Enforce complexity, shadowing, block statement, useless else and readonly rules with Biome

[cristianrgreco]

Summary

Enables five more Biome rules at error. Every existing violation is fixed: there is no biome-ignore, no per-file exemption, and none of the five is turned off for **/*.test.ts.

Builds on #1585, which has merged. Hits are from biome lint --only=<rule> --max-diagnostics=none ., before on the #1585 branch and after on this one.

Rule	Before: source	Before: *.test.ts	After
complexity/noExcessiveCognitiveComplexity (default max 15)	2 in 2 files	0	0
suspicious/noShadow	12 in 8 files	12 in 8 files	0
style/noUselessElse	25 in 16 files	1	0
style/useBlockStatements	28 in 9 files	6 in 2 files	0
style/useReadonlyClassProperties	8 in 5 files	0	0

Cognitive complexity

Function	Score before	Fix
CouchbaseContainer.configureExternalPorts	16	The five per-service blocks move, unchanged, into a private setServicePorts(body, container) placed below it.
ImageName constructor	20	The code that builds string moves into a private buildString() placed below it.

• setServicePorts scores exactly 15, the limit.
• buildString returns the value and the constructor assigns it. The branches could not be moved as they were, because string is readonly and can only be assigned in the constructor. Each this.string = x became return x, in the same order.

Shadowing

The inner binding is renamed in every case but one.

File	Rename
gcloud/src/spanner-emulator-helper.ts	the Spanner class from the dynamic import is aliased to SpannerClient; the Spanner type import is unchanged
toxiproxy/src/toxiproxy-container.ts	reduce callback parameter port to candidatePort
container-runtime/auth/get-auth-config.ts	parseDockerConfig parameter dockerConfig to json
container-runtime/clients/container/docker-container-client.ts	processStream parameter stream to source
port-forwarder/port-forwarder.ts	find callback parameter port to mapping
reaper/reaper.ts (5 hits)	module-level let sessionId to reaperSessionId
utils/test-helper.ts	predicate parameter status to running
wait-strategies/startup-check-strategy.ts	predicate parameter startupStatus to status
hivemq and mosquitto tests (3 hits)	message handler parameter message to payload
kurrentdb test	getStreamFirstEvent parameter stream to subscription
common/retry.test.ts (3 hits)	predicate parameter result to value
container-runtime/auth/credential-provider.test.ts	test-local credentialProvider to unnamedCredentialProvider
docker-compose-environment.test.ts (2 hits), generic-container.test.ts	nested await using _ to _pulled
generic-container-logs.test.ts	data handler parameter line to chunk

reaper.ts is the exception: the outer, unexported variable is renamed. Two of the five inner bindings are the sessionId parameter properties of RyukReaper and DisabledReaper, which implement Reaper.sessionId, so they cannot be renamed.

Useless else and block statements

Both are Biome autofixes, applied with --write --unsafe and then read line by line.

• noUselessElse: every site is an else after a branch that ends in return or throw. The else body moves out one level.
• useBlockStatements: braces are added around single-statement if and else bodies.

Readonly class properties

By default the rule checks private properties only. All eight are assigned in the initialiser or constructor and nowhere else, so all eight are now readonly.

Class	Fields
AzureCosmosDbEmulatorContainer	key, explorerEnabled, portGenerator
MSSQLServerContainer	username
NatsContainer	args, values
DockerComposeEnvironment	waitStrategy
SocatContainer	targets

• args, values, waitStrategy and targets are collections that are mutated but never reassigned.
• key, explorerEnabled and username have no setter, so they were already constants.
• No field is written through Object.assign, an index signature or a cast.

Verification

• npm run format: no changes.
• npm run lint and npm run lint:ci: pass.
• npm run knip: pass.
• npm run check-compiles: pass.
• biome lint --only=<rule> . for each of the five rules: 0 hits.
• The five checks above were rerun after merging main (Enforce function length, nullish coalescing and no-console with Biome #1585 squashed, v12.2.1, Add a write-code skill for code conventions #1517). The merge conflicted in biome.json and http-wait-strategy.ts, where main had the Enforce function length, nullish coalescing and no-console with Biome #1585 version of lines this PR changes; this branch's side is kept in both. git diff origin/main...HEAD is 44 files.

Local tests

The test files covering the changed files were run as two Vitest processes at the same time. The Docker host has 4 GB of memory and was shared with other sessions, which had five Couchbase containers running. No failure has been compared against the base branch yet.

Core, 25 files: 24 passed, 1 failed (272 tests passed, 1 failed, 1 skipped).

Test	Error	Rerun alone
generic-container.test.ts > should return first mapped port with regardless of protocol	Test timed out in 180000ms	passed

Modules, 15 files: 8 passed, 7 failed (66 tests passed, 12 failed). The 8 that passed: cloudstorage-emulator-container, emulator-flags-manager, spanner-emulator-helper, kurrentdb-container, mongodb-container, mosquitto-container, nats-container, toxiproxy-container.

File	Failed tests	Error	Rerun alone
redis-container.test.ts	1	read ECONNRESET	passed, 12 of 12
hivemq-container.test.ts	1	Get "https://registry-1.docker.io/v2/": net/http: TLS handshake timeout	passed, 1 of 1
azurite-container.test.ts	1	RestError with an empty message	passed, 9 of 9
postgresql-container.test.ts	1	connect ECONNREFUSED 127.0.0.1:61302	passed, 8 of 8
mongodb-atlas-local-container.test.ts	2	container … is not running (HTTP 409); cannot query search index … while in state UNKNOWN	not rerun
azure-cosmosdb-emulator-container.test.ts	2	schema "cosmos_api" does not exist	not rerun
mssqlserver-container.test.ts	4	Log stream ended and message "/.*Recovery is complete.*/" was not received (3); the same for /.*Attribute synchronization manager initialized*/ (1)	not rerun

Not run locally: couchbase-container.test.ts, which covers configureExternalPorts. CI runs it.

Not breaking

• No export is added, removed or renamed, and no public method or constructor signature changes.
• The two new methods (setServicePorts, buildString) and the eight readonly fields are private.
• The other changes are local renames, added braces and removed else keywords. Control flow is the same.
• The HiveMQ, Mosquitto and KurrentDB docs pages include the renamed test lines, so those snippets show payload and subscription.