`groq-invalid-type-filter` false positive for discriminated union object types in arrays

[nkgentile]

Bug Description

The sanity/groq-invalid-type-filter rule incorrectly flags _type filters on array items (discriminated union members) as invalid document types.

Example

Given a schema with object types used as discriminated unions in arrays:

// Object types (NOT document types)
defineType({
  name: 'textBlock',
  type: 'object',
  fields: [{ name: 'text', type: 'text' }],
})

defineType({
  name: 'imageBlock',
  type: 'object',
  fields: [{ name: 'asset', type: 'image' }],
})

// Document type with polymorphic array
defineType({
  name: 'post',
  type: 'document',
  fields: [
    {
      name: 'content',
      type: 'array',
      of: [{ type: 'textBlock' }, { type: 'imageBlock' }],
    },
  ],
})

This valid GROQ query:

*[_type == "post"] {
  "images": content[_type == "imageBlock"]
}

Produces the error:

Document type "imageBlock" does not exist in schema

Expected Behavior

The rule should distinguish between:

1. Document type filters (top-level *[_type == "..."]) - should be validated against schema document types
2. Array item filters (array[_type == "..."]) - should recognize object types used as discriminated union members

Current Behavior

All _type == "..." filters are validated against document types only, causing false positives for legitimate discriminated union patterns.

Environment

• @sanity/eslint-plugin: 0.3.0
• @sanity/groq-lint: 0.0.3

Workaround

Currently suppressing with eslint-disable comments, but this masks real issues.

[kmelve]

Hey @nkgentile! 👋

I've opened #28 to fix this issue. The fix detects whether a _type comparison is in a top-level document filter (*[...]) vs a nested array filter (field[...]), and only validates against document types for top-level filters.

How to test the fix

You can test the PR before it's merged by installing directly from the branch:

# Using npm
npm install github:sanity-labs/sanity-lint#fix/invalid-type-filter-discriminated-unions

# Using pnpm
pnpm add github:sanity-labs/sanity-lint#fix/invalid-type-filter-discriminated-unions

Or if you want to test locally:

# Clone and build
git clone https://github.com/sanity-labs/sanity-lint.git
cd sanity-lint
git checkout fix/invalid-type-filter-discriminated-unions
pnpm install
pnpm build

# Then link the package to your project
cd packages/groq-lint
pnpm link --global

# In your project
pnpm link --global @sanity-labs/groq-lint

After installing, your query should no longer produce false positives:

*[_type == "post"] { "images": content[_type == "imageBlock"] }

Would love to hear if this resolves the issue for you!