fix: group dotted identifiers split by interleaved comments (issue712)

Identifiers may carry comments between their tokens (e.g. name -- c\n . -- c\n obj). _group only skipped whitespace when locating the tokens around a joining token, so an interleaved comment defeated the prev/next checks and the identifier was never formed.

Add an opt-in skip_comments flag to _group and enable it for group_period and group_as; the comments stay inside the resulting group. Also skip comments in get_parent_name and avoid a redundant separating space in StripCommentsFilter for the newly reachable interleaved-comment identifiers.

sqlparse/engine/grouping.py

@@ -188,7 +188,8 @@ def group_period(tlist):
 
         return (pidx, nidx) if valid_next else (pidx, tidx)
 
-    _group(tlist, sql.Identifier, match, valid_prev, valid_next, post)
+    _group(tlist, sql.Identifier, match, valid_prev, valid_next, post,
+           skip_comments=True)
 
 
 def group_as(tlist):
@@ -205,7 +206,8 @@ def group_as(tlist):
     def post(tlist, pidx, tidx, nidx):
         return pidx, nidx
 
-    _group(tlist, sql.Identifier, match, valid_prev, valid_next, post)
+    _group(tlist, sql.Identifier, match, valid_prev, valid_next, post,
+           skip_comments=True)
 
 
 def group_assignment(tlist):
@@ -481,9 +483,16 @@ def _group(tlist, cls, match,
            post=None,
            extend=True,
            recurse=True,
-           depth=0
+           depth=0,
+           skip_comments=False
            ):
-    """Groups together tokens that are joined by a middle token. i.e. x < y"""
+    """Groups together tokens that are joined by a middle token. i.e. x < y
+
+    When *skip_comments* is ``True`` comments interleaved between the joined
+    tokens are ignored while looking for the previous and next token, so
+    e.g. ``a -- c\\n . -- c\\n b`` still groups into a single identifier
+    (issue712). The comments themselves stay inside the resulting group.
+    """
     if MAX_GROUPING_DEPTH is not None and depth > MAX_GROUPING_DEPTH:
         raise SQLParseError(
             f"Maximum grouping depth exceeded ({MAX_GROUPING_DEPTH})."
@@ -510,10 +519,10 @@ def _group(tlist, cls, match,
 
         if recurse and token.is_group and not isinstance(token, cls):
             _group(token, cls, match, valid_prev, valid_next,
-                   post, extend, True, depth + 1)
+                   post, extend, True, depth + 1, skip_comments)
 
         if match(token):
-            nidx, next_ = tlist.token_next(tidx)
+            nidx, next_ = tlist.token_next(tidx, skip_cm=skip_comments)
             if prev_ and valid_prev(prev_) and valid_next(next_):
                 from_idx, to_idx = post(tlist, pidx, tidx, nidx)
                 grp = tlist.group_tokens(cls, from_idx, to_idx, extend=extend)
@@ -522,4 +531,9 @@ def _group(tlist, cls, match,
                 pidx, prev_ = from_idx, grp
                 continue
 
+        if skip_comments and imt(token, t=T.Comment, i=sql.Comment):
+            # Keep prev_ pointing at the real previous token so an interleaved
+            # comment does not defeat valid_prev (issue712).
+            continue
+
         pidx, prev_ = tidx, token