Fixed #19552 -- Enhanced makemessages handling of ``{# #}``-style template comments.

They are simply ignored now. This allows for a more correct behavior when
they are placed before translatable constructs on the same line.

Previously, the latter were wrongly ignored because the former were
preserved when converting template code to the internal Python-syntax
form later fed to xgettext but Python has no ``/* ... */``-style
comments.

Also, special comments directed to translators are now only taken in
account when they are located at the end of a line. e.g.::

  {# Translators: ignored #}{% trans "Literal A" %}{# Translators: valid, associated with "Literal B" below #}
  {% trans "Literal B" %}

Behavior of ``{% comment %}...{% endcomment %}``tags remains unchanged.

Thanks juneih at redpill-linpro dot com for the report and Claude for
his work on the issue.

django/utils/translation/__init__.py

@@ -21,6 +21,11 @@ __all__ = [
     'npgettext', 'npgettext_lazy',
 ]
 
+
+class TranslatorCommentWarning(SyntaxWarning):
+    pass
+
+
 # Here be dragons, so a short explanation of the logic won't hurt:
 # We are trying to solve two problems: (1) access settings, in particular
 # settings.USE_I18N, as late as possible, so that modules can be imported

django/utils/translation/trans_real.py

@@ -7,6 +7,7 @@ import re
 import sys
 import gettext as gettext_module
 from threading import local
+import warnings
 
 from django.utils.importlib import import_module
 from django.utils.encoding import force_str, force_text
@@ -14,6 +15,7 @@ from django.utils._os import upath
 from django.utils.safestring import mark_safe, SafeData
 from django.utils import six
 from django.utils.six import StringIO
+from django.utils.translation import TranslatorCommentWarning
 
 
 # Translations are cached in a dictionary for every language+app tuple.
@@ -41,6 +43,7 @@ accept_language_re = re.compile(r'''
 
 language_code_prefix_re = re.compile(r'^/([\w-]+)(/|$)')
 
+
 def to_locale(language, to_lower=False):
     """
     Turns a language name (en-us) into a locale name (en_US). If 'to_lower' is
@@ -468,6 +471,9 @@ def templatize(src, origin=None):
     plural = []
     incomment = False
     comment = []
+    lineno_comment_map = {}
+    comment_lineno_cache = None
+
     for t in Lexer(src, origin).tokenize():
         if incomment:
             if t.token_type == TOKEN_BLOCK and t.contents == 'endcomment':
@@ -529,7 +535,27 @@ def templatize(src, origin=None):
                     plural.append(contents)
                 else:
                     singular.append(contents)
+
         else:
+            # Handle comment tokens (`{# ... #}`) plus other constructs on
+            # the same line:
+            if comment_lineno_cache is not None:
+                cur_lineno = t.lineno + t.contents.count('\n')
+                if comment_lineno_cache == cur_lineno:
+                    if t.token_type != TOKEN_COMMENT:
+                        for c in lineno_comment_map[comment_lineno_cache]:
+                            filemsg = ''
+                            if origin:
+                                filemsg = 'file %s, ' % origin
+                            warn_msg = ("The translator-targeted comment '%s' "
+                                "(%sline %d) was ignored, because it wasn't the last item "
+                                "on the line.") % (c, filemsg, comment_lineno_cache)
+                            warnings.warn(warn_msg, TranslatorCommentWarning)
+                        lineno_comment_map[comment_lineno_cache] = []
+                else:
+                    out.write('# %s' % ' | '.join(lineno_comment_map[comment_lineno_cache]))
+                comment_lineno_cache = None
+
             if t.token_type == TOKEN_BLOCK:
                 imatch = inline_re.match(t.contents)
                 bmatch = block_re.match(t.contents)
@@ -586,7 +612,10 @@ def templatize(src, origin=None):
                     else:
                         out.write(blankout(p, 'F'))
             elif t.token_type == TOKEN_COMMENT:
-                out.write(' # %s' % t.contents)
+                if t.contents.lstrip().startswith(TRANSLATOR_COMMENT_MARK):
+                    lineno_comment_map.setdefault(t.lineno,
+                                                  []).append(t.contents)
+                    comment_lineno_cache = t.lineno
             else:
                 out.write(blankout(t.contents, 'X'))
     return force_str(out.getvalue())

docs/releases/1.6.txt

@@ -47,6 +47,26 @@ Backwards incompatible changes in 1.6
   should review it as ``type='text'`` widgets might be now output as
   ``type='email'`` or ``type='url'`` depending on their corresponding field type.
 
+* Extraction of translatable literals from templates with the
+  :djadmin:`makemessages` command now correctly detects i18n constructs when
+  they are located after a ``{#`` / ``#}``-type comment on the same line. E.g.:
+
+  .. code-block:: html+django
+
+    {# A comment #}{% trans "This literal was incorrectly ignored. Not anymore" %}
+
+* (Related to the above item.) Validation of the placement of
+  :ref:`translator-comments-in-templates` specified using ``{#`` / ``#}`` is now
+  stricter. All translator comments not located at the end of their respective
+  lines in a template are ignored and a warning is generated by
+  :djadmin:`makemessages` when it finds them. E.g.:
+
+  .. code-block:: html+django
+
+    {# Translators: This is ignored #}{% trans "Translate me" %}
+    {{ title }}{# Translators: Extracted and associated with 'Welcome' below #}
+    <h1>{% trans "Welcome" %}</h1>
+
 .. warning::
 
     In addition to the changes outlined in this section, be sure to review the

docs/topics/i18n/translation.txt

@@ -142,14 +142,22 @@ preceding the string, e.g.::
         # Translators: This message appears on the home page only
         output = ugettext("Welcome to my site.")
 
-This also works in templates with the :ttag:`comment` tag:
+The comment will then appear in the resulting ``.po`` file associated with the
+translatable contruct located below it and should also be displayed by most
+translation tools.
 
-.. code-block:: html+django
+.. note:: Just for completeness, this is the corresponding fragment of the
+    resulting ``.po`` file:
+
+    .. code-block:: po
 
-    {% comment %}Translators: This is a text of the base template {% endcomment %}
+        #. Translators: This message appears on the home page only
+        # path/to/python/file.py:123
+        msgid "Welcome to my site."
+        msgstr ""
 
-The comment will then appear in the resulting ``.po`` file and should also be
-displayed by most translation tools.
+This also works in templates. See :ref:`translator-comments-in-templates` for
+more details.
 
 Marking strings as no-op
 ------------------------
@@ -620,6 +628,63 @@ markers<contextual-markers>` using the ``context`` keyword:
 
     {% blocktrans with name=user.username context "greeting" %}Hi {{ name }}{% endblocktrans %}
 
+.. _translator-comments-in-templates:
+
+Comments for translators in templates
+-------------------------------------
+
+Just like with :ref:`Python code <translator-comments>`, these notes for
+translators can be specified using comments, either with the :ttag:`comment`
+tag:
+
+.. code-block:: html+django
+
+    {% comment %}Translators: View verb{% endcomment %}
+    {% trans "View" %}
+
+    {% comment %}Translators: Short intro blurb{% endcomment %}
+    <p>{% blocktrans %}A multiline translatable
+    literal.{% endblocktrans %}</p>
+
+or with the ``{#`` ... ``#}`` :ref:`one-line comment constructs <template-comments>`:
+
+.. code-block:: html+django
+
+    {# Translators: Label of a button that triggers search{% endcomment #}
+    <button type="submit">{% trans "Go" %}</button>
+
+    {# Translators: This is a text of the base template #}
+    {% blocktrans %}Ambiguous translatable block of text{% endtransblock %}
+
+.. note:: Just for completeness, these are the corresponding fragments of the
+    resulting ``.po`` file:
+
+    .. code-block:: po
+
+        #. Translators: View verb
+        # path/to/template/file.html:10
+        msgid "View"
+        msgstr ""
+
+        #. Translators: Short intro blurb
+        # path/to/template/file.html:13
+        msgid ""
+        "A multiline translatable"
+        "literal."
+        msgstr ""
+
+        # ...
+
+        #. Translators: Label of a button that triggers search
+        # path/to/template/file.html:100
+        msgid "Go"
+        msgstr ""
+
+        #. Translators:
+        # path/to/template/file.html:103
+        msgid "Ambiguous translatable block of text"
+        msgstr ""
+
 .. _template-translation-vars:
 
 Other tags

docs/topics/templates.txt

@@ -250,6 +250,8 @@ You can also create your own custom template tags; see
     tags and filters available for a given site. See
     :doc:`/ref/contrib/admin/admindocs`.
 
+.. _template-comments:
+
 Comments
 ========
 

tests/regressiontests/i18n/commands/extraction.py

@@ -4,6 +4,7 @@ from __future__ import unicode_literals
 import os
 import re
 import shutil
+import warnings
 
 from django.core import management
 from django.test import SimpleTestCase
@@ -11,6 +12,7 @@ from django.utils.encoding import force_text
 from django.utils._os import upath
 from django.utils import six
 from django.utils.six import StringIO
+from django.utils.translation import TranslatorCommentWarning
 
 
 LOCALE='de'
@@ -120,6 +122,7 @@ class BasicExtractorTests(ExtractorTests):
         self.assertFalse(os.path.exists('./templates/template_with_error.tpl.py'))
 
     def test_extraction_warning(self):
+        """test xgettext warning about multiple bare interpolation placeholders"""
         os.chdir(self.test_dir)
         shutil.copyfile('./code.sample', './code_sample.py')
         stdout = StringIO()
@@ -172,6 +175,63 @@ class BasicExtractorTests(ExtractorTests):
             self.assertTrue('msgctxt "Special blocktrans context wrapped in double quotes"' in po_contents)
             self.assertTrue('msgctxt "Special blocktrans context wrapped in single quotes"' in po_contents)
 
+    def test_template_comments(self):
+        """Template comment tags on the same line of other constructs (#19552)"""
+        os.chdir(self.test_dir)
+        # Test detection/end user reporting of old, incorrect templates
+        # translator comments syntax
+        with warnings.catch_warnings(record=True) as ws:
+            warnings.simplefilter('always')
+            management.call_command('makemessages', locale=LOCALE, extensions=['thtml'], verbosity=0)
+            self.assertEqual(len(ws), 3)
+            for w in ws:
+                self.assertTrue(issubclass(w.category, TranslatorCommentWarning))
+            six.assertRegex(self, str(ws[0].message),
+                r"The translator-targeted comment 'Translators: ignored i18n comment #1' \(file templates/comments.thtml, line 4\) was ignored, because it wasn't the last item on the line\."
+            )
+            six.assertRegex(self, str(ws[1].message),
+                r"The translator-targeted comment 'Translators: ignored i18n comment #3' \(file templates/comments.thtml, line 6\) was ignored, because it wasn't the last item on the line\."
+            )
+            six.assertRegex(self, str(ws[2].message),
+                r"The translator-targeted comment 'Translators: ignored i18n comment #4' \(file templates/comments.thtml, line 8\) was ignored, because it wasn't the last item on the line\."
+            )
+        # Now test .po file contents
+        self.assertTrue(os.path.exists(self.PO_FILE))
+        with open(self.PO_FILE, 'r') as fp:
+            po_contents = force_text(fp.read())
+
+            self.assertMsgId('Translatable literal #9a', po_contents)
+            self.assertFalse('ignored comment #1' in po_contents)
+
+            self.assertFalse('Translators: ignored i18n comment #1' in po_contents)
+            self.assertMsgId("Translatable literal #9b", po_contents)
+
+            self.assertFalse('ignored i18n comment #2' in po_contents)
+            self.assertFalse('ignored comment #2' in po_contents)
+            self.assertMsgId('Translatable literal #9c', po_contents)
+
+            self.assertFalse('ignored comment #3' in po_contents)
+            self.assertFalse('ignored i18n comment #3' in po_contents)
+            self.assertMsgId('Translatable literal #9d', po_contents)
+
+            self.assertFalse('ignored comment #4' in po_contents)
+            self.assertMsgId('Translatable literal #9e', po_contents)
+            self.assertFalse('ignored comment #5' in po_contents)
+
+            self.assertFalse('ignored i18n comment #4' in po_contents)
+            self.assertMsgId('Translatable literal #9f', po_contents)
+            self.assertTrue('#. Translators: valid i18n comment #5' in po_contents)
+
+            self.assertMsgId('Translatable literal #9g', po_contents)
+            self.assertTrue('#. Translators: valid i18n comment #6' in po_contents)
+            self.assertMsgId('Translatable literal #9h', po_contents)
+            self.assertTrue('#. Translators: valid i18n comment #7' in po_contents)
+            self.assertMsgId('Translatable literal #9i', po_contents)
+
+            six.assertRegex(self, po_contents, r'#\..+Translators: valid i18n comment #8')
+            six.assertRegex(self, po_contents, r'#\..+Translators: valid i18n comment #9')
+            self.assertMsgId("Translatable literal #9j", po_contents)
+
 
 class JavascriptExtractorTests(ExtractorTests):
 

tests/regressiontests/i18n/commands/templates/comments.thtml

@@ -0,0 +1,13 @@
+{% load i18n %}
+
+{# ignored comment #1 #}{% trans "Translatable literal #9a" %}
+{# Translators: ignored i18n comment #1 #}{% trans "Translatable literal #9b" %}
+{# Translators: ignored i18n comment #2 #}{# ignored comment #2 #}{% trans "Translatable literal #9c" %}
+{# ignored comment #3 #}{# Translators: ignored i18n comment #3 #}{% trans "Translatable literal #9d" %}
+{# ignored comment #4 #}{% trans "Translatable literal #9e" %}{# ignored comment #5 #}
+{# Translators: ignored i18n comment #4 #}{% trans "Translatable literal #9f" %}{# Translators: valid i18n comment #5 #}
+{% trans "Translatable literal #9g" %}{# Translators: valid i18n comment #6 #}
+{# ignored comment #6 #}{% trans "Translatable literal #9h" %}{# Translators: valid i18n comment #7 #}
+{% trans "Translatable literal #9i" %}
+{# Translators: valid i18n comment #8 #}{# Translators: valid i18n comment #9 #}
+{% trans "Translatable literal #9j" %}