Phoebe Goldman ecc00cae40 Add reducer name to database log records (#3274) ...

# Description of Changes

Extends log records with a new field, `function`, which stores the name
of the reducer being executed when the log was produced. I have chosen
to name this field `function` rather than `reducer` because we will soon
be adding procedures, which are not reducers but will also be valid
values for this field.

While making this change, I noticed inconsistent values for injected
logs. Previously, we injected logs in three places, with different
values for the record fields:

1. `SystemLogger` (used when publishing and updating) set `filename:
Some("spacetimedb")` and `target: None`.
2. `log_reducer_error` (used for reducer error returns) set `filename:
None` and `target: Some(reducer)`, with `reducer` being the name of the
reducer.
3. `ModuleHost::inject_logs` (used for calls to nonexistent reducers and
calls with ill-typed arguments) set `filename: Some("external")` and
`target: None`.

With this change, I have decided that injected logs universally have
`filename: Some("__spacetimedb__")` and `target:
Some("__spacetimedb__")`. I have chosen the double-underscore convention
for reserved names to avoid confusion should a user name a source file
or reducer `spacetimedb`. I am not terribly attached to using
`spacetimedb` here, and would be happy to change to some other string,
like `internal` or `system`.

I have further decided that `log_reducer_error` and `inject_logs` both
have access to a sensible non-`None` value for `function` and so should
set it to the name of the reducer. The `target` field is not used for
this. Note that in cases where a client attempts to call a non-existent
reducer, the `function` field of the log record will be set to that
client-supplied non-existent reducer name.

# API and ABI breaking changes

Changes our log record format. This is at least backwards-compatible (as
in, newer consumers can read older logs) because the new field is
optional. I am unsure if it is forwards-compatible (as in, older
consumers reading newer logs) because I don't know if `serde_json` will
ignore unknown fields or will error.

# Expected complexity level and risk

1

# Testing

- [x] Manually ran `quickstart-chat` (modified to log messages and name
changes) and saw sensible output.

2025-09-23 16:01:26 +00:00

..

lib.rs

Add reducer name to database log records (#3274)

2025-09-23 16:01:26 +00:00