panic when using watch schema cache with postgres

[vroldanbet]

What platforms are affected?

macos

What architectures are affected?

arm64

What SpiceDB version are you using?

v1.40.0

Steps to Reproduce

A discord user reported a panic when using the watch schema cache.

From the stacktrace, what we can see is the postgres Watch API is returning a datastore.RevisionChanges that has a nil Revision, and causes it to panic when logging the revision change here and attempting to log the nil revision.

{"level":"info","revision":"CNT9lQM=","count":0,"time":"2025-02-18T13:34:11Z","message":"populated caveat watching cache"}
{"level":"debug","revision":"CNT9lQM=","watch-heartbeat":60000,"time":"2025-02-18T13:34:11Z","message":"beginning schema watch"}
{"level":"debug","time":"2025-02-18T13:34:11Z","message":"schema watch started"}
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x134ff0a]
goroutine 706 [running]:
github.com/authzed/spicedb/pkg/datastore.(*RevisionChanges).MarshalZerologObject(0x0, 0xc000b7a230)
    /home/runner/actions-runner/_work/spicedb/spicedb/pkg/datastore/datastore.go:72 +0x2a
github.com/rs/zerolog.(*Event).appendObject(0xc000b7a230, {0x3a759e0?, 0x0?})
    /home/runner/go/pkg/mod/github.com/rs/[email protected]/event.go:211 +0xa5
github.com/rs/zerolog.(*Event).Object(0xc000b7a230, {0x3473354?, 0x0?}, {0x3a759e0, 0x0})
    /home/runner/go/pkg/mod/github.com/rs/[email protected]/event.go:227 +0x18b
github.com/authzed/spicedb/internal/datastore/proxy/schemacaching.(*watchingCachingProxy).startSync.func2()
    /home/runner/actions-runner/_work/spicedb/spicedb/internal/datastore/proxy/schemacaching/watchingcache.go:264 +0xabd
created by github.com/authzed/spicedb/internal/datastore/proxy/schemacaching.(*watchingCachingProxy).startSync in goroutine 623
    /home/runner/actions-runner/_work/spicedb/spicedb/internal/datastore/proxy/schemacaching/watchingcache.go:185 +0x20f
Starting service..........Max attempts reached

Expected Result

No panic and no datastore.RevisionChange with a nil revision

Actual Result

server panics

[vroldanbet]

I believe this was fixed in 1.40.1, closing