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

sqlparse/filters/others.py

@@ -63,8 +63,20 @@ class StripCommentsFilter:
             ):
                 # Insert a whitespace to ensure the following SQL produces
                 # a valid SQL (see #425).
-                if prev_ is not None and not prev_.match(T.Punctuation, '('):
-                    tlist.tokens.insert(tidx, _get_insert_token(token))
+                insert_tok = _get_insert_token(token)
+                # A plain space separator is redundant when a neighbour is
+                # already whitespace, which happens for comments interleaved
+                # inside a grouped identifier. A line break carried by the
+                # comment is always kept.
+                redundant_space = (
+                    insert_tok.is_whitespace and not insert_tok.is_newline
+                    and ((prev_ is not None and prev_.is_whitespace)
+                         or (next_ is not None and next_.is_whitespace))
+                )
+                if (prev_ is not None
+                        and not prev_.match(T.Punctuation, '(')
+                        and not redundant_space):
+                    tlist.tokens.insert(tidx, insert_tok)
                 tlist.tokens.remove(token)
                 tidx -= 1
             else:

sqlparse/sql.py

@@ -387,7 +387,9 @@ class TokenList(Token):
         A parent object is identified by the first occurring dot.
         """
         dot_idx, _ = self.token_next_by(m=(T.Punctuation, '.'))
-        _, prev_ = self.token_prev(dot_idx)
+        # skip_cm so a comment between the parent name and the dot (issue712)
+        # does not get mistaken for the parent name.
+        _, prev_ = self.token_prev(dot_idx, skip_cm=True)
         return remove_quotes(prev_.value) if prev_ is not None else None
 
     def _get_first_name(self, idx=None, reverse=False, keywords=False,