io/ioutil: support predictable prefix,suffix for TempDir with *

Allow TempDir to create directories with predictable
prefixes and suffixes, separated by the last "*", for example:
    "prefix*suffix"
will now expand to
    "prefix" + <RANDOM_VALUE> + "suffix"

RELNOTE=yes

Fixes #33805.

Change-Id: I85fa73ae6a684ce820d1810c82a60765eb9c4a42
Reviewed-on: https://go-review.googlesource.com/c/go/+/198488
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/io/ioutil/example_test.go b/src/io/ioutil/example_test.go
index a7d340b77fa595a607dc2d4de1828a8742b241c3..bc2b6fba736098fe35997949592afe675415d652 100644 (file)
--- a/src/io/ioutil/example_test.go
+++ b/src/io/ioutil/example_test.go
@@ -53,6 +53,29 @@ func ExampleTempDir() {
        }
 }
 
+func ExampleTempDir_suffix() {
+       parentDir := os.TempDir()
+       logsDir, err := ioutil.TempDir(parentDir, "*-logs")
+       if err != nil {
+               log.Fatal(err)
+       }
+       defer os.RemoveAll(logsDir) // clean up
+
+       // Logs can be cleaned out earlier if needed by searching
+       // for all directories whose suffix ends in *-logs.
+       globPattern := filepath.Join(parentDir, "*-logs")
+       matches, err := filepath.Glob(globPattern)
+       if err != nil {
+               log.Fatalf("Failed to match %q: %v", globPattern, err)
+       }
+
+       for _, match := range matches {
+               if err := os.RemoveAll(match); err != nil {
+                       log.Printf("Failed to remove %q: %v", match, err)
+               }
+       }
+}
+
 func ExampleTempFile() {
        content := []byte("temporary file's content")
        tmpfile, err := ioutil.TempFile("", "example")

diff --git a/src/io/ioutil/tempfile.go b/src/io/ioutil/tempfile.go
index ba8783b9a0dc172e9d5b657cca5d39e0dc8b499b..3aa23c5f0173a2b188cbfacea4e64884be77f418 100644 (file)
--- a/src/io/ioutil/tempfile.go
+++ b/src/io/ioutil/tempfile.go
@@ -52,12 +52,7 @@ func TempFile(dir, pattern string) (f *os.File, err error) {
                dir = os.TempDir()
        }
 
-       var prefix, suffix string
-       if pos := strings.LastIndex(pattern, "*"); pos != -1 {
-               prefix, suffix = pattern[:pos], pattern[pos+1:]
-       } else {
-               prefix = pattern
-       }
+       prefix, suffix := prefixAndSuffix(pattern)
 
        nconflict := 0
        for i := 0; i < 10000; i++ {
@@ -76,21 +71,36 @@ func TempFile(dir, pattern string) (f *os.File, err error) {
        return
 }
 
-// TempDir creates a new temporary directory in the directory dir
-// with a name beginning with prefix and returns the path of the
-// new directory. If dir is the empty string, TempDir uses the
+// prefixAndSuffix splits pattern by the last wildcard "*", if applicable,
+// returning prefix as the part before "*" and suffix as the part after "*".
+func prefixAndSuffix(pattern string) (prefix, suffix string) {
+       if pos := strings.LastIndex(pattern, "*"); pos != -1 {
+               prefix, suffix = pattern[:pos], pattern[pos+1:]
+       } else {
+               prefix = pattern
+       }
+       return
+}
+
+// TempDir creates a new temporary directory in the directory dir.
+// The directory name is generated by taking pattern and applying a
+// random string to the end. If pattern includes a "*", the random string
+// replaces the last "*". TempDir returns the name of the new directory.
+// If dir is the empty string, TempDir uses the
 // default directory for temporary files (see os.TempDir).
 // Multiple programs calling TempDir simultaneously
 // will not choose the same directory. It is the caller's responsibility
 // to remove the directory when no longer needed.
-func TempDir(dir, prefix string) (name string, err error) {
+func TempDir(dir, pattern string) (name string, err error) {
        if dir == "" {
                dir = os.TempDir()
        }
 
+       prefix, suffix := prefixAndSuffix(pattern)
+
        nconflict := 0
        for i := 0; i < 10000; i++ {
-               try := filepath.Join(dir, prefix+nextRandom())
+               try := filepath.Join(dir, prefix+nextRandom()+suffix)
                err = os.Mkdir(try, 0700)
                if os.IsExist(err) {
                        if nconflict++; nconflict > 10 {

diff --git a/src/io/ioutil/tempfile_test.go b/src/io/ioutil/tempfile_test.go
index 0758890b6996efb9f9155032f5d21b100eab3bd7..698ebabee9e3feda2c7fd3463d9ad889baf528a4 100644 (file)
--- a/src/io/ioutil/tempfile_test.go
+++ b/src/io/ioutil/tempfile_test.go
@@ -54,18 +54,47 @@ func TestTempDir(t *testing.T) {
                t.Errorf("TempDir(`/_not_exists_`, `foo`) = %v, %v", name, err)
        }
 
-       dir := os.TempDir()
-       name, err = TempDir(dir, "ioutil_test")
-       if name == "" || err != nil {
-               t.Errorf("TempDir(dir, `ioutil_test`) = %v, %v", name, err)
+       tests := []struct {
+               pattern                string
+               wantPrefix, wantSuffix string
+       }{
+               {"ioutil_test", "ioutil_test", ""},
+               {"ioutil_test*", "ioutil_test", ""},
+               {"ioutil_test*xyz", "ioutil_test", "xyz"},
        }
-       if name != "" {
-               os.Remove(name)
-               re := regexp.MustCompile("^" + regexp.QuoteMeta(filepath.Join(dir, "ioutil_test")) + "[0-9]+$")
+
+       dir := os.TempDir()
+
+       runTestTempDir := func(t *testing.T, pattern, wantRePat string) {
+               name, err := TempDir(dir, pattern)
+               if name == "" || err != nil {
+                       t.Fatalf("TempDir(dir, `ioutil_test`) = %v, %v", name, err)
+               }
+               defer os.Remove(name)
+
+               re := regexp.MustCompile(wantRePat)
                if !re.MatchString(name) {
-                       t.Errorf("TempDir(`"+dir+"`, `ioutil_test`) created bad name %s", name)
+                       t.Errorf("TempDir(%q, %q) created bad name\n\t%q\ndid not match pattern\n\t%q", dir, pattern, name, wantRePat)
                }
        }
+
+       for _, tt := range tests {
+               t.Run(tt.pattern, func(t *testing.T) {
+                       wantRePat := "^" + regexp.QuoteMeta(filepath.Join(dir, tt.wantPrefix)) + "[0-9]+" + regexp.QuoteMeta(tt.wantSuffix) + "$"
+                       runTestTempDir(t, tt.pattern, wantRePat)
+               })
+       }
+
+       // Separately testing "*xyz" (which has no prefix). That is when constructing the
+       // pattern to assert on, as in the previous loop, using filepath.Join for an empty
+       // prefix filepath.Join(dir, ""), produces the pattern:
+       //     ^<DIR>[0-9]+xyz$
+       // yet we just want to match
+       //     "^<DIR>/[0-9]+xyz"
+       t.Run("*xyz", func(t *testing.T) {
+               wantRePat := "^" + regexp.QuoteMeta(filepath.Join(dir)) + regexp.QuoteMeta(string(filepath.Separator)) + "[0-9]+xyz$"
+               runTestTempDir(t, "*xyz", wantRePat)
+       })
 }
 
 // test that we return a nice error message if the dir argument to TempDir doesn't