Nullable value is emitted as string "null" but types expect real null

[LestevMisha]

What happened?

Runtime ACT stores an explicit NULL (see value):

{"type":"null","value":"null"}

But the public type declaration says it must be real null (types.d.ts:358):

type LiteralNull = { type: "null"; value: null };

This mismatch creates a TypeScript break:

This comparison appears to be unintentional because the types '"not null" | null | undefined' and '"null"' have no overlap.ts(2367)

Here's minimal repro:

import Parser  from "node-sql-parser";

const sql   = 'CREATE TABLE t (c INT NULL);';
const ast   = new Parser.Parser().astify(sql) as any;
console.log(JSON.stringify(ast[0].create_definitions[0].nullable));
// => { type: 'null', value: 'null' }

Where it stems

In every dialect grammar (pegks/**/*):

// pegjs/mysql.pegjs:876 is used
column_definition_opt
  = n:(literal_not_null / literal_null) {
    if (n && !n.value) n.value = 'null' // <- sentinel string
    return { nullable: n }

Proposals

The short term fix would be:

- type LiteralNull = { type: "null"; value: null };
+ type LiteralNull = { type: "null"; value: null | "null" };

The long term fix is to teach the printer to emit NULL keeping the real null instead of 'null' (that we currently have).

"node-sql-parser": "^5.3.10"
"typescript": "^5.8.3"
node v24.1.0