[firestore-bigquery-change-tracker] initializeLatestView update path mutates the shared RawChangelogViewSchema constant

[cabljac]

Package: @firebaseextensions/firestore-bigquery-change-tracker, src/bigquery/initializeLatestView.ts on next.

The existing-view path aliases the module-level constant and mutates it:

const schema = RawChangelogViewSchema;        // line 77
...
if (config.wildcardIds) {
  schema.fields.push(documentPathParams);     // line 86
}

The create path copies first (const schema = { fields: [...RawChangelogViewSchema.fields] }, line 124), so only the update path leaks. Each initializeLatestView call in the same process with wildcardIds set appends another path_params field to the shared constant. Later readers of RawChangelogViewSchema in the same process see the duplicates, including view.setMetadata({ schema: RawChangelogViewSchema }) on line 144 of the create path.

In a long-lived function instance that initialises more than once (several trackers, or the initBigQuerySync task followed by the trigger) the schema sent to BigQuery grows by one duplicate path_params per init. BigQuery rejects duplicate column names in a schema update, so after the first re-init the update path fails until the instance is recycled.

Fix: copy on the update path the same way the create path does.

const schema = { fields: [...RawChangelogViewSchema.fields] };

And pin it with a test that calls initializeLatestView twice with wildcardIds: true and asserts RawChangelogViewSchema.fields is unchanged.

Found during the adversarial review of #3137. Not reproduced live.