fix(staging): recognize transfers after nested SQL comments

Signed-off-by: Aakash Saravanan <aakash.saravanan@databricks.com>

Author: aakash-saravanan-db

src/databricks/sql/backend/kernel/client.py

@@ -97,9 +97,15 @@ def _strip_leading_sql_comments(sql: str) -> str:
             nl = sql.find("\n", i)
             i = n if nl == -1 else nl + 1
         elif sql.startswith("/*", i):
-            # Block comment: skip to closing */ (or end if unterminated).
-            close = sql.find("*/", i + 2)
-            i = n if close == -1 else close + 2
+            depth = 1
+            i += 2
+            for delimiter in re.finditer(r"/\*|\*/", sql[i:]):
+                depth += 1 if delimiter.group() == "/*" else -1
+                if depth == 0:
+                    i += delimiter.end()
+                    break
+            else:
+                i = n
         else:
             break
     return sql[i:]

tests/unit/test_kernel_client.py

@@ -822,6 +822,10 @@ def test_execute_command_forwards_row_limit(row_limit):
         ("PUT '/tmp/files/input' INTO '/Volumes/c/s/v/input'", True),
         ("GET '/Volumes/c/s/v/input' TO '/tmp/files/output'", True),
         ("/* download */ GET '/Volumes/c/s/v/input' TO '/tmp/files/output'", True),
+        (
+            "/* outer /* inner */ outer */ GET '/Volumes/c/s/v/input' TO '/tmp/files/output'",
+            True,
+        ),
         ("REMOVE '/Volumes/c/s/v/input'", False),
         ("SELECT 1", False),
     ],
@@ -918,6 +922,9 @@ def execute():
         ("-- upload the file\nPUT '/f' INTO '/v'", "PUT"),
         ("/* staging */ PUT '/f' INTO '/v'", "PUT"),
         ("/* c1 */\n  -- c2\n  get '/v' to '/f'", "GET"),
+        ("/* outer /* inner */ outer */ PUT '/f' INTO '/v'", "PUT"),
+        ("/* a /* b /* c */ b */ a */ GET '/v' TO '/f'", "GET"),
+        ("/* outer /* closed */ PUT '/f' INTO '/v'", None),
         ("   \n\t PUT '/f' INTO '/v'", "PUT"),
         ("SELECT 'GET' AS x", None),
         ("SELECT * FROM puts", None),
@@ -944,6 +951,7 @@ def test_staging_verb_matches_only_the_leading_statement(operation, expected):
         "PUT '__input_stream__'INTO '/Volumes/c/s/v/file'",
         'PUT"__input_stream__"INTO "/Volumes/c/s/v/file"',
         "/* upload */ PUT '__input_stream__' INTO '/Volumes/c/s/v/file'",
+        "/* outer /* inner */ outer */ PUT '__input_stream__' INTO '/Volumes/c/s/v/file'",
         "PUT'__input_stream__' INTO '/Volumes/c/s/v/file'",
         "/* upload */ PUT\"__input_stream__\" INTO '/Volumes/c/s/v/file'",
     ],