TypeScript disallows interpolation helper for nested arrays that include null values

[jxddk]

While attempting to perform multiple updates in one query, I encountered what I believe to be a TypeScript issue with the interpolation helper for nested arrays, when the lowest-level arrays include null values. My aim is to update multiple rows (including some values that may be null) in a single query, but the TypeScript error described below prevents me from doing so.

Please see the following TypeScript snippet, which I have run on Deno v1.35.2, using the v3.4.3 version of porsager/postgres. The final code block exemplifies the issue.

import postgres from 'npm:postgres@3.4.3'
const sql = postgres({})

// Calling helper function with an array of integers
console.log(await sql`SELECT * FROM (VALUES ${sql([1, 2, 3, 4])}) AS v(a, b, c, d)`)
// Result(1) [ { a: "1", b: "2", c: "3", d: "4" } ]

// Calling helper function with an array of arrays of integers
console.log(await sql`SELECT * FROM (VALUES ${sql([[1, 2, 3, 4]])}) AS v(a, b, c, d)`)
// Result(1) [ { a: "1", b: "2", c: "3", d: "4" } ]

// Calling helper function with an array including a null value
console.log(await sql`SELECT * FROM (VALUES ${sql([1, 2, null, 4])}) AS v(a, b, c, d)`)
// Result(1) [ { a: "1", b: "2", c: null, d: "4" }

// Calling helper function with an array of arrays including a null value
console.log(await sql`SELECT * FROM (VALUES ${sql([[1, 2, null, 4]])}) AS v(a, b, c, d)`)
// TS2769 [ERROR]: No overload matches this call.
// Overload 1 of 2, '(first: (number | null)[][] & readonly EscapableArray[]): Helper<(number | null)[][], []>', gave the following error.
//   Type 'null' is not assignable to type 'number'.  Overload 2 of 2, '(template: TemplateStringsArray, ...parameters: readonly ParameterOrFragment<never>[]): PendingQuery<Row[]>', gave the following error.
//   Type '[number, number, null, number]' is not assignable to type 'string'.

// Calling helper function with an array of arrays of strings
const names_set_a: [string, string, string][] = [
    ['Alicia', 'Beatrice', 'Clydeston'],
    ['Andrew', 'Bob', 'Cornwall'],
    ['Agnes', 'Bentley', 'Clifson'],
]
console.log(sql`
    UPDATE names SET
        middle=n.middle,
    FROM (VALUES ${sql(names_set_a)})
    AS n(
        first,
        middle,
        last,
    )
    WHERE n.first = first AND n.last = last
`)

// Calling helper function with an array of arrays of strings including nulls
const names_set_b: [string, null, string][] = [
    ['Andrew', null, 'Cornwall'],
    ['Alicia', null, 'Clydeston'],
    ['Agnes', null, 'Clifson'],
]
console.log(sql`
    UPDATE names SET
        middle=n.middle,
    FROM (VALUES ${sql(names_set_b)})
    AS n(
        first,
        middle,
        last,
    )
    WHERE n.first = first AND n.last = last
`)
// TS2769 [ERROR]: No overload matches this call.
//   Overload 1 of 2, '(first: [string, null, string][] & readonly EscapableArray[]): Helper<[string, null, string][], []>', gave the following error.
//     Argument of type '[string, null, string][]' is not assignable to parameter of type '[string, null, string][] & readonly EscapableArray[]'.
//       Type '[string, null, string][]' is not assignable to type 'readonly EscapableArray[]'.
//         Type '[string, null, string]' is not assignable to type 'EscapableArray'.
//           Type 'string | null' is not assignable to type 'string | number'.
//             Type 'null' is not assignable to type 'string | number'.  Overload 2 of 2, '(template: TemplateStringsArray, ...parameters: readonly ParameterOrFragment<never>[]): PendingQuery<Row[]>', gave the following error.
//     Argument of type '[string, null, string][]' is not assignable to parameter of type 'TemplateStringsArray'.
//       Property 'raw' is missing in type '[string, null, string][]' but required in type 'TemplateStringsArray'.

I will attempt to diagnose (and if possible, fix) this issue, and am posting this here in case there are any clear pointers, easy fixes, or different approaches that I may have missed. Thanks in advance.

[baileywickham]

We also hit this issue but with a different type, in our case a Buffer.