feat: optimize custom selection set type

[pranavosu]

Problem

Issue number, if available:

#424

Changes

Corresponding docs PR, if applicable: N/A

Validation

Test project: https://github.com/pranavosu/selection-set-repro

prereq: valid AWS creds

test commands: npx ampx sandbox -> npm run build -> npm run start

run without overrides ("@aws-amplify/data-schema": "1.22.0",) and then with the @amplify/data-schema package overrides (0.0.0-optimize-selection-sets-20260108232711).

Checklist

• If this PR includes a functional change to the runtime or type-level behavior of the code, I have added or updated automated test coverage for this change. (see Testing Strategy README)
• If this PR requires a docs update, I have linked to that docs PR above.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3733d95

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@aws-amplify/data-schema	Minor

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[oe-bayram]

We applied these changes as a patch to our project, but we still get the error message from #424

TS2590: Expression produces a union type that is too complex to represent.

[pranavosu]

We applied these changes as a patch to our project, but we still get the error message from #424

TS2590: Expression produces a union type that is too complex to represent.

Are you sure all instances of @amplify/data-schema are updated? You might need to add overrides. I'd think if you want to test this use - "@aws-amplify/data-schema":"0.0.0-optimize-selection-sets-20260108232711" as an override for your project.

[bobbor]

tried my best to understand what is actually going on here.

I left a bunch of comments. If what I wrote makes no sense I would understand that too :D

[oe-bayram]

I’ve installed the snapshot version via npm overrides as suggested.
This resolves the TS2590 error from #424, however it introduces a new issue:

The SelectionSet type no longer resolves correctly and now collapses to any.

import { SelectionSet } from 'aws-amplify/api';

export type User = SelectionSet<
  Schema['User']['type'],
  [
    'id',
    'firstName',
    'lastName',
    'email',
    'workingContracts.*',
    'workingContracts.workingTimeModelID',
  ]
>;

Before applying the snapshot, this produced the expected strongly typed result (but triggered TS2590).
With the optimized version, the compiler error is gone, but User is now inferred as any.

When using the same selection set for querying, the returned data is correctly typed:

const { data } = await client.models.User.list({
  selectionSet: UserSelectionSet,
});

[oe-bayram]

I’ve installed the snapshot version via npm overrides as suggested. This resolves the TS2590 error from #424, however it introduces a new issue:

The SelectionSet type no longer resolves correctly and now collapses to any.

import { SelectionSet } from 'aws-amplify/api';

export type User = SelectionSet<
  Schema['User']['type'],
  [
    'id',
    'firstName',
    'lastName',
    'email',
    'workingContracts.*',
    'workingContracts.workingTimeModelID',
  ]
>;

Before applying the snapshot, this produced the expected strongly typed result (but triggered TS2590). With the optimized version, the compiler error is gone, but User is now inferred as any.

When using the same selection set for querying, the returned data is correctly typed:

const { data } = await client.models.User.list({
  selectionSet: UserSelectionSet,
});

Thanks — I found the reason why my SelectionSet alias was resolving to any.

The first generic parameter of SelectionSet<…> must be the model definition (the thing that includes __meta / flatModel), not the plain model “type” shape. In my case I incorrectly used:

type User = SelectionSet<
  Schema['User']['type'], 
  typeof UserSelectionSet
>

Since Schema['User']['type'] does NOT extend ClientSchemaByEntityTypeBaseShape['models'][string], the conditional type falls back to any.

Switching it to the model definition fixes it:

type User = SelectionSet<
  Schema['User'], 
  typeof UserSelectionSet
>

[pranavosu]

Thanks for the feedback @oe-bayram! Appreciate it.