API consolidation: context-first, iter.Seq walkers, slog

[epk]

Summary

Breaking API change that removes ~32 redundant surface points and modernizes the codebase. Net -279 lines across 24 files.

Conn: remove non-Ctx wrappers, rename FooCtx → Foo

Every Conn method existed as both Foo() and FooCtx(ctx, ...). Delete the wrappers, rename FooCtx to Foo. All 22 public Conn methods now take context.Context as first parameter:

AddAuth, AddWatch, RemoveWatch, Children, ChildrenW, Get, GetW, Set, Create, CreateContainer, CreateTTL, CreateProtectedEphemeralSequential, Delete, Exists, ExistsW, GetACL, SetACL, Sync, Multi, MultiRead, IncrementalReconfig, Reconfig

Lock: same consolidation

• Lock(ctx) / Unlock(ctx) / LockWithData(ctx, data) — removed LockCtx, UnlockCtx, LockWithDataCtx

Tree walkers: add iter.Seq, remove channel-based APIs

Add All(ctx) → (iter.Seq, func() error) for iterator-based traversal. Keep Walk(ctx, visitor) for error-aware callback traversal. Remove WalkChan, WalkChanCtx, and VisitEvent struct.

• TreeWalker.All(ctx) → (iter.Seq2[string, *Stat], func() error)
• TreeWalker.Walk(ctx, VisitorFunc) → error
• BatchTreeWalker.All(ctx) → (iter.Seq[string], func() error)
• BatchTreeWalker.Walk(ctx, BatchVisitorFunc) → error

Removed types: VisitorCtxFunc, BatchVisitorCtxFunc, VisitEvent

Removed deprecated APIs

• ConnectWithDialer — use Connect(..., WithDialer(...))

Logger: log → log/slog

• Conn.logger is now *slog.Logger (was custom Logger interface)
• WithLogger accepts *slog.Logger
• SetLogger accepts *slog.Logger
• Removed Logger interface and DefaultLogger variable
• Removed defaultLogger struct from structs.go
• All logger.Printf calls → structured slog.Info/slog.Error
• RefreshDNSHostProvider uses slog.Error directly
• Test/example files: log.Printf → slog.Info/slog.Error

Other cleanup

• Version: replace LessThan/GreaterThan/Equal implementations with Compare using cmp.Compare
• ring_buffer_test.go: use slices.Equal instead of custom slicesEqual helper
• util.go: remove now-unused slicesEqual function
• dnshostprovider.go: found := []string{} → var found []string
• server_help_test.go, server_java_test.go, conn.go: %v → %w in error wrapping
• All test/example call sites updated with context.Background() as first arg

Test plan

• go build ./...
• go vet ./...
• go tool golangci-lint run
• go fix -diff ./...
• go test ./... (requires ZK test cluster)

🤖 Generated with Claude Code

[jpfourny]

You can just delete this file. The cached leaves walker was removed a while ago - this example should have been removed, too.

[jpfourny]

I cannot find anything wrong, other than these are API breaking changes. Mind you, it should be trivial to update downstream consumers.

[epk]

Tested with the CoreDNS MCS plugin, compiles and runs fine