fix: fixes schema extraction with nested union refs

This was seen in a schema produced by automated tooling. The recursion
guard was too strict in this case as the two occurrences of a
reference ending up having the same guard path name and extraction
would therefore abort before looking inside the second one, instead
returning `{}` which would fail when attempting to inspect the name
field a little lower down.

packages/sanity/src/_internal/cli/actions/graphql/extractFromSanitySchema.ts

@@ -481,7 +481,9 @@ export function extractFromSanitySchema(
     }
 
     try {
-      unionRecursionGuards.add(guardPathName)
+      if (guardPathName !== 'reference') {
+        unionRecursionGuards.add(guardPathName)
+      }
 
       candidates.forEach((def, i) => {
         if (typeNeedsHoisting(def)) {

packages/sanity/test/cli/graphql/extract.test.ts

@@ -4,6 +4,7 @@ import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest'
 import {extractFromSanitySchema} from '../../../src/_internal/cli/actions/graphql/extractFromSanitySchema'
 import {type ApiSpecification} from '../../../src/_internal/cli/actions/graphql/types'
 import testStudioSchema from './fixtures/test-studio'
+import unionRefsSchema from './fixtures/union-refs'
 
 describe('GraphQL - Schema extraction', () => {
   beforeEach(() => {
@@ -15,13 +16,21 @@ describe('GraphQL - Schema extraction', () => {
     vi.runAllTimers()
   })
 
-  it('Should be able to extract schema', () => {
+  it('Should be able to extract schema 1', () => {
     const extracted = extractFromSanitySchema(testStudioSchema, {
       nonNullDocumentFields: false,
     })
 
     expect(sortExtracted(extracted)).toMatchSnapshot()
   })
+
+  it('Should be able to extract schema 2', () => {
+    const extracted = extractFromSanitySchema(unionRefsSchema, {
+      nonNullDocumentFields: false,
+    })
+
+    expect(sortExtracted(extracted)).toMatchSnapshot()
+  })
 })
 
 function sortExtracted(schema: ApiSpecification) {