Add write_to_tempfile back to fileutils

This was recently removed during graduation since I had stated
that only keystone was using the function. I was incorrect. It
seems that ceilometer and sahara are also using the function.

We should add it back so those projects can remove fileutils
from their oslo incubator project.

Change-Id: I661dd222da6386a7dbcf854958a63e59b13e9ba4

oslo_utils/fileutils.py

@@ -18,6 +18,7 @@ import errno
 import logging
 import os
 import stat
+import tempfile
 
 from oslo_utils import excutils
 
@@ -69,3 +70,30 @@ def remove_path_on_error(path, remove=delete_if_exists):
     except Exception:
         with excutils.save_and_reraise_exception():
             remove(path)
+
+
+def write_to_tempfile(content, path=None, suffix='', prefix='tmp'):
+    """Create temporary file or use existing file.
+
+    This util is needed for creating temporary file with
+    specified content, suffix and prefix. If path is not None,
+    it will be used for writing content. If the path doesn't
+    exist it'll be created.
+
+    :param content: content for temporary file.
+    :param path: same as parameter 'dir' for mkstemp
+    :param suffix: same as parameter 'suffix' for mkstemp
+    :param prefix: same as parameter 'prefix' for mkstemp
+
+    For example: it can be used in database tests for creating
+    configuration files.
+    """
+    if path:
+        ensure_tree(path)
+
+    (fd, path) = tempfile.mkstemp(suffix=suffix, dir=path, prefix=prefix)
+    try:
+        os.write(fd, content)
+    finally:
+        os.close(fd)
+    return path

oslo_utils/tests/test_fileutils.py

@@ -20,6 +20,7 @@ import stat
 import tempfile
 
 from oslotest import base as test_base
+import six
 
 from oslo_utils import fileutils
 
@@ -115,3 +116,73 @@ class RemovePathOnError(test_base.BaseTestCase):
                 raise Exception
         except Exception:
             self.assertFalse(os.path.exists(tmpdir))
+
+
+class WriteToTempfileTestCase(test_base.BaseTestCase):
+    def setUp(self):
+        super(WriteToTempfileTestCase, self).setUp()
+        self.content = 'testing123'.encode('ascii')
+
+    def check_file_content(self, path):
+        with open(path, 'r') as fd:
+            ans = fd.read()
+            self.assertEqual(self.content, six.b(ans))
+
+    def test_file_without_path_and_suffix(self):
+        res = fileutils.write_to_tempfile(self.content)
+        self.assertTrue(os.path.exists(res))
+
+        (basepath, tmpfile) = os.path.split(res)
+        self.assertTrue(basepath.startswith(tempfile.gettempdir()))
+        self.assertTrue(tmpfile.startswith('tmp'))
+
+        self.check_file_content(res)
+
+    def test_file_with_not_existing_path(self):
+        path = '/tmp/testing/test1'
+        res = fileutils.write_to_tempfile(self.content, path=path)
+        self.assertTrue(os.path.exists(res))
+        (basepath, tmpfile) = os.path.split(res)
+        self.assertEqual(basepath, path)
+        self.assertTrue(tmpfile.startswith('tmp'))
+
+        self.check_file_content(res)
+        shutil.rmtree('/tmp/testing')
+
+    def test_file_with_not_default_suffix(self):
+        suffix = '.conf'
+        res = fileutils.write_to_tempfile(self.content, suffix=suffix)
+        self.assertTrue(os.path.exists(res))
+
+        (basepath, tmpfile) = os.path.split(res)
+        self.assertTrue(basepath.startswith(tempfile.gettempdir()))
+        self.assertTrue(tmpfile.startswith('tmp'))
+        self.assertTrue(tmpfile.endswith('.conf'))
+
+        self.check_file_content(res)
+
+    def test_file_with_not_existing_path_and_not_default_suffix(self):
+        suffix = '.txt'
+        path = '/tmp/testing/test2'
+        res = fileutils.write_to_tempfile(self.content,
+                                          path=path,
+                                          suffix=suffix)
+        self.assertTrue(os.path.exists(res))
+        (basepath, tmpfile) = os.path.split(res)
+        self.assertTrue(tmpfile.startswith('tmp'))
+        self.assertEqual(basepath, path)
+        self.assertTrue(tmpfile.endswith(suffix))
+
+        self.check_file_content(res)
+        shutil.rmtree('/tmp/testing')
+
+    def test_file_with_not_default_prefix(self):
+        prefix = 'test'
+        res = fileutils.write_to_tempfile(self.content, prefix=prefix)
+        self.assertTrue(os.path.exists(res))
+
+        (basepath, tmpfile) = os.path.split(res)
+        self.assertTrue(tmpfile.startswith(prefix))
+        self.assertTrue(basepath.startswith(tempfile.gettempdir()))
+
+        self.check_file_content(res)