os: avoid nil returns from Readdirnames, Readdir, ReadDir
The refactoring of this code while adding ReadDir stopped
pre-allocating a 100-entry slice for the results.
That seemed like a good idea in general, since many
directories have nowhere near 100 entries, but it had the
side effect of returning a nil slice for an empty directory.
Some “golden” tests that are too sensitive about nil vs not
inside Google broke because Readdirnames(-1) was now
returning nil instead of []string{} on an empty directory.
It seems likely there are other such tests in the wild, and
it doesn't seem worth breaking them.
This commit restores the non-nil-ness of the old result,
without restoring the excessive preallocation.
Fixes #42367.
Change-Id: I2be72030ac703346e859a97c2d4e456fadfce9b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/267637
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>
diff --git a/src/os/dir.go b/src/os/dir.go
index b56d998..1d90b970 100644
--- a/src/os/dir.go
+++ b/src/os/dir.go
@@ -36,6 +36,12 @@
return nil, ErrInvalid
}
_, _, infos, err := f.readdir(n, readdirFileInfo)
+ if infos == nil {
+ // Readdir has historically always returned a non-nil empty slice, never nil,
+ // even on error (except misuse with nil receiver above).
+ // Keep it that way to avoid breaking overly sensitive callers.
+ infos = []FileInfo{}
+ }
return infos, err
}
@@ -59,6 +65,12 @@
return nil, ErrInvalid
}
names, _, _, err = f.readdir(n, readdirName)
+ if names == nil {
+ // Readdirnames has historically always returned a non-nil empty slice, never nil,
+ // even on error (except misuse with nil receiver above).
+ // Keep it that way to avoid breaking overly sensitive callers.
+ names = []string{}
+ }
return names, err
}
@@ -81,6 +93,10 @@
return nil, ErrInvalid
}
_, dirents, _, err := f.readdir(n, readdirDirEntry)
+ if dirents == nil {
+ // Match Readdir and Readdirnames: don't return nil slices.
+ dirents = []DirEntry{}
+ }
return dirents, err
}
diff --git a/src/os/os_test.go b/src/os/os_test.go
index 378ddf5..a1c0578 100644
--- a/src/os/os_test.go
+++ b/src/os/os_test.go
@@ -330,6 +330,9 @@
t.Error("could not find", m)
}
}
+ if s == nil {
+ t.Error("Readdirnames returned nil instead of empty slice")
+ }
}
func testReaddir(dir string, contents []string, t *testing.T) {
@@ -360,6 +363,9 @@
t.Error("could not find", m)
}
}
+ if s == nil {
+ t.Error("Readdir returned nil instead of empty slice")
+ }
}
func testReadDir(dir string, contents []string, t *testing.T) {
@@ -408,21 +414,27 @@
t.Error("could not find", m)
}
}
+ if s == nil {
+ t.Error("ReadDir returned nil instead of empty slice")
+ }
}
func TestReaddirnames(t *testing.T) {
testReaddirnames(".", dot, t)
testReaddirnames(sysdir.name, sysdir.files, t)
+ testReaddirnames(t.TempDir(), nil, t)
}
func TestReaddir(t *testing.T) {
testReaddir(".", dot, t)
testReaddir(sysdir.name, sysdir.files, t)
+ testReaddir(t.TempDir(), nil, t)
}
func TestReadDir(t *testing.T) {
testReadDir(".", dot, t)
testReadDir(sysdir.name, sysdir.files, t)
+ testReadDir(t.TempDir(), nil, t)
}
func benchmarkReaddirname(path string, b *testing.B) {
