fix(json): handle BLOB arguments correctly in JSON functions

[nunogoncalves03]

Description

This PR updates JSON functions to correctly reject BLOB values, aligning their behavior with SQLite. It also fixes handling of text-based JSON passed as BLOB arguments to json(), which previously did not work as expected.

Previously, JSON functions (json_object, json_set, json_insert, json_replace, and their jsonb variants) attempted to convert BLOB values into JSON instead of rejecting them with an error. This differed from SQLite's behavior, which returns the error JSON cannot hold BLOB values. In addition, these functions were silently converting errors to NULL in the executor rather than propagating them to the user.

Additionally, json() previously returned incorrect results when given BLOBs containing JSON text. The root cause was that the function assumed all BLOBs were in binary JSONB format and attempted to parse them as such, leading to incorrect results when the BLOB actually contained textual JSON.

With these changes applied, JSON functions are matching SQLite's behavior:

turso> CREATE TABLE t(a);
turso> INSERT INTO t VALUES (x'74727565'); -- ASCII "true”;
turso> SELECT json_object('a', a) FROM t;
  × Runtime error: JSON cannot hold BLOB values

turso> SELECT json_array(a) FROM t;
  × Runtime error: JSON cannot hold BLOB values

turso> SELECT json_set('{"x":1}', '$.a', a) FROM t;
  × Runtime error: JSON cannot hold BLOB values

turso> SELECT json_insert('{"x":1}', '$.a', a) FROM t;
  × Runtime error: JSON cannot hold BLOB values

turso> SELECT json_replace('{"a":1}', '$.a', a) FROM t;
  × Runtime error: JSON cannot hold BLOB values

turso> SELECT json_quote(a) FROM t;
  × Runtime error: JSON cannot hold BLOB values
turso> SELECT json(x'2268656c6c6f22'); -- ASCII "\"hello\"”;
┌──────────────────────────┐
│ json (X'2268656c6c6f22') │
├──────────────────────────┤
│ "hello"                  │
└──────────────────────────┘

Motivation and context

This PR fixes the issues identified in #4195 to align with SQLite’s behavior.

Currently, Turso handles BLOB inputs inconsistently across JSON functions:

turso> CREATE TABLE t(a);
turso> INSERT INTO t VALUES (x'74727565'); -- ASCII "true”;
turso> SELECT json_object('a', a) FROM t;
┌────────────────────────┐
│ json_object ('a', t.a) │
├────────────────────────┤
│ {"a":true}             │
└────────────────────────┘
turso> SELECT json_array(a) FROM t;
  × Runtime error: JSON cannot hold BLOB values

turso> SELECT json_set('{"x":1}', '$.a', a) FROM t;
┌──────────────────────────────────┐
│ json_set ('{"x":1}', '$.a', t.a) │
├──────────────────────────────────┤
│ {"x":1,"a":true}                 │
└──────────────────────────────────┘
turso> SELECT json_insert('{"x":1}', '$.a', a) FROM t;
┌─────────────────────────────────────┐
│ json_insert ('{"x":1}', '$.a', t.a) │
├─────────────────────────────────────┤
│ {"x":1,"a":true}                    │
└─────────────────────────────────────┘
turso> SELECT json_replace('{"a":1}', '$.a', a) FROM t;
┌──────────────────────────────────────┐
│ json_replace ('{"a":1}', '$.a', t.a) │
├──────────────────────────────────────┤
│ {"a":true}                           │
└──────────────────────────────────────┘
turso> SELECT json_quote(a) FROM t;
  × Runtime error: JSON cannot hold BLOB values
turso> SELECT json(x'2268656c6c6f22'); -- ASCII "\"hello\"”;
┌──────────────────────────┐
│ json (X'2268656c6c6f22') │
├──────────────────────────┤
│ false                    │
└──────────────────────────┘

Expected behavior:

sqlite> CREATE TABLE t(a);
sqlite> INSERT INTO t VALUES (x'74727565'); -- ASCII "true”;
sqlite> SELECT json_object('a', a) FROM t;
Runtime error: JSON cannot hold BLOB values
sqlite> SELECT json_array(a) FROM t;
Runtime error: JSON cannot hold BLOB values
sqlite> SELECT json_set('{"x":1}', '$.a', a) FROM t;
Runtime error: JSON cannot hold BLOB values
sqlite> SELECT json_insert('{"x":1}', '$.a', a) FROM t;
Runtime error: JSON cannot hold BLOB values
sqlite> SELECT json_replace('{"a":1}', '$.a', a) FROM t;
Runtime error: JSON cannot hold BLOB values
sqlite> SELECT json_quote(a) FROM t;
Runtime error: JSON cannot hold BLOB values
sqlite> SELECT json(x'2268656c6c6f22'); -- ASCII "\"hello\"”;
"hello"

Fixes #4195.

AI Disclosure

This PR was developed with assistance from GitHub Copilot (Claude Sonnet 4.5). The AI helped identify the root cause and assisted in writing the tests.

[turso-bot]

Please review @pedrocarlo

[nunogoncalves03]

Messed up the rebase, fixing it now 🙃

Edit: Done!

[pedrocarlo]

@jussisaurio or @PThorpe92 need someone to approve the workflow here to run the test

[nunogoncalves03]

Fixed the failing clippy job, could we rerun the pipeline?

[Pavan-Nambi]

could u please add more tests? specifically like using jsonb? are we supposed to reject them too?

json_funcs(jsonb())

[nunogoncalves03]

You are absolutely right, thanks for catching that! I have pushed a commit adding more tests for the jsonb functions and for json/jsonb interop. Let me know if these tests cover what you were expecting.

Also, while adding these tests, I discovered a bug: Turso wasn’t unescaping strings when converting jsonb to db/sql values, whereas SQLite does.