fix: csv bug and type error

Author: soedirgo

src/lib/PostgrestTransformBuilder.ts

@@ -123,8 +123,8 @@ export default class PostgrestTransformBuilder<T> extends PostgrestBuilder<T> {
   /**
    * Set the response type to CSV.
    */
-  csv(): this {
+  csv(): PromiseLike<PostgrestSingleResponse<string>> {
     this.headers['Accept'] = 'text/csv'
-    return this
+    return this as PromiseLike<PostgrestSingleResponse<string>>
   }
 }

src/lib/types.ts

@@ -104,8 +104,13 @@ export abstract class PostgrestBuilder<T> implements PromiseLike<PostgrestRespon
           const isReturnMinimal = this.headers['Prefer']?.split(',').includes('return=minimal')
           if (this.method !== 'HEAD' && !isReturnMinimal) {
             const text = await res.text()
-            if (text && text !== '' && this.headers['Accept'] !== 'text/csv')
+            if (!text) {
+              // discard `text`
+            } else if (this.headers['Accept'] === 'text/csv') {
+              data = text
+            } else {
               data = JSON.parse(text)
+            }
           }
 
           const countHeader = this.headers['Prefer']?.match(/count=(exact|planned|estimated)/)