starlark/module: os add temp_dir function

starlark/module/os/os.go

@@ -25,6 +25,7 @@ const (
 	RemoveFuncName    = "remove"
 	RemoveAllFuncName = "remove_all"
 	RenameFuncName    = "rename"
+	TempDirFuncName   = "temp_dir"
 )
 
 var (
@@ -55,6 +56,7 @@ func LoadModule() (starlark.StringDict, error) {
 					RemoveFuncName:    starlark.NewBuiltin(MkdirFuncName, Remove),
 					RemoveAllFuncName: starlark.NewBuiltin(MkdirFuncName, RemoveAll),
 					RenameFuncName:    starlark.NewBuiltin(RenameFuncName, Rename),
+					TempDirFuncName:   starlark.NewBuiltin(TempDirFuncName, TempDir),
 				},
 			},
 		}
@@ -323,3 +325,13 @@ func Rename(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, k
 
 	return starlark.None, os.Rename(oldpath, newpath)
 }
+
+// TempDir returns the default directory to use for temporary files.
+//
+//   outline: os
+//     functions:
+//       temp_dir()
+//         returns the default directory to use for temporary files.
+func TempDir(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+	return starlark.String(os.TempDir()), nil
+}

starlark/module/os/testdata/test.star

@@ -1,6 +1,8 @@
 load('os', 'os')
 load('assert.star', 'assert')
 
+assert.ne(os.temp_dir(), "")
+
 key = "HELLO"
 value = "world"
 
@@ -9,21 +11,19 @@ assert.eq(os.getenv(key), value)
 
 content = "hello world\n"
 
-assert.eq(os.write_file("/tmp/plain.txt", content), None)
-assert.eq(os.read_file("/tmp/plain.txt"), content)
+temp = os.temp_dir()
+os.chdir(temp)
+assert.eq(os.getwd(), temp)
 
-assert.eq(os.write_file("/tmp/perms.txt", content=content, perms=0o777), None)
-assert.eq(os.read_file("/tmp/perms.txt"), content)
+assert.eq(os.write_file("plain.txt", content), None)
+assert.eq(os.read_file("plain.txt"), content)
+
+assert.eq(os.write_file("perms.txt", content=content, perms=0o777), None)
+assert.eq(os.read_file("perms.txt"), content)
 
 os.mkdir("foo", 0o755)
 os.remove("foo")
 
-assert.ne(os.getwd(), "")
-
-home = os.getenv("HOME")
-os.chdir(home)
-assert.eq(os.getwd(), home)
-
 os.mkdir_all("foo/bar", 0o755)
 
 os.rename("foo", "bar")