Empty JSON array binds as ARRAY[] instead of '{}' (server errors in many array-column contexts)

[aesslinger]

Summary

json_array_to_pg_literal has no empty-array special case. An empty JSON array [] produces ARRAY[] (an ARRAY[] constructor with no elements), where the built-in driver returns {} — the canonical PostgreSQL empty-array literal that the server always accepts. ARRAY[] is accepted only when the target column type is unambiguous; in many contexts it is a syntax/type error.

Builtin behavior (upstream main)

src-tauri/src/drivers/postgres/helpers.rs::json_array_to_pg_literal:

pub fn json_array_to_pg_literal(arr: &[serde_json::Value]) -> Result<String, String> {
    if arr.is_empty() {
        return Ok("{}".to_string());
    }
    // … ARRAY[...] for non-empty
}

Plugin behavior (this repo)

src/binding.rs:333 — json_array_to_pg_literal has no is_empty() guard. An empty [] skips the loop (parts stays empty) and returns format!("ARRAY[{}]", "") = ARRAY[]. The non-empty path matches the builtin exactly (ARRAY[...]); only the empty case diverges.

This is reached both from the Value::Array arm in bind_pg_value (src/binding.rs:106) and the inline array-literal parse in bind_pg_string (:287).

Reproduction

CREATE TABLE t (ids int[]);

Inserting {"ids": []}:

• Builtin: INSERT INTO "s"."t" (ids) VALUES ({}) → succeeds.
• Plugin: INSERT INTO "s"."t" (ids) VALUES (ARRAY[]) → syntax error at or near "]" / cannot determine type of empty array depending on context.

Impact

• Severity: Medium. INSERT/UPDATE of an empty array into an array column fails server-side where the builtin succeeds. The error message is a generic syntax/type error, not clearly tied to the empty array.
• Not caught by the parity suite (no empty-array bind test).

Fix

Add the empty-array guard at the top of json_array_to_pg_literal (src/binding.rs:333):

if arr.is_empty() {
    return Ok("{}".to_string());
}

Add a unit test in binding_tests.rs: a Value::Array(vec![]) binds to {}, not ARRAY[].

Related

• Builtin reference: TabularisDB/tabularis drivers/postgres/helpers.rs::json_array_to_pg_literal.