Revanth14 opened a new issue, #1869:
URL: https://github.com/apache/iceberg-go/issues/1869
### Apache Iceberg version
None
### Please describe the bug 🐞
### Apache Iceberg version
main (development)
### Please describe the bug
`table.Snapshot.UnmarshalJSON` accepts snapshot JSON when the required
`snapshot-id` or `timestamp-ms` field is missing or null.
Because both fields are decoded directly into non-pointer `int64` values,
missing and null values silently become zero:
```go
var snapshot table.Snapshot
err := json.Unmarshal([]byte(`{
"snapshot-id": null,
"timestamp-ms": 1234,
"manifests": []
}`), &snapshot)
// err == nil
// snapshot.SnapshotID == 0
```
The same happens for `timestamp-ms`. A JSON `null` snapshot is also accepted
and becomes a zero-value `Snapshot`, replacing any value already held by the
receiver.
This affects the table metadata parse path as well. Removing either field
from a snapshot in `table/testdata/TableMetadataV2Valid.json` still allows
`table.ParseMetadata` to succeed. A null entry in the `snapshots` list is also
accepted when it does not trigger another metadata consistency check.
The Iceberg specification requires both fields for format versions 1–3:
https://iceberg.apache.org/spec/#snapshots
Java rejects the same inputs: `SnapshotParser.fromJson` requires an object
and reads both fields using `JsonUtil.getLong`, which rejects missing and null
values:
https://github.com/apache/iceberg/blob/main/core/src/main/java/org/apache/iceberg/SnapshotParser.java
### Impact
Malformed snapshot metadata is silently assigned default identity and
timestamp values:
- A missing `snapshot-id` becomes `0` and can be treated as an actual
snapshot identity.
- A missing `timestamp-ms` becomes the Unix epoch, potentially affecting
time-travel resolution, ordering, inspection, and expiration behavior.
- A null snapshot entry becomes a zero-value snapshot rather than producing
an error.
The existing metadata validation checks duplicate IDs and reference
consistency, but cannot determine whether these fields were present in the
original JSON.
### Expected behavior
Parsing should return an error wrapping `table.ErrInvalidMetadata` when:
- `snapshot-id` is missing or null.
- `timestamp-ms` is missing or null.
- A snapshot document or entry is null.
Explicit numeric zero values should remain distinguishable from missing
fields and continue to parse. Failed unmarshalling should not partially replace
an existing `Snapshot` value.
### Willingness to contribute
I can contribute this fix independently.
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