fix(firestore): fix an issue that would cause FieldValue.increment to not work for big int

[Lyokone]

Description

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Related Issues

closes #12318

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Breaking Change

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[nbergemann]

Hello,

I've observed a change in behavior when using FieldValue.increment(1) with cloud_firestore after updating to a new version. Previously, when incrementing a field in Firestore, the incremented value would be received as an integer. However, now it appears to be received as a double.

The relevant code modification seems to be in packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/method_channel/utils/firestore_message_codec.dart, where an adjustment was made to handle FieldValueType.incrementInteger as (delegate.value as int).toDouble() internally, to avoid precision loss:

} else if (value is FieldValuePlatform) {
    MethodChannelFieldValue delegate = FieldValuePlatform.getDelegate(value);
    final int code = _kFieldValueCodes[delegate.type]!;
-    buffer.putUint8(code);
-    if (delegate.value != null) writeValue(buffer, delegate.value);
+    if (delegate.type == FieldValueType.incrementInteger) {
+        buffer.putUint8(_kIncrementDouble);
+        writeValue(buffer, (delegate.value as int).toDouble());
+    } else {
+        buffer.putUint8(code);
+        if (delegate.value != null) writeValue(buffer, delegate.value);
+    }
}

Is this change intentional? It seems to introduce inconsistencies with how incremental updates are handled and serialized. For a temporary workaround, I've specified cloud_firestore_platform_interface: 6.1.7 in my pubspec.yaml.

Could someone clarify if this is the intended behavior moving forward and suggest how we might adjust our code to accommodate this change effectively?

Thank you.

[nekooooo0203]

as double? causes error, type 'int' is not a subtype of type 'double?' in type cast
as int? causes error, type 'double' is not a subtype of type 'int?' in type cast

[Lyokone]

Already reported and tracked here: #12436