Add module 'write-files-deferred' executed in stage 'final' (#916)

The main idea is to introduce a second module that takes care of
writing files, but in the 'final' stage.

While the introduction of a second module would allow for choosing
the appropriate place withing the order of modules (and stages),
there is no addition top-level directive being added to the cloud
configuration schema. Instead, 'write-files' schema is being extended
to include a 'defer' attribute used only by the 'write-deffered-files'
modules.

The new module 'write-deferred-files' reuses as much as
possible of the 'write-files' functionality.

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/integration_tests/modules/test_write_files.py b/tests/integration_tests/modules/test_write_files.py
index 15832ae3..1d532fac 100644
--- a/tests/integration_tests/modules/test_write_files.py
+++ b/tests/integration_tests/modules/test_write_files.py
@@ -21,6 +21,9 @@ B64_CONTENT = base64.b64encode(ASCII_TEXT.encode("utf-8"))
 #
 USER_DATA = """\
 #cloud-config
+users:
+-   default
+-   name: myuser
 write_files:
 -   encoding: b64
     content: {}
@@ -41,6 +44,12 @@ write_files:
         H4sIAIDb/U8C/1NW1E/KzNMvzuBKTc7IV8hIzcnJVyjPL8pJ4QIA6N+MVxsAAAA=
     path: /root/file_gzip
     permissions: '0755'
+-   path: '/home/testuser/my-file'
+    content: |
+      echo 'hello world!'
+    defer: true
+    owner: 'myuser'
+    permissions: '0644'
 """.format(B64_CONTENT.decode("ascii"))
 
 
@@ -64,3 +73,15 @@ class TestWriteFiles:
     def test_write_files(self, cmd, expected_out, class_client):
         out = class_client.execute(cmd)
         assert expected_out in out
+
+    def test_write_files_deferred(self, class_client):
+        """Test that write files deferred works as expected.
+
+        Users get created after write_files module runs, so ensure that
+        with `defer: true`, the file gets written with correct ownership.
+        """
+        out = class_client.read_from_file("/home/testuser/my-file")
+        assert "echo 'hello world!'" == out
+        assert class_client.execute(
+            'stat -c "%U %a" /home/testuser/my-file'
+        ) == 'myuser 644'