Add a hacking rule for string interpolation at logging

String interpolation should be delayed to be handled
by the logging code, rather than being done
at the point of the logging call.
So add the following hacking rule for it.

- [N354] String interpolation should be delayed at logging calls.

See the oslo i18n guideline.

* http://docs.openstack.org/developer/oslo.i18n/guidelines.html

Change-Id: Ief6d3ee3539c0857098fffdb7acfeec3e0fed6eb
Closes-Bug: #1596829

1 files changed, 26 insertions, 0 deletions

diff --git a/nova/hacking/checks.py b/nova/hacking/checks.py
index e679b0c145..19c46f6747 100644
--- a/nova/hacking/checks.py
+++ b/nova/hacking/checks.py
@@ -105,6 +105,9 @@ doubled_words_re = re.compile(
     r"\b(then?|[iao]n|i[fst]|but|f?or|at|and|[dt]o)\s+\1\b")
 log_remove_context = re.compile(
     r"(.)*LOG\.(.*)\(.*(context=[_a-zA-Z0-9].*)+.*\)")
+log_string_interpolation = re.compile(r".*LOG\.(error|warning|info"
+                                      r"|critical|exception|debug)"
+                                      r"\([^,]*%[^,]*[,)]")
 
 
 class BaseASTChecker(ast.NodeVisitor):
@@ -794,6 +797,28 @@ def check_context_log(logical_line, physical_line, filename):
               "kwarg.")
 
 
+def check_delayed_string_interpolation(logical_line, physical_line, filename):
+    """Check whether string interpolation is delayed at logging calls
+
+    Not correct: LOG.debug('Example: %s' % 'bad')
+    Correct:     LOG.debug('Example: %s', 'good')
+
+    N354
+    """
+    if "nova/tests" in filename:
+        return
+
+    if pep8.noqa(physical_line):
+        return
+
+    if log_string_interpolation.match(logical_line):
+        yield(logical_line.index('%'),
+              "N354: String interpolation should be delayed to be "
+              "handled by the logging code, rather than being done "
+              "at the point of the logging call. "
+              "Use ',' instead of '%'.")
+
+
 def factory(register):
     register(import_no_db_in_virt)
     register(no_db_session_in_public_api)
@@ -834,3 +859,4 @@ def factory(register):
     register(no_log_warn)
     register(CheckForUncalledTestClosure)
     register(check_context_log)
+    register(check_delayed_string_interpolation)