Fix CaseClauseError in OasisSapphire.get_meta_nonce/3 on RPC errors

[dominicletz]

What

Fixes the root cause of CaseClauseError crashes in DiodeClient.Shell.OasisSapphire.get_meta_nonce/3 when the Sapphire RPC node returns a transient error such as invalid signed simulate call query: base block not found.

Related downstream fix: https://github.com/diodechain/ddrive/pulls (ddrive Model.App.update_nonce/2 workaround can be removed once this ships and mix.lock is bumped).

Root cause

oasis_call/2 can return {:error, reason} when the RPC rejects a simulated call, but get_meta_nonce/3 only matched on integer nonces and :revert. The missing clause raised CaseClauseError, which propagated through callers like UserMonitor.update_user/2.

Change

• get_meta_nonce/3: handle {:error, reason} via meta_nonce_from_call/2 — log a warning and return {:error, reason} instead of crashing.
• send_transaction/5 (meta-transaction path): use with so a failed nonce lookup returns {:error, reason} instead of passing a bad value into create_meta_transaction/6.

Tests

test/oasis_sapphire_test.exs covers:

1. meta_nonce_from_call/2 returns integer nonces unchanged
2. :revert returns 0 with a warning
3. The exact RPC error from production reports returns {:error, reason} with a warning (no raise)
4. send_transaction/5 propagates {:error, reason} when nonce lookup fails

$ mix test test/oasis_sapphire_test.exs
4 tests, 0 failures

[gemini-code-assist]

Code Review

This pull request refactors the meta-transaction flow in OasisSapphire to use a with statement for validating the nonce, extracts the nonce parsing logic into meta_nonce_from_call/2 to handle transient RPC errors, and adds unit tests. The feedback suggests adding a catch-all clause in meta_nonce_from_call/2 to prevent potential CaseClauseError crashes from unexpected results, and pattern matching on {:error, reason} directly instead of using elem/2.

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[gemini-code-assist]

To fully prevent CaseClauseError crashes (which this PR aims to address), it is safer to add a catch-all clause to handle any unexpected results (such as nil, which can be returned by decode_result/2). Additionally, we can match {:error, reason} directly to avoid using elem(error, 1).

    case result do
      nonce when is_integer(nonce) ->
        nonce

      :revert ->
        Logger.warning("Identity contract at #{DiodeClient.Base16.encode(identity)} reverted")
        0

      {:error, reason} = error ->
        Logger.warning(
          "get_meta_nonce: nonce lookup for #{DiodeClient.Base16.encode(identity)} failed: #{inspect(reason)}"
        )

        error

      other ->
        Logger.warning(
          "get_meta_nonce: unexpected result for #{DiodeClient.Base16.encode(identity)}: #{inspect(other)}"
        )

        {:error, {:unexpected_result, other}}
    end