sql-kysely: Proxy invariant error on frozen Kysely insert-value nodes

[Ethan826]

Description

The recursive Proxy wrapper in @effect/sql-kysely's effectifyWith (in packages/sql-kysely/src/internal/patch.ts) violates the JS Proxy invariant when it wraps properties of frozen objects created by Kysely's internal AST node constructors.

Error

TypeError: Proxy handler's 'get' result of a non-configurable and non-writable property should be the same value as the target's property
    at get (patch.js:33)
    at compileList (default-query-compiler.js:136)
    at visitValues (default-query-compiler.js:223)
    at visitNode (operation-node-visitor.js:109)
    at visitInsertQuery (default-query-compiler.js:195)
    at visitNode (operation-node-visitor.js:109)
    at compileQuery (default-query-compiler.js:24)
    at <anonymous> (patch.js:49)

Root cause

Two mechanisms conflict:

1. Kysely freezes its AST nodes via Object.freeze() (e.g., ValuesNode.create returns freeze({ kind: 'ValuesNode', values: freeze(values) })). This makes properties non-configurable and non-writable.

2. effectifyWith wraps every non-function property recursively (line 39 of patch.ts):

   return effectifyWith(target[prop], commit, whitelist);

   This creates a new Proxy each time, but the JS spec requires that a Proxy's get trap must return the identical value for non-configurable, non-writable properties.

Reproduction

function effectifyWith(obj) {
  if (typeof obj !== "object" || obj === null) return obj;
  return new Proxy(obj, {
    get(target, prop) {
      if (typeof target[prop] === "function") {
        return (...args) => effectifyWith(target[prop].call(target, ...args));
      }
      return effectifyWith(target[prop]); // violates invariant on frozen props
    },
  });
}

const frozen = Object.freeze({ kind: "ValuesNode", values: Object.freeze([1]) });
const proxied = effectifyWith(frozen);
proxied.values; // throws TypeError

Trigger in practice

A multi-row insertInto().values([...]) where Kysely's ValuesNode.create freezes the values array. During .compile(), the query compiler traverses the AST and accesses frozen properties through the Proxy, triggering the invariant error.

Suggested fix

Add a descriptor check in the get trap to return frozen properties as-is:

get(target, prop) {
  const desc = Object.getOwnPropertyDescriptor(target, prop);
  if (desc && !desc.configurable && !desc.writable) {
    return target[prop]; // must return original value per Proxy invariant
  }
  // ... existing effectify logic
}

Alternatively, check Object.isFrozen(target) and skip wrapping entirely for frozen objects, since they are internal AST nodes that should never be effectified.

Environment

• @effect/sql-kysely: 0.45.0
• kysely: 0.28.11
• Runtime: Bun 1.3.6

Related

• From Discord: Resolving Kysely Integration Issues in Effect with SqlResolver #3299 -- added compile to the method whitelist, which fixed a different manifestation of the same underlying Proxy issue, but did not address frozen non-function properties.