 deletions

diff --git a/api/go1.13.txt b/api/go1.13.txt
index 16f11cf2b7..a8e39ce8ea 100644
--- a/api/go1.13.txt
+++ b/api/go1.13.txt
@@ -237,7 +237,6 @@ pkg os (netbsd-arm64), const O_SYNC = 128
 pkg os (netbsd-arm64), const O_TRUNC = 1024
 pkg os (netbsd-arm64), const PathListSeparator = 58
 pkg os (netbsd-arm64), const PathSeparator = 47
-pkg os, var ErrTemporary error
 pkg os, var ErrTimeout error
 pkg path/filepath (netbsd-arm64-cgo), const ListSeparator = 58
 pkg path/filepath (netbsd-arm64-cgo), const Separator = 47
diff --git a/src/context/context.go b/src/context/context.go
index 05d01d0294..b400396513 100644
--- a/src/context/context.go
+++ b/src/context/context.go
@@ -164,7 +164,7 @@ func (deadlineExceededError) Error() string   { return "context deadline exceede
 func (deadlineExceededError) Timeout() bool   { return true }
 func (deadlineExceededError) Temporary() bool { return true }
 func (deadlineExceededError) Is(target error) bool {
-	return target == oserror.ErrTimeout || target == oserror.ErrTemporary
+	return target == oserror.ErrTimeout
 }
 
 // An emptyCtx is never canceled, has no values, and has no deadline. It is not
diff --git a/src/internal/oserror/errors.go b/src/internal/oserror/errors.go
index 8bd17c8b56..8fccc95482 100644
--- a/src/internal/oserror/errors.go
+++ b/src/internal/oserror/errors.go
@@ -15,7 +15,6 @@ var (
 	ErrExist      = errors.New("file already exists")
 	ErrNotExist   = errors.New("file does not exist")
 	ErrClosed     = errors.New("file already closed")
-	ErrTemporary  = temporaryError{}
 	ErrTimeout    = timeoutError{}
 )
 
@@ -45,20 +44,3 @@ func IsTimeout(err error) bool {
 	}
 	return false
 }
-
-// IsTemporary reports whether err indicates a temporary condition.
-func IsTemporary(err error) bool {
-	for err != nil {
-		if err == ErrTemporary {
-			return true
-		}
-		if x, ok := err.(interface{ Temporary() bool }); ok {
-			return x.Temporary()
-		}
-		if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(ErrTemporary) {
-			return true
-		}
-		err = errors.Unwrap(err)
-	}
-	return false
-}
diff --git a/src/internal/oserror/errors_test.go b/src/internal/oserror/errors_test.go
index 6d6a56a0c7..bf3e057ccf 100644
--- a/src/internal/oserror/errors_test.go
+++ b/src/internal/oserror/errors_test.go
@@ -9,15 +9,13 @@ import (
 )
 
 type ttError struct {
-	timeout   bool
-	temporary bool
+	timeout bool
 }
 
 func (e ttError) Error() string {
-	return fmt.Sprintf("ttError{timeout:%v temporary:%v}", e.timeout, e.temporary)
+	return fmt.Sprintf("ttError{timeout:%v}", e.timeout)
 }
-func (e ttError) Timeout() bool   { return e.timeout }
-func (e ttError) Temporary() bool { return e.temporary }
+func (e ttError) Timeout() bool { return e.timeout }
 
 type isError struct {
 	err error
@@ -43,21 +41,3 @@ func TestIsTimeout(t *testing.T) {
 		}
 	}
 }
-
-func TestIsTemporary(t *testing.T) {
-	for _, test := range []struct {
-		want bool
-		err  error
-	}{
-		{true, ttError{temporary: true}},
-		{true, isError{os.ErrTemporary}},
-		{true, os.ErrTemporary},
-		{true, fmt.Errorf("wrap: %w", os.ErrTemporary)},
-		{false, ttError{temporary: false}},
-		{false, errors.New("error")},
-	} {
-		if got, want := oserror.IsTemporary(test.err), test.want; got != want {
-			t.Errorf("IsTemporary(err) = %v, want %v\n%+v", got, want, test.err)
-		}
-	}
-}
diff --git a/src/internal/poll/fd.go b/src/internal/poll/fd.go
index 784bea4b5a..5009e2671b 100644
--- a/src/internal/poll/fd.go
+++ b/src/internal/poll/fd.go
@@ -48,7 +48,7 @@ func (e *TimeoutError) Timeout() bool   { return true }
 func (e *TimeoutError) Temporary() bool { return true }
 
 func (e *TimeoutError) Is(target error) bool {
-	return target == oserror.ErrTimeout || target == oserror.ErrTemporary
+	return target == oserror.ErrTimeout
 }
 
 // ErrNotPollable is returned when the file or socket is not suitable
diff --git a/src/net/cgo_unix.go b/src/net/cgo_unix.go
index b9a6ffaa60..c31cbfd814 100644
--- a/src/net/cgo_unix.go
+++ b/src/net/cgo_unix.go
@@ -40,8 +40,6 @@ func (eai addrinfoErrno) Timeout() bool   { return false }
 
 func (eai addrinfoErrno) Is(target error) bool {
 	switch target {
-	case os.ErrTemporary:
-		return eai.Temporary()
 	case os.ErrTimeout:
 		return eai.Timeout()
 	}
diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index 2f9bdc2700..e3a1a10cc6 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -2288,8 +2288,6 @@ func (e *httpError) Is(target error) bool {
 	switch target {
 	case os.ErrTimeout:
 		return e.timeout
-	case os.ErrTemporary:
-		return true
 	}
 	return false
 }
@@ -2629,7 +2627,7 @@ func (tlsHandshakeTimeoutError) Temporary() bool { return true }
 func (tlsHandshakeTimeoutError) Error() string   { return "net/http: TLS handshake timeout" }
 
 func (tlsHandshakeTimeoutError) Is(target error) bool {
-	return target == os.ErrTimeout || target == os.ErrTemporary
+	return target == os.ErrTimeout
 }
 
 // fakeLocker is a sync.Locker which does nothing. It's used to guard
diff --git a/src/net/net.go b/src/net/net.go
index b3f9b8ba07..54e1ac383a 100644
--- a/src/net/net.go
+++ b/src/net/net.go
@@ -518,8 +518,6 @@ func (e *OpError) Temporary() bool {
 
 func (e *OpError) Is(target error) bool {
 	switch target {
-	case os.ErrTemporary:
-		return e.Temporary()
 	case os.ErrTimeout:
 		return e.Timeout()
 	}
@@ -619,8 +617,6 @@ func (e *DNSError) Temporary() bool { return e.IsTimeout || e.IsTemporary }
 
 func (e *DNSError) Is(target error) bool {
 	switch target {
-	case os.ErrTemporary:
-		return e.Temporary()
 	case os.ErrTimeout:
 		return e.Timeout()
 	}
diff --git a/src/net/pipe.go b/src/net/pipe.go
index 8cc127464b..5abc4aabe6 100644
--- a/src/net/pipe.go
+++ b/src/net/pipe.go
@@ -86,7 +86,7 @@ func (timeoutError) Timeout() bool   { return true }
 func (timeoutError) Temporary() bool { return true }
 
 func (timeoutError) Is(target error) bool {
-	return target == os.ErrTemporary || target == os.ErrTimeout
+	return target == os.ErrTimeout
 }
 
 type pipeAddr struct{}
diff --git a/src/net/url/url.go b/src/net/url/url.go
index 7f6ff93ce4..3212b9e998 100644
--- a/src/net/url/url.go
+++ b/src/net/url/url.go
@@ -26,10 +26,16 @@ type Error struct {
 	Err error
 }
 
-func (e *Error) Unwrap() error   { return e.Err }
-func (e *Error) Error() string   { return e.Op + " " + e.URL + ": " + e.Err.Error() }
-func (e *Error) Timeout() bool   { return oserror.IsTimeout(e.Err) }
-func (e *Error) Temporary() bool { return oserror.IsTemporary(e.Err) }
+func (e *Error) Unwrap() error { return e.Err }
+func (e *Error) Error() string { return e.Op + " " + e.URL + ": " + e.Err.Error() }
+func (e *Error) Timeout() bool { return oserror.IsTimeout(e.Err) }
+
+func (e *Error) Temporary() bool {
+	t, ok := e.Err.(interface {
+		Temporary() bool
+	})
+	return ok && t.Temporary()
+}
 
 func ishex(c byte) bool {
 	switch {
diff --git a/src/os/error.go b/src/os/error.go
index 0c2e6a7322..4cf35f2b77 100644
--- a/src/os/error.go
+++ b/src/os/error.go
@@ -23,7 +23,6 @@ var (
 	ErrNotExist   = errNotExist()   // "file does not exist"
 	ErrClosed     = errClosed()     // "file already closed"
 	ErrTimeout    = errTimeout()    // "deadline exceeded"
-	ErrTemporary  = errTemporary()  // "temporary error"
 	ErrNoDeadline = errNoDeadline() // "file type does not support deadline"
 )
 
@@ -33,7 +32,6 @@ func errExist() error      { return oserror.ErrExist }
 func errNotExist() error   { return oserror.ErrNotExist }
 func errClosed() error     { return oserror.ErrClosed }
 func errTimeout() error    { return oserror.ErrTimeout }
-func errTemporary() error  { return oserror.ErrTemporary }
 func errNoDeadline() error { return poll.ErrNoDeadline }
 
 type timeout interface {
diff --git a/src/syscall/syscall_js.go b/src/syscall/syscall_js.go
index 99f9a935fe..6db01c32f1 100644
--- a/src/syscall/syscall_js.go
+++ b/src/syscall/syscall_js.go
@@ -58,8 +58,6 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTemporary:
-		return e.Temporary()
 	case oserror.ErrTimeout:
 		return e.Timeout()
 	case oserror.ErrPermission:
diff --git a/src/syscall/syscall_nacl.go b/src/syscall/syscall_nacl.go
index 3fc504fd9f..33ad8bfab0 100644
--- a/src/syscall/syscall_nacl.go
+++ b/src/syscall/syscall_nacl.go
@@ -65,8 +65,6 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTemporary:
-		return e.Temporary()
 	case oserror.ErrTimeout:
 		return e.Timeout()
 	case oserror.ErrPermission:
diff --git a/src/syscall/syscall_plan9.go b/src/syscall/syscall_plan9.go
index 9b5a2940b0..d1b4bd9bd5 100644
--- a/src/syscall/syscall_plan9.go
+++ b/src/syscall/syscall_plan9.go
@@ -29,8 +29,6 @@ func NewError(s string) error { return ErrorString(s) }
 
 func (e ErrorString) Is(target error) bool {
 	switch target {
-	case oserror.ErrTemporary:
-		return e.Temporary()
 	case oserror.ErrTimeout:
 		return e.Timeout()
 	case oserror.ErrPermission:
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
index 1b66e3bb11..4bb7799d53 100644
--- a/src/syscall/syscall_unix.go
+++ b/src/syscall/syscall_unix.go
@@ -121,8 +121,6 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTemporary:
-		return e.Temporary()
 	case oserror.ErrTimeout:
 		return e.Timeout()
 	case oserror.ErrPermission:
diff --git a/src/syscall/syscall_windows.go b/src/syscall/syscall_windows.go
index 6201b6475d..aa4cfa7243 100644
--- a/src/syscall/syscall_windows.go
+++ b/src/syscall/syscall_windows.go
@@ -115,8 +115,6 @@ const _ERROR_BAD_NETPATH = Errno(53)
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTemporary:
-		return e.Temporary()
 	case oserror.ErrTimeout:
 		return e.Timeout()
 	case oserror.ErrPermission: