Ensure additionalTokenRefreshParametersForAuthSession returns a string dictionary

GoogleSignIn/Sources/GIDEMMSupport.h

@@ -34,12 +34,13 @@ NS_ASSUME_NONNULL_BEGIN
                       completion:(void (^)(NSError *_Nullable))completion;
 
 /// Gets a new set of URL parameters that contains updated EMM-related URL parameters if needed.
-+ (NSDictionary *)updatedEMMParametersWithParameters:(NSDictionary *)parameters;
++ (NSDictionary<NSString *,NSString *> *)updatedEMMParametersWithParameters:
+    (NSDictionary *)parameters;
 
 /// Gets a new set of URL parameters that also contains EMM-related URL parameters if needed.
-+ (NSDictionary *)parametersWithParameters:(NSDictionary *)parameters
-                                emmSupport:(nullable NSString *)emmSupport
-                    isPasscodeInfoRequired:(BOOL)isPasscodeInfoRequired;
++ (NSDictionary<NSString *,NSString *> *)parametersWithParameters:(NSDictionary *)parameters
+                                                       emmSupport:(nullable NSString *)emmSupport
+                                           isPasscodeInfoRequired:(BOOL)isPasscodeInfoRequired;
 
 @end
 

GoogleSignIn/Sources/GIDEMMSupport.m

@@ -84,16 +84,16 @@ + (void)handleTokenFetchEMMError:(nullable NSError *)error
   }
 }
 
-+ (NSDictionary *)updatedEMMParametersWithParameters:(NSDictionary *)parameters {
++ (NSDictionary<NSString *,NSString *> *)updatedEMMParametersWithParameters:
+    (NSDictionary *)parameters {
   return [self parametersWithParameters:parameters
                              emmSupport:parameters[kEMMSupportParameterName]
                  isPasscodeInfoRequired:parameters[kEMMPasscodeInfoParameterName] != nil];
 }
 
-
-+ (NSDictionary *)parametersWithParameters:(NSDictionary *)parameters
-                                emmSupport:(nullable NSString *)emmSupport
-                    isPasscodeInfoRequired:(BOOL)isPasscodeInfoRequired {
++ (NSDictionary<NSString *,NSString *> *)parametersWithParameters:(NSDictionary *)parameters
+                                                       emmSupport:(nullable NSString *)emmSupport
+                                           isPasscodeInfoRequired:(BOOL)isPasscodeInfoRequired {
   if (!emmSupport) {
     return parameters;
   }
@@ -109,7 +109,7 @@ + (NSDictionary *)parametersWithParameters:(NSDictionary *)parameters
   if (isPasscodeInfoRequired) {
     allParameters[kEMMPasscodeInfoParameterName] = [GIDMDMPasscodeState passcodeState].info;
   }
-  return allParameters;
+  return [GIDEMMSupport dictionaryWithStringValuesFromDictionary:allParameters];
 }
 
 #pragma mark - GTMAuthSessionDelegate
@@ -128,6 +128,30 @@ - (void)updateErrorForAuthSession:(GTMAuthSession *)authSession
   }];
 }
 
+#pragma mark - Private Helpers
+
++ (NSDictionary<NSString *, NSString *> *)
+    dictionaryWithStringValuesFromDictionary:(NSDictionary *)originalDictionary {
+  NSMutableDictionary<NSString *, NSString *> *stringifiedDictionary =
+      [NSMutableDictionary dictionaryWithCapacity:originalDictionary.count];
+
+  [originalDictionary enumerateKeysAndObjectsUsingBlock:^(NSString *key, id value, BOOL *stop) {
+    if ([value isKindOfClass:[NSString class]]) {
+      stringifiedDictionary[key] = value;
+        return;
+    }
+    if ([value isKindOfClass:[NSNumber class]]) {
+      if (CFGetTypeID((__bridge CFTypeRef)value) == CFBooleanGetTypeID()) {
+        stringifiedDictionary[key] = [value boolValue] ? @"true" : @"false";
+      } else {
+        stringifiedDictionary[key] = [value stringValue];
+      }
+      return;
+    }
+  }];
+  return stringifiedDictionary;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

GoogleSignIn/Sources/GIDJSONSerializer/API/GIDJSONSerializer.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * A protocol for serializing an `NSDictionary` into a JSON string.
+ */
+@protocol GIDJSONSerializer <NSObject>
+
+/**
+ * Serializes the given dictionary into a `JSON` string.
+ *
+ * @param jsonObject The dictionary to be serialized.
+ * @param error A pointer to an `NSError` object to be populated upon failure.
+ * @return A `JSON` string representation of the dictionary, or `nil` if an error occurs.
+ */
+- (nullable NSString *)stringWithJSONObject:(NSDictionary<NSString *, id> *)jsonObject
+                                      error:(NSError *_Nullable *_Nullable)error;
+
+@end
+
+NS_ASSUME_NONNULL_END

GoogleSignIn/Sources/GIDJSONSerializer/Fake/GIDFakeJSONSerializerImpl.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import "GoogleSignIn/Sources/GIDJSONSerializer/API/GIDJSONSerializer.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** A fake implementation of `GIDJSONSerializer` for testing purposes. */
+@interface GIDFakeJSONSerializerImpl : NSObject <GIDJSONSerializer>
+
+/**
+ * An error to be returned by `stringWithJSONObject:error:`.
+ *
+ * If this property is set, `stringWithJSONObject:error:` will return `nil` and
+ * populate the error parameter with this error.
+ */
+@property(nonatomic, nullable) NSError *serializationError;
+
+/** The dictionary passed to the serialization method. */
+@property(nonatomic, readonly, nullable) NSDictionary<NSString *, id> *capturedJSONObject;
+
+@end
+
+NS_ASSUME_NONNULL_END

GoogleSignIn/Sources/GIDJSONSerializer/Fake/GIDFakeJSONSerializerImpl.m

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import "GoogleSignIn/Sources/GIDJSONSerializer/Fake/GIDFakeJSONSerializerImpl.h"
+
+#import "GoogleSignIn/Sources/GIDJSONSerializer/Implementation/GIDJSONSerializerImpl.h"
+#import "GoogleSignIn/Sources/Public/GoogleSignIn/GIDSignIn.h"
+
+@implementation GIDFakeJSONSerializerImpl
+
+- (nullable NSString *)stringWithJSONObject:(NSDictionary<NSString *, id> *)jsonObject
+                                      error:(NSError *_Nullable *_Nullable)error {
+  _capturedJSONObject = [jsonObject copy];
+
+  // Check if a serialization error should be simulated.
+  if (self.serializationError) {
+    if (error) {
+      *error = self.serializationError;
+    }
+    return nil;
+  }
+
+  // If not failing, fall back to the real serialization path.
+  NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonObject
+                                                 options:0
+                                                   error:error];
+  if (!jsonData) {
+      return nil;
+  }
+  return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
+}
+
+@end

GoogleSignIn/Sources/GIDJSONSerializer/Implementation/GIDJSONSerializerImpl.h

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import "GoogleSignIn/Sources/GIDJSONSerializer/API/GIDJSONSerializer.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+extern NSString *const kGIDJSONSerializationErrorDescription;
+
+@interface GIDJSONSerializerImpl : NSObject <GIDJSONSerializer>
+@end
+
+NS_ASSUME_NONNULL_END

GoogleSignIn/Sources/GIDJSONSerializer/Implementation/GIDJSONSerializerImpl.m

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import "GoogleSignIn/Sources/GIDJSONSerializer/Implementation/GIDJSONSerializerImpl.h"
+
+#import "GoogleSignIn/Sources/Public/GoogleSignIn/GIDSignIn.h"
+
+NSString * const kGIDJSONSerializationErrorDescription =
+    @"The provided object could not be serialized to a JSON string.";
+
+@implementation GIDJSONSerializerImpl
+
+- (nullable NSString *)stringWithJSONObject:(NSDictionary<NSString *, id> *)jsonObject
+                                      error:(NSError *_Nullable *_Nullable)error {
+  NSError *serializationError;
+  NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonObject
+                                                     options:0
+                                                       error:&serializationError];
+  if (!jsonData) {
+    if (error) {
+      *error = [NSError errorWithDomain:kGIDSignInErrorDomain
+                                   code:kGIDSignInErrorCodeJSONSerializationFailure
+                               userInfo:@{
+                            NSLocalizedDescriptionKey:kGIDJSONSerializationErrorDescription,
+                                 NSUnderlyingErrorKey:serializationError
+                               }];
+    }
+    return nil;
+  }
+  return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
+}
+
+@end