Implement inspect.signature() for sqlite3 connection object

[serhiy-storchaka]

Feature or enhancement

sqlite3.connection() returns a custom callable object. But inspect.signature() returns a generic <Signature (*args, **kwargs)> for it:

>>> import inspect, sqlite3
>>> con = sqlite3.connect(':memory:')
>>> con('select 1')
<sqlite3.Statement object at 0x7f76842d2fd0>
>>> inspect.signature(con)
<Signature (*args, **kwargs)>

This issue is similar to #118285 and #118402.

Linked PRs

• gh-118406: Add signature for sqlite3.Connection objects #118428

[erlend-aasland]

This is interesting. At first, I thought a simple patch a la this could fix it:

diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
index 74984ca536..f49bcd0b49 100644
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -2561,6 +2561,13 @@ set_autocommit(pysqlite_Connection *self, PyObject *val, void *Py_UNUSED(ctx))
     return 0;
 }
 
+#include "clinic/_sqlite3.connect.c.h"
+static PyObject *
+get_sig(pysqlite_Connection *self, void *Py_UNUSED(ctx))
+{
+    return PyUnicode_FromString(pysqlite_connect__doc__);
+}
+
 
 static const char connection_doc[] =
 PyDoc_STR("SQLite database connection object.");
@@ -2570,6 +2577,7 @@ static PyGetSetDef connection_getset[] = {
     {"total_changes",  (getter)pysqlite_connection_get_total_changes, (setter)0},
     {"in_transaction",  (getter)pysqlite_connection_get_in_transaction, (setter)0},
     {"autocommit",  (getter)get_autocommit, (setter)set_autocommit},
+    {"__text_signature__", (getter)get_sig, (setter)0},
     {NULL}
 };
 

However, inspect.signature() will not accept that whole docstring. Manually spelling out only the signature part does not work either. Do you have a solution in hand?

[serhiy-storchaka]

Simply return "(sql)" (or "(sql, /)"?).

I have not solved this simple issue only because it needs tests, and searching in which of many of test_sqlite3 files is more suitable takes time.

[serhiy-storchaka]

See also #118427 for example.

[erlend-aasland]

Ah, I used the incorrect signature. I'll propose a PR soon.