uesleilima opened a new issue, #2367:
URL: https://github.com/apache/age/issues/2367
**Describe the bug**
The ANTLR4-based `parseAgeValue()` function in `builder.py` crashes with
`AttributeError: 'NoneType' object has no attribute 'stop'` when deserializing
certain vertex records whose properties contain large arrays, long text fields
with special characters, or deeply nested structures.
The crash originates in the ANTLR4 visitor (`ResultVisitor`) when the parser
tree contains `None` nodes that the visitor does not guard against. This makes
the driver unable to parse valid agtype values returned by the AGE engine.
**How are you accessing AGE?**
Python driver (psycopg3)
**Steps to Reproduce**
```python
import age
import psycopg
conn = psycopg.connect("host=localhost port=5432 dbname=postgres
user=postgres password=postgres",
cursor_factory=age.age.ClientCursor)
age.setUpAge(conn, "test_graph")
# Create a vertex with a large tags array and a description with special
characters
with conn.cursor() as cur:
cur.execute("""
SELECT * FROM cypher('test_graph', $$
CREATE (n:TestNode {
name: 'test',
tags: ['tag1', 'tag2', 'tag3', 'tag4', 'tag5', 'tag6',
'tag7',
'tag8', 'tag9', 'tag10', 'tag11', 'tag12'],
description: 'A long description with special chars:
\"quotes\", backslashes \\, newlines, and unicode: àéîõü — em-dash, ellipsis…'
})
RETURN n
$$) AS (n agtype)
""")
conn.commit()
# Now try to read it back through the driver's ANTLR parser
cursor = age.execCypher(conn, "test_graph",
"MATCH (n:TestNode) WHERE n.name = 'test' RETURN n",
cols=["n"])
for row in cursor: # <-- crashes here
print(row)
```
**Expected behavior**
The vertex should be parsed and returned as a `Vertex` object without errors.
**Actual behavior**
```
AttributeError: 'NoneType' object has no attribute 'stop'
```
The traceback points to the ANTLR4 visitor/parser internals. The exact
property combination that triggers the crash varies, but large arrays and
strings with escaped characters are common triggers.
**Current workaround**
We catch exceptions during cursor iteration and fall back to raw SQL
execution via `ag_catalog.cypher(...)` with `::text` casts on every column.
This bypasses the `AgeLoader` → ANTLR4 `parseAgeValue()` path entirely and
returns plain strings that we parse manually with `json.loads()` after
stripping `::vertex`, `::edge`, and `::path` suffixes:
```python
# Fallback: bypass ANTLR4 parser entirely
col_defs = ", ".join(f"{c} agtype" for c in cols)
text_casts = ", ".join(f"{c}::text" for c in cols)
sql = f"SELECT {text_casts} FROM ag_catalog.cypher('{graph}', $$ {cypher}
$$) AS ({col_defs})"
with conn.cursor() as cur:
cur.execute(sql)
for row in cur.fetchall():
# Manual parsing: strip "::vertex" suffix and json.loads()
cleaned = re.sub(r"::(vertex|edge|path)$", "", str(row[0]))
parsed = json.loads(cleaned)
```
**Suggested fix**
Add null-guards in `ResultVisitor` methods (e.g., `visitPair`,
`visitAgValue`, `visitStringValue`) to handle cases where the ANTLR4 parser
tree contains `None` child nodes. Alternatively, regenerate the parser with a
newer ANTLR4 version (>= 4.13.x) which may handle edge cases in the grammar
more robustly.
**Environment**
- Apache AGE: 1.5.0 and 1.6.0
- Python driver: master branch (psycopg3 version, rev `5f5b744`)
- antlr4-python3-runtime: 4.11.1 (also reproduced with 4.13.2)
- psycopg: 3.2.x
- Python: 3.13
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