fix: allow '/' characters in Firestore map keys

packages/google_cloud_firestore/lib/src/field_value.dart

@@ -440,14 +440,17 @@ void _validateUserInput(
 
     case Map<Object?, Object?>():
       for (final entry in value.entries) {
+        final keyPath = switch (entry.key) {
+          final FieldPath fp => fp,
+          final String s => FieldPath([s]),
+          _ => FieldPath([entry.key.toString()]),
+        };
         _validateUserInput(
           arg,
           entry.value,
           description: description,
           options: options,
-          path: path == null
-              ? FieldPath.from(entry.key)
-              : path._appendPath(FieldPath.from(entry.key)),
+          path: path == null ? keyPath : path._appendPath(keyPath),
           level: level + 1,
           inArray: inArray,
         );

packages/google_cloud_firestore/test/integration/firestore_test.dart

@@ -34,5 +34,38 @@ void main() {
 
       expect(collections, containsAll([a, b]));
     });
+
+    group('map keys with "/" characters', () {
+      test('set() round-trips a map with "/" in key', () async {
+        final docRef = firestore.doc('activities/new-activity');
+
+        await docRef.set({
+          'activityType': 'activityA',
+          'agents': {'products/product-a': 5.0},
+        });
+
+        final data = (await docRef.get()).data()!;
+        expect(data['activityType'], 'activityA');
+        expect(
+          (data['agents']! as Map<String, Object?>)['products/product-a'],
+          5.0,
+        );
+      });
+
+      test('update() round-trips a map value with "/" in key', () async {
+        final docRef = firestore.doc('activities/update-activity');
+        await docRef.set({'activityType': 'activityA'});
+
+        await docRef.update({
+          'agents': {'products/product-b': 10.0},
+        });
+
+        final data = (await docRef.get()).data()!;
+        expect(
+          (data['agents']! as Map<String, Object?>)['products/product-b'],
+          10.0,
+        );
+      });
+    });
   });
 }

packages/google_cloud_firestore/test/unit/firestore_test.dart

@@ -185,6 +185,39 @@ void main() {
         final batch = firestore.batch();
         expect(batch, isA<WriteBatch>());
       });
+
+      group('set() with map keys containing "/"', () {
+        test('accepts a top-level map value with "/" in key', () {
+          final firestore = Firestore(
+            settings: const Settings(projectId: 'test'),
+          );
+          final batch = firestore.batch();
+          final docRef = firestore.doc('activities/new-activity');
+
+          expect(
+            () => batch.set(docRef, {
+              'activityType': 'activityA',
+              'agents': {'products/product-a': 5.0},
+            }),
+            returnsNormally,
+          );
+        });
+
+        test('accepts nested maps with "/" in keys', () {
+          final firestore = Firestore(
+            settings: const Settings(projectId: 'test'),
+          );
+          final batch = firestore.batch();
+          final docRef = firestore.doc('col/doc');
+
+          expect(
+            () => batch.set(docRef, {
+              'refs': {'users/alice': true, 'users/bob': false},
+            }),
+            returnsNormally,
+          );
+        });
+      });
     });
 
     group('bulkWriter()', () {