fix(flags): avoid Flutter Web intake preflights

packages/datadog_flags/lib/src/evaluation_aggregator.dart

@@ -7,13 +7,12 @@ import 'dart:async';
 import 'dart:convert';
 
 import 'package:meta/meta.dart';
-import 'package:uuid/uuid.dart';
 
 import 'assignment.dart';
 import 'evaluation_context.dart';
 import 'flags_runtime.dart';
+import 'intake_request.dart';
 import 'json_value.dart';
-import 'sdk_metadata.dart';
 
 class EvaluationAggregator {
   static const int defaultMaxBatchSize = 1000;
@@ -172,24 +171,23 @@ class EvaluationAggregator {
     List<_AggregatedEvaluation> evaluations, {
     required bool rescheduleOnFailure,
   }) async {
-    final endpoint = _evaluationEndpoint();
-    final body = jsonEncode({
-      'context': _datadogContext(),
-      'flagEvaluations': evaluations.map((e) => e.toJson()).toList(),
-    });
+    final request = buildFlagsIntakeRequest(
+      endpoint: _evaluationEndpoint(),
+      clientToken: runtime.datadogConfig.clientToken,
+      nativeContentType: 'application/json',
+      nativeBodyBuilder: () => jsonEncode({
+        'context': _datadogContext(),
+        'flagEvaluations': evaluations.map((e) => e.toJson()).toList(),
+      }),
+      webBodyBuilder: () => evaluations.map(_webEvaluationJson).join('\n'),
+    );
 
     try {
       final response = await runtime.httpClient
           .post(
-            endpoint,
-            headers: {
-              'Content-Type': 'application/json',
-              'DD-API-KEY': runtime.datadogConfig.clientToken,
-              'DD-EVP-ORIGIN': datadogFlagsSource,
-              'DD-EVP-ORIGIN-VERSION': datadogFlagsSdkVersion,
-              'DD-REQUEST-ID': const Uuid().v4(),
-            },
-            body: body,
+            request.endpoint,
+            headers: request.headers,
+            body: request.body,
           )
           .timeout(uploadTimeout);
       if (response.statusCode < 200 || response.statusCode >= 300) {
@@ -239,14 +237,22 @@ class EvaluationAggregator {
 
   Uri _evaluationEndpoint() {
     final datadogConfig = runtime.datadogConfig;
-    final endpoint = runtime.configuration.customEvaluationEndpoint ??
+    return runtime.configuration.customEvaluationEndpoint ??
         datadogConfig.intakeEndpoint().replace(path: '/api/v2/flagevaluation');
-    return endpoint.replace(
-      queryParameters: {
-        ...endpoint.queryParameters,
-        'ddsource': datadogFlagsSource,
-      },
-    );
+  }
+
+  String _webEvaluationJson(_AggregatedEvaluation evaluation) {
+    final event = evaluation.toJson();
+    final eventContext = switch (event['context']) {
+      Map<String, Object?> context => Map<String, Object?>.from(context),
+      _ => <String, Object?>{},
+    };
+    final datadogContext = _datadogContext();
+    if (datadogContext.isNotEmpty) {
+      eventContext['dd'] = datadogContext;
+      event['context'] = eventContext;
+    }
+    return jsonEncode(event);
   }
 
   Map<String, Object?> _datadogContext() {

packages/datadog_flags/lib/src/exposure_logger.dart

@@ -7,13 +7,12 @@ import 'dart:async';
 import 'dart:convert';
 
 import 'package:meta/meta.dart';
-import 'package:uuid/uuid.dart';
 
 import 'assignment.dart';
 import 'evaluation_context.dart';
 import 'flags_runtime.dart';
+import 'intake_request.dart';
 import 'json_value.dart';
-import 'sdk_metadata.dart';
 
 class ExposureLogger {
   static const Duration defaultUploadTimeout = Duration(seconds: 15);
@@ -145,18 +144,20 @@ class ExposureLogger {
     List<Map<String, Object?>> exposures, {
     required bool rescheduleOnFailure,
   }) async {
+    final body = exposures.map(jsonEncode).join('\n');
+    final request = buildFlagsIntakeRequest(
+      endpoint: _exposureEndpoint(),
+      clientToken: runtime.datadogConfig.clientToken,
+      nativeContentType: 'text/plain;charset=UTF-8',
+      nativeBodyBuilder: () => body,
+      webBodyBuilder: () => body,
+    );
     try {
       final response = await runtime.httpClient
           .post(
-            _exposureEndpoint(),
-            headers: {
-              'Content-Type': 'text/plain;charset=UTF-8',
-              'DD-API-KEY': runtime.datadogConfig.clientToken,
-              'DD-EVP-ORIGIN': datadogFlagsSource,
-              'DD-EVP-ORIGIN-VERSION': datadogFlagsSdkVersion,
-              'DD-REQUEST-ID': const Uuid().v4(),
-            },
-            body: exposures.map(jsonEncode).join('\n'),
+            request.endpoint,
+            headers: request.headers,
+            body: request.body,
           )
           .timeout(uploadTimeout);
       if (response.statusCode < 200 || response.statusCode >= 300) {
@@ -224,14 +225,8 @@ class ExposureLogger {
 
   Uri _exposureEndpoint() {
     final datadogConfig = runtime.datadogConfig;
-    final endpoint = runtime.configuration.customExposureEndpoint ??
+    return runtime.configuration.customExposureEndpoint ??
         datadogConfig.intakeEndpoint().replace(path: '/api/v2/exposures');
-    return endpoint.replace(
-      queryParameters: {
-        ...endpoint.queryParameters,
-        'ddsource': datadogFlagsSource,
-      },
-    );
   }
 }
 

packages/datadog_flags/lib/src/intake_platform.dart

@@ -0,0 +1,7 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0. This product includes software
+// developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+export 'intake_platform_web.dart'
+    if (dart.library.io) 'intake_platform_native.dart';

packages/datadog_flags/lib/src/intake_platform_native.dart

@@ -0,0 +1,6 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0. This product includes software
+// developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+const isWebFlagsIntake = false;

packages/datadog_flags/lib/src/intake_platform_web.dart

@@ -0,0 +1,6 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0. This product includes software
+// developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+const isWebFlagsIntake = true;

packages/datadog_flags/lib/src/intake_request.dart

@@ -0,0 +1,65 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0. This product includes software
+// developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+import 'package:meta/meta.dart';
+import 'package:uuid/uuid.dart';
+
+import 'intake_platform.dart';
+import 'sdk_metadata.dart';
+
+@immutable
+final class FlagsIntakeRequest {
+  final Uri endpoint;
+  final Map<String, String> headers;
+  final String body;
+
+  const FlagsIntakeRequest({
+    required this.endpoint,
+    required this.headers,
+    required this.body,
+  });
+}
+
+FlagsIntakeRequest buildFlagsIntakeRequest({
+  required Uri endpoint,
+  required String clientToken,
+  required String nativeContentType,
+  required String Function() nativeBodyBuilder,
+  required String Function() webBodyBuilder,
+}) {
+  final requestId = const Uuid().v4();
+  final queryParameters = {
+    ...endpoint.queryParameters,
+    'ddsource': datadogFlagsSource,
+    if (isWebFlagsIntake) ...{
+      'dd-api-key': clientToken,
+      'dd-evp-origin-version': datadogFlagsSdkVersion,
+      'dd-evp-origin': datadogFlagsSource,
+      'dd-request-id': requestId,
+    },
+  };
+
+  if (isWebFlagsIntake) {
+    // Match the Browser SDK transport so the browser does not send an OPTIONS
+    // CORS preflight before each intake request.
+    return FlagsIntakeRequest(
+      endpoint: endpoint.replace(queryParameters: queryParameters),
+      headers: const {'Content-Type': 'text/plain'},
+      body: webBodyBuilder(),
+    );
+  }
+
+  return FlagsIntakeRequest(
+    endpoint: endpoint.replace(queryParameters: queryParameters),
+    headers: {
+      'Content-Type': nativeContentType,
+      'DD-API-KEY': clientToken,
+      'DD-EVP-ORIGIN': datadogFlagsSource,
+      'DD-EVP-ORIGIN-VERSION': datadogFlagsSdkVersion,
+      'DD-REQUEST-ID': requestId,
+    },
+    body: nativeBodyBuilder(),
+  );
+}

packages/datadog_flags/test/datadog_flags_test.dart

@@ -10,6 +10,7 @@ import 'package:datadog_flags/datadog_flags.dart';
 import 'package:datadog_flags/src/evaluation_aggregator.dart';
 import 'package:datadog_flags/src/exposure_logger.dart';
 import 'package:datadog_flags/src/flags_store.dart';
+import 'package:datadog_flags/src/intake_platform.dart';
 import 'package:datadog_flags/src/sdk_metadata.dart';
 import 'package:http/http.dart' as http;
 import 'package:http/testing.dart';
@@ -339,14 +340,13 @@ void main() {
       expect(_exposureRequests(requests), hasLength(1));
       final request = _exposureRequests(requests).single;
       expect(
-        request.url.toString(),
-        'https://browser-intake-datadoghq.com/api/v2/exposures?ddsource=dart-client',
+        '${request.url.origin}${request.url.path}',
+        'https://browser-intake-datadoghq.com/api/v2/exposures',
+      );
+      _expectIntakeMetadata(
+        request,
+        nativeContentType: 'text/plain;charset=UTF-8',
       );
-      expect(request.headers['Content-Type'], 'text/plain;charset=UTF-8');
-      expect(request.headers['DD-API-KEY'], 'client-token');
-      expect(request.headers['DD-EVP-ORIGIN'], 'dart-client');
-      expect(request.headers['DD-EVP-ORIGIN-VERSION'], datadogFlagsSdkVersion);
-      expect(request.headers['DD-REQUEST-ID'], isNotEmpty);
 
       final exposure = _exposureEvents(request).single;
       expect(exposure, {
@@ -750,20 +750,17 @@ void main() {
 
       final request = _evaluationRequests(requests).single;
       expect(
-        request.url.toString(),
-        'https://browser-intake-datadoghq.com/api/v2/flagevaluation?ddsource=dart-client',
+        '${request.url.origin}${request.url.path}',
+        'https://browser-intake-datadoghq.com/api/v2/flagevaluation',
       );
-      expect(request.headers['Content-Type'], 'application/json');
-      expect(request.headers['DD-API-KEY'], 'client-token');
-      expect(request.headers['DD-EVP-ORIGIN'], 'dart-client');
-      expect(request.headers['DD-EVP-ORIGIN-VERSION'], datadogFlagsSdkVersion);
-      expect(request.headers['DD-REQUEST-ID'], isNotEmpty);
+      _expectIntakeMetadata(request, nativeContentType: 'application/json');
 
-      final body = jsonDecode(request.body) as Map<String, Object?>;
-      expect(body['context'], _datadogEventContext());
+      if (!isWebFlagsIntake) {
+        final body = jsonDecode(request.body) as Map<String, Object?>;
+        expect(body['context'], _datadogEventContext());
+      }
 
-      final evaluations = (body['flagEvaluations'] as List<Object?>)
-          .cast<Map<String, Object?>>();
+      final evaluations = _flagEvaluationEvents(request);
       expect(evaluations, hasLength(3));
 
       final success = _evaluation(
@@ -780,6 +777,15 @@ void main() {
       expect(success['targeting_key'], 'user-123');
       expect(success['context'], {
         'evaluation': {'plan': 'pro'},
+        if (isWebFlagsIntake)
+          'dd': {
+            'env': 'staging',
+            'service': 'shopping-cart',
+            'version': '1.2.3',
+            'rum': {
+              'application': {'id': 'application-id'},
+            },
+          },
       });
       expect(success.containsKey('runtime_default_used'), isFalse);
 
@@ -821,9 +827,7 @@ void main() {
     await client.shutdown();
 
     final request = _evaluationRequests(requests).single;
-    final body = jsonDecode(request.body) as Map<String, Object?>;
-    final evaluations =
-        (body['flagEvaluations'] as List<Object?>).cast<Map<String, Object?>>();
+    final evaluations = _flagEvaluationEvents(request);
 
     final evaluation = evaluations.single;
     expect(evaluation['flag'], {'key': 'show-paywall'});
@@ -985,10 +989,8 @@ void main() {
     await client.shutdown();
 
     expect(_evaluationRequests(requests), hasLength(2));
-    final secondBody = jsonDecode(_evaluationRequests(requests).last.body)
-        as Map<String, Object?>;
-    final secondEvaluations = (secondBody['flagEvaluations'] as List<Object?>)
-        .cast<Map<String, Object?>>();
+    final secondEvaluations =
+        _flagEvaluationEvents(_evaluationRequests(requests).last);
     expect(secondEvaluations.single['flag'], {'key': 'theme'});
   });
 
@@ -1520,6 +1522,50 @@ List<Map<String, Object?>> _exposureEvents(http.Request request) {
       .toList();
 }
 
+List<Map<String, Object?>> _flagEvaluationEvents(http.Request request) {
+  if (isWebFlagsIntake) {
+    return request.body
+        .split('\n')
+        .where((line) => line.isNotEmpty)
+        .map((line) => jsonDecode(line) as Map<String, Object?>)
+        .toList();
+  }
+  final body = jsonDecode(request.body) as Map<String, Object?>;
+  return (body['flagEvaluations'] as List<Object?>)
+      .cast<Map<String, Object?>>();
+}
+
+void _expectIntakeMetadata(
+  http.Request request, {
+  required String nativeContentType,
+}) {
+  expect(request.url.queryParameters['ddsource'], datadogFlagsSource);
+  if (isWebFlagsIntake) {
+    expect(request.headers['Content-Type'], startsWith('text/plain'));
+    expect(request.headers['DD-API-KEY'], isNull);
+    expect(request.headers['DD-EVP-ORIGIN'], isNull);
+    expect(request.headers['DD-EVP-ORIGIN-VERSION'], isNull);
+    expect(request.headers['DD-REQUEST-ID'], isNull);
+    expect(request.url.queryParameters['dd-api-key'], 'client-token');
+    expect(request.url.queryParameters['dd-evp-origin'], datadogFlagsSource);
+    expect(
+      request.url.queryParameters['dd-evp-origin-version'],
+      datadogFlagsSdkVersion,
+    );
+    expect(request.url.queryParameters['dd-request-id'], isNotEmpty);
+    return;
+  }
+
+  expect(request.headers['Content-Type'], nativeContentType);
+  expect(request.headers['DD-API-KEY'], 'client-token');
+  expect(request.headers['DD-EVP-ORIGIN'], datadogFlagsSource);
+  expect(
+    request.headers['DD-EVP-ORIGIN-VERSION'],
+    datadogFlagsSdkVersion,
+  );
+  expect(request.headers['DD-REQUEST-ID'], isNotEmpty);
+}
+
 Map<String, Object?> _datadogEventContext() {
   return {
     'env': 'staging',