fix: ignore extrinsicIndex in multiBlockMigrations event

[Imod7]

Description

Closes #1538

Issue

In the blocks endpoint, we return a list of extrinsics included in the queried block and under each extrinsic their related event. However, during multiBlockMigrations we encounter cases where events reference extrinsic indexes that do not exist.
In the code, this situation is represented by having an event with :

• phase set as ApplyExtrinsic here (which means we expect an extrinsic associated with this event)
• then we retrieve the extrinsic index here
• the index retrieved in this case is 2 but there is no extrinsic in index 2 so we return an error msg

Proposed Solution

During multiBlockMigrations :

• we ignore the extrinsic index since it is a non existent one anyway
• we also ignore the multiblockmigrations / MigrationAdvanced event (shown in Subscan here) since we cannot associate it with any valid/existing extrinsic.

In the code, we do that by :

• not throwing an error if we find an event with a non existent extrinsic during multiBlockMigrations
• push the event only if the extrinsic is present.

This does not break any past logic since the error message will be thrown in all other cases.

Testing

While connected to Shiden network (e.g. through wss://rpc.shiden.astar.network), query block 7675808 http://127.0.0.1:8080/blocks/7675808.

Before the fix we would get :

Missing extrinsic 2 in block 0xc26eb7b19378e953c80ef9749df2b5ae67a7bdb17b3ad9b9a0ee9c1810438a9f

After the fix :

...
...
"extrinsics": [
    {
      "method": {
        "pallet": "timestamp",
        "method": "set"
      },
     ...
     ...
      },
      "events": [
        {
          "method": {
            "pallet": "system",
            "method": "ExtrinsicSuccess"
          },
...
...
{
      "method": {
        "pallet": "parachainSystem",
        "method": "setValidationData"
      },
...
...
"events": [
        {
          "method": {
            "pallet": "system",
            "method": "ExtrinsicSuccess"
          },

The response now returns correctly the 2 extrinsics present in this block and their associated events. There is also the multiblockmigrations / MigrationAdvanced event (mentioned earlier) but we chose to ignore it since we cannot attach it to any valid/existing extrinsics.

Downside

This solution has the downside that we are not showing an existing event.

Long term Solution

As soon as this PR paritytech/polkadot-sdk#3666 gets merged, I will expect that multiBlockMigrations events will have phase set as ApplyInherent so we will not have this issue for future blocks. However this fix needs to be kept for historic blocks.

Todos

• Added issue New execution phases in blocks endpoint #1542 in Sidecar to track the progress of this polkadot-sdk PR and make the necessary changes as soon as it is applied.

[TarikGul]

👍

[IkerAlus]

LGTM