Safeguard against multiple header values.

Author: kinyoklion

packages/common_client/lib/src/data_sources/get_environment_id.dart

@@ -1,6 +1,15 @@
 const _envIdHeader = 'x-ld-envid';
 
+final _splitRegex = RegExp(r'\s*,\s*');
+
 /// Get the environment ID from headers.
 String? getEnvironmentId(Map<String, String>? headers) {
-  return headers?[_envIdHeader];
+  // Headers will always be in lower case from the http response.
+  // If multiple headers are associated with a single key, then they will be
+  // in a comma separated list with potential whitespace.
+  final headerValue = headers?[_envIdHeader];
+  if (headerValue == null) {
+    return null;
+  }
+  return headerValue.split(_splitRegex).first;
 }

packages/common_client/test/data_sources/data_source_event_handler_test.dart

@@ -46,12 +46,6 @@ void main() {
               '"variation":0,"trackEvents":false}'
               '}');
 
-      final bob = flagManager!.get('HasBob')!.flag!;
-      expect(bob.version, 11);
-      expect(bob.detail.value, LDValue.ofBool(false));
-      expect(bob.detail.variationIndex, 1);
-      expect(bob.detail.reason, isNull);
-
       final killSwitch = flagManager!.get('killswitch')!.flag!;
       expect(killSwitch.version, 10);
       expect(killSwitch.detail.value, LDValue.ofBool(true));

packages/common_client/test/data_sources/get_environment_id_test.dart

@@ -2,40 +2,42 @@ import 'package:test/test.dart';
 import 'package:launchdarkly_common_client/src/data_sources/get_environment_id.dart';
 
 void main() {
-  group('getEnvironmentId', () {
-    test('returns environment ID from headers', () {
-      final headers = {'x-ld-envid': 'test-env-123'};
-      final result = getEnvironmentId(headers);
-      expect(result, 'test-env-123');
-    });
+  test('returns environment ID from headers', () {
+    final headers = {'x-ld-envid': 'test-env-123'};
+    final result = getEnvironmentId(headers);
+    expect(result, 'test-env-123');
+  });
 
-    test('returns null when header is missing', () {
-      final headers = <String, String>{'other-header': 'value'};
-      final result = getEnvironmentId(headers);
-      expect(result, null);
-    });
+  test('returns null when header is missing', () {
+    final headers = <String, String>{'other-header': 'value'};
+    final result = getEnvironmentId(headers);
+    expect(result, null);
+  });
 
-    test('returns null when headers are null', () {
-      final result = getEnvironmentId(null);
-      expect(result, null);
-    });
+  test('returns null when headers are null', () {
+    final result = getEnvironmentId(null);
+    expect(result, null);
+  });
 
-    test('returns null when headers are empty', () {
-      final headers = <String, String>{};
-      final result = getEnvironmentId(headers);
-      expect(result, null);
-    });
+  test('returns null when headers are empty', () {
+    final headers = <String, String>{};
+    final result = getEnvironmentId(headers);
+    expect(result, null);
+  });
 
-    test('handles case-sensitive header name correctly', () {
-      final headers = {'X-LD-ENVID': 'test-env-123'};
-      final result = getEnvironmentId(headers);
-      expect(result, null);
-    });
+  test('handles multiple values for environment id', () {
+    // Services should only send a single environment ID, but if we did get
+    // multiple we want it to be handled safely.
+    final headers = <String, String>{'x-ld-envid': 'envid-a, envid-b'};
+    final result = getEnvironmentId(headers);
+    expect(result, 'envid-a');
+  });
 
-    test('handles environment ID with special characters', () {
-      final headers = {'x-ld-envid': 'env-123-abc-456'};
-      final result = getEnvironmentId(headers);
-      expect(result, 'env-123-abc-456');
-    });
+  test('handles envid is empty string', () {
+    // Services shouldn't send an empty string, but we want to ensure it
+    // doesn't cause any runtime issue.
+    final headers = <String, String>{'x-ld-envid': ''};
+    final result = getEnvironmentId(headers);
+    expect(result, '');
   });
 }