Fix false positive wit' InvalidVarsLintRule

If tharr bee nay variables in th' msgid, then "invalid" and "malform'd"
variables in th' msgstrr bee false positives.

Fixes #78

dennis/linter.py

@@ -449,6 +449,11 @@ def lint(self, vartok, linted_entry):
                 continue
 
             msgid_tokens = vartok.extract_tokens(' '.join(trstr.msgid_strings))
+            # If this is python-format or python-brace-format and there are
+            # no tokens in the msgid, then "no tokens, no problem".
+            if not msgid_tokens:
+                continue
+
             msgstr_tokens = vartok.extract_tokens(trstr.msgstr_string)
 
             invalid = msgstr_tokens.difference(msgid_tokens)

tests/test_linter.py

@@ -495,7 +495,7 @@ def test_fine(self):
     def test_invalid(self):
         linted_entry = build_linted_entry(
             '#: foo/foo.py:5\n'
-            'msgid "Foo"\n'
+            'msgid "Foo {bar}"\n'
             'msgstr "Oof: {foo}"\n')
 
         msgs = self.lintrule.lint(self.vartok, linted_entry)
@@ -564,6 +564,15 @@ def test_urlencoded_urls(self):
         msgs = self.lintrule.lint(self.vartok, linted_entry)
         assert len(msgs) == 0
 
+    def test_msgid_no_vars(self):
+        linted_entry = build_linted_entry(
+            '#: foo/foo.py:5\n'
+            'msgid "http://en.wikipedia.org/wiki/Canvas_element"\n'
+            'msgstr "http://it.wikipedia.org/wiki/Canvas_%28elemento_HTML%29"\n')
+
+        msgs = self.lintrule.lint(self.vartok, linted_entry)
+        assert len(msgs) == 0
+
 
 class TestBlankLintRule(LintRuleTestCase):
     lintrule = BlankLintRule()