add example for erroneous TypeScript types when using non-"count" agg…

…regate functions

test/aggregate_function.test-d.ts

@@ -0,0 +1,45 @@
+import { expectType } from 'tsd'
+import { PostgrestClient } from '../src/index'
+import { Database } from './types'
+
+const REST_URL = 'http://localhost:3000'
+const postgrest = new PostgrestClient<Database>(REST_URL)
+
+// query for field of top-level resource => succeeds
+{
+  const { data, error } = await postgrest.from('messages').select('numeric_value').single()
+  if (error) throw new Error(error.message)
+  expectType<{ numeric_value: number }>(data)
+}
+
+// `sum` on top-level resource => fails
+{
+  // => const data: SelectQueryError<"Referencing missing column `sum`"> | null
+  const { data, error } = await postgrest.from('messages').select('numeric_value.sum()').single()
+  if (error) throw new Error(error.message)
+  expectType<{ sum: number }>(data)
+}
+
+// `min` and `max` on top-level resource => fails
+{
+  // => const data: SelectQueryError<"Referencing missing column `max`"> | null
+  const { data, error } = await postgrest
+    .from('messages')
+    .select('numeric_value.min(), numeric_value.max()')
+    .single()
+  if (error) throw new Error(error.message)
+  expectType<{ min: number; max: number }>(data)
+}
+
+// `sum` on embedded resource => fails
+{
+  // => users: SelectQueryError<"Referencing missing column `sum`"> | null
+  const { data, error } = await postgrest
+    .from('messages')
+    .select('message, users(numeric_value.sum())')
+    .single()
+  if (error) {
+    throw new Error(error.message)
+  }
+  expectType<{ message: string | null; users: { sum: number } | null }>(data)
+}

test/types.ts

@@ -93,6 +93,7 @@ export interface Database {
           id: number
           message: string | null
           username: string
+          numeric_value: number
         }
         Insert: {
           channel_id: number
@@ -160,6 +161,7 @@ export interface Database {
           data: Json | null
           status: Database['public']['Enums']['user_status'] | null
           username: string
+          numeric_value: number
         }
         Insert: {
           age_range?: unknown | null