The #2 gap in alknet-call: discovers the remote peer's External operations
via services/list + services/schema and registers them in the connection's
Layer 2 overlay as FromCall-provenance leaves with forwarding handlers. The
discovery mechanism was already implemented in registry/discovery.rs;
from_call is the client-side consumer of that API.
src/client/from_call.rs:
- from_call(connection, FromCallConfig) -> Result<Vec<HandlerRegistration>,
AdapterError>. Calls services/list then services/schema for each op,
rebuilds OperationSpec from the schema JSON (parsing op_type, visibility,
error_schemas, access_control), constructs a forwarding handler that calls
the remote op via CallConnection::call(), and returns FromCall-provenance
bundles (composition_authority: None, scoped_env: None, empty capabilities,
remote_safe: false per ADR-028 §4).
- FromCallConfig { namespace_prefix: Option<String>, operation_filter:
Option<HashSet<String>> } with builder methods.
- v1 defaults (two-way doors recorded in client-and-adapters.md):
- error-on-collision (DC-3/OQ-28): applying the (possibly empty) prefix
produces a name already seen -> AdapterError::Conflict, not silent
overwrite.
- auto-on-reconnect (DC-2/OQ-27): the overlay is per-connection (Layer 2,
ADR-024), so re-import on reconnect is naturally scoped; the assembly
layer calls from_call immediately after connect().
- Forwarding handler captures an Arc<CallConnection> and, on invocation,
calls the remote op and returns its ResponseEnvelope. The
parent_request_id participates in the cross-node abort cascade
(ADR-016 §6) — if the parent is aborted, the cascade reaches this handler
which sends call.aborted to the remote node; cross-node abort is
transparent.
- Trust is transitive (recorded in spec): a from_call-imported op executes
the remote node's code; scoped_env bounds which ops are reachable, not
what they do.
OperationContext.internal is now pub (was pub(crate)) so downstream
consumers (assembly layer, integration tests) can construct contexts for
overlay-env dispatch.
Tests (207 lib + 2 integration):
- Unit: rebuild_spec name/prefix/op_type/visibility/error_schemas/acl;
unknown op_type -> SchemaParse; missing op_type -> SchemaParse;
FromCallConfig builder; from_call against a mock connection returns
DiscoveryFailed (no transport); FromCall provenance + leaf fields + remote_safe false.
- Integration (tests/two_node_call.rs): from_call over a real QUIC loopback
— CallClient connects, from_call discovers server/echo, registers the
bundle in the overlay, and the forwarding handler round-trips an input
through the overlay env to the remote op and back.
clippy + fmt + test all green.
Refs: tasks/call/client/from-call.md
Refs: docs/architecture/decisions/017-call-protocol-client-and-adapter-contract.md §3, §6
Refs: docs/architecture/crates/call/client-and-adapters.md §from_call
glm-5.2
a3825f57cf