fix(postgrest): URL replacement logic in query builder

infra/postgrest/db/00-schema.sql

@@ -111,3 +111,15 @@ CREATE TABLE public.addresses (
   username text REFERENCES users NOT NULL,
   location geometry(POINT,4326)
 );
+
+-- Test Table For UPSERT & onConflict
+CREATE TABLE public.imported_data (
+  id bigint GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
+  external_id text NOT NULL,
+  source_system text NOT NULL,
+  data jsonb DEFAULT null,
+  status text DEFAULT 'pending',
+  created_at timestamp with time zone default timezone('utc'::text, now()) not null,
+  updated_at timestamp with time zone default timezone('utc'::text, now()) not null,
+  UNIQUE(external_id, source_system)
+);

packages/postgrest/lib/src/postgrest_query_builder.dart

@@ -153,20 +153,22 @@ class PostgrestQueryBuilder<T> extends RawPostgrestBuilder<T, T, T> {
     if (!defaultToNull) {
       newHeaders['Prefer'] = '${newHeaders['Prefer']!},missing=default';
     }
+
     Uri url = _url;
+
+    if (values is List) {
+      url = _setColumnsSearchParam(values);
+    }
+
     if (onConflict != null) {
-      url = _url.replace(
+      url = url.replace(
         queryParameters: {
           'on_conflict': onConflict,
-          ..._url.queryParameters,
+          ...url.queryParameters,
         },
       );
     }
 
-    if (values is List) {
-      url = _setColumnsSearchParam(values);
-    }
-
     return PostgrestFilterBuilder<T>(_copyWith(
       method: METHOD_POST,
       headers: newHeaders,

packages/postgrest/test/upsert_test.dart

@@ -0,0 +1,176 @@
+import 'package:postgrest/postgrest.dart';
+import 'package:test/test.dart';
+
+import 'reset_helper.dart';
+
+void main() {
+  const rootUrl = 'http://localhost:3000';
+  late PostgrestClient postgrest;
+  final resetHelper = ResetHelper();
+
+  group('UPSERT & onConflict tests', () {
+    setUpAll(() async {
+      postgrest = PostgrestClient(rootUrl);
+      await resetHelper.initialize(postgrest);
+    });
+
+    setUp(() {
+      postgrest = PostgrestClient(rootUrl);
+    });
+
+    tearDown(() async {
+      await resetHelper.reset();
+    });
+
+    test('upsert with List values and onConflict parameter', () async {
+      // Clean up the imported_data table before starting the test
+      await postgrest.from('imported_data').delete().neq('id', 0);
+
+      // Test data - 3 rows with unique constraint on external_id + source_system
+      final testData = [
+        {
+          'external_id': 'ext_001',
+          'source_system': 'system_a',
+          'data': {'name': 'Test Item 1', 'value': 100},
+          'status': 'active'
+        },
+        {
+          'external_id': 'ext_002',
+          'source_system': 'system_a',
+          'data': {'name': 'Test Item 2', 'value': 200},
+          'status': 'active'
+        },
+        {
+          'external_id': 'ext_003',
+          'source_system': 'system_b',
+          'data': {'name': 'Test Item 3', 'value': 300},
+          'status': 'active'
+        }
+      ];
+
+      // Step 1: INSERT 3 rows (without onConflict)
+      final insertResult =
+          await postgrest.from('imported_data').insert(testData).select();
+
+      expect(insertResult.length, 3);
+      expect(insertResult[0]['external_id'], 'ext_001');
+      expect(insertResult[1]['external_id'], 'ext_002');
+      expect(insertResult[2]['external_id'], 'ext_003');
+
+      // Step 2: UPSERT with first row from test data (without onConflict) - should fail
+      final duplicateData = [
+        {
+          'external_id': 'ext_001',
+          'source_system': 'system_a',
+          'data': {'name': 'Updated Item 1', 'value': 150},
+          'status': 'updated'
+        }
+      ];
+
+      try {
+        await postgrest.from('imported_data').upsert(duplicateData).select();
+        fail(
+            'Expected upsert without onConflict to fail due to unique constraint violation');
+      } on PostgrestException catch (error) {
+        // Should fail with unique constraint violation
+        expect(error.code, '23505'); // PostgreSQL unique violation error code
+      }
+
+      // Step 3: UPSERT with first row from test data (with onConflict) - should succeed
+      final updatedData = [
+        {
+          'external_id': 'ext_001',
+          'source_system': 'system_a',
+          'data': {'name': 'Successfully Updated Item 1', 'value': 175},
+          'status': 'updated_via_upsert'
+        }
+      ];
+
+      final upsertResult = await postgrest
+          .from('imported_data')
+          .upsert(
+            updatedData,
+            onConflict: 'external_id,source_system',
+          )
+          .select();
+
+      expect(upsertResult.length, 1);
+      expect(upsertResult[0]['external_id'], 'ext_001');
+      expect(upsertResult[0]['source_system'], 'system_a');
+      expect(upsertResult[0]['status'], 'updated_via_upsert');
+      expect(upsertResult[0]['data']['name'], 'Successfully Updated Item 1');
+      expect(upsertResult[0]['data']['value'], 175);
+
+      // Step 4: GET to confirm the UPSERT updated the row
+      final verifyResult = await postgrest
+          .from('imported_data')
+          .select()
+          .eq('external_id', 'ext_001')
+          .eq('source_system', 'system_a');
+
+      expect(verifyResult.length, 1);
+      expect(verifyResult[0]['status'], 'updated_via_upsert');
+      expect(verifyResult[0]['data']['name'], 'Successfully Updated Item 1');
+      expect(verifyResult[0]['data']['value'], 175);
+
+      // Verify total count is still 3 (no new rows added, just updated)
+      final allRows = await postgrest.from('imported_data').select();
+      expect(allRows.length, 3);
+    });
+
+    test('upsert with List values and onConflict - multiple rows update',
+        () async {
+      // Clean up the imported_data table before starting the test
+      await postgrest.from('imported_data').delete().neq('id', 0);
+
+      // Test the fix with multiple rows in a single upsert operation
+      final initialData = [
+        {
+          'external_id': 'batch_001',
+          'source_system': 'batch_system',
+          'data': {'batch': 1, 'initial': true},
+          'status': 'initial'
+        },
+        {
+          'external_id': 'batch_002',
+          'source_system': 'batch_system',
+          'data': {'batch': 1, 'initial': true},
+          'status': 'initial'
+        }
+      ];
+
+      // Insert initial data
+      await postgrest.from('imported_data').insert(initialData).select();
+
+      // Update both rows in a single upsert operation
+      final updateData = [
+        {
+          'external_id': 'batch_001',
+          'source_system': 'batch_system',
+          'data': {'batch': 1, 'updated': true},
+          'status': 'batch_updated'
+        },
+        {
+          'external_id': 'batch_002',
+          'source_system': 'batch_system',
+          'data': {'batch': 1, 'updated': true},
+          'status': 'batch_updated'
+        }
+      ];
+
+      final batchUpsertResult = await postgrest
+          .from('imported_data')
+          .upsert(
+            updateData,
+            onConflict: 'external_id,source_system',
+          )
+          .select();
+
+      expect(batchUpsertResult.length, 2);
+      expect(batchUpsertResult[0]['status'], 'batch_updated');
+      expect(batchUpsertResult[1]['status'], 'batch_updated');
+      expect(batchUpsertResult[0]['data']['updated'], true);
+      expect(batchUpsertResult[1]['data']['updated'], true);
+    });
+  });
+}