# Description
Nullable reference types are now enabled once, in `common.props`, and
every project in the repository builds warning-clean with them.
**Configuration**
- `<Nullable>enable</Nullable>` lives in `common.props`. All per-project
`<Nullable>` settings are removed: 178 project files (enable,
annotations, and the `disable` in the three Aot test projects).
- 419 per-file `#nullable enable`/`restore` directives and the 4
`#nullable disable` directives are removed.
- Kept on purpose:
- The 5 `<auto-generated>` schema files (`UANodeSet.cs`, `UA Type
Dictionary.cs`, `OPCBinarySchema.cs`, `SecuredApplication.cs`,
`PInvokeHelper.cs`) keep `#nullable enable`. The compiler ignores the
project setting in generated code, so the directive is required there.
- `tests/Opc.Ua.Interop.LegacyPeer` keeps `disable`. It builds against
the 1.5.378 packages and does not import the repository props.
- `docs/DeveloperGuide.md` and `.github/copilot-instructions.md` now
describe the central setting.
**Migration** (the 43 unset and 13 annotations-only projects, roughly
10k diagnostics)
- **Production code: annotated at the declarations.** Covers
`tools/Opc.Ua.SourceGeneration.Core`, `src/Opc.Ua.Lds.Server` and the
LDS sample.
- Members, parameters and returns are nullable where null actually
flows.
- Null-check helpers carry `[NotNullWhen]` (`IsNull`, `IsValidXmlName`,
`IsMethodTypeDesign`).
- `CoreUtils.Format`, `Utils.Format`, `ITemplateWriter.WriteLine` take
`params object?[]`. `Template.AddReplacement` takes `string?` (rendering
already skips null replacements).
- `IRegisteredServerStore.RegisterAsync` returns
`Task<RegistrationEntry?>`: it returns null when a registration is
removed.
- Dereferences backed by an invariant (for example, the validated model)
use `!`, so runtime behaviour is unchanged.
- **Behavioural changes in production code** (small, deliberate):
- `NodeSetToModelDesign` throws `InvalidOperationException` when the
file is not a NodeSet. Before, it threw a NullReferenceException on the
next line.
- `ModelDesignValidator` starts its lookup tables empty instead of null.
A redundant `if (m_nodes == null) return;` guard is gone.
- **Test code: minimal annotations.**
- `?` on values that can be null, `!` where the test asserts non-null.
- `= null!` for fixture members assigned in SetUp.
- `TryGetStructure<T>(out T? x)` where the inferred `T?` broke the
`IEncodeable` constraint.
- A few redundant `== null` checks on structs (`NodeId`, `ArrayOf<T>`)
folded into the adjacent `IsNull`/`Count` checks.
**Notes for reviewers**
- The diff is large (~1,500 files) but almost entirely mechanical: `?`,
`!` and directive removal. The non-annotation changes are listed above.
- Known follow-up, not done here:
`IModelDesign.Namespaces/TargetNamespace/NamespaceUris` stay
non-nullable even though the validator returns null before it loads a
dictionary. Making them nullable would ripple through every generator
call site.
## Related Issues
- Fixes#4439
## Checklist
- [ ] I have signed the
[CLA](https://opcfoundation.org/license/cla/ContributorLicenseAgreementv1.0.pdf)
and read the
[CONTRIBUTING](https://github.com/OPCFoundation/UA-.NETStandard/blob/master/CONTRIBUTING.md)
doc.
- [ ] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
- [x] I have added all necessary documentation.
- [x] I have verified that my changes do not introduce (new) build or
analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
at least .net **framework** and .net **10**, and all passed.
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.
The "no new warnings" box covers net10.0 and net48: full non-incremental
builds of `UA.slnx`, `tools/SourceGeneration.slnx`,
`tools/MigrationAnalyzer.slnx` and the Aot test projects finished with 0
warnings and 0 errors under the repository's warnings-as-errors
settings. net9.0 and net8.0 also had no nullable diagnostics, but they
were not rebuilt after the final fixes. Tests have not been run locally
yet.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
# Description
Release the loopback port reservation immediately before the discovery
failure
attempt in `DiscoveryFailureDoesNotInterruptHealthyClientAsync`.
Keeping a TCP socket bound but non-listening does not guarantee prompt
connection
refusal on Darwin: the macOS CI attempts remain pending until caller
cancellation.
The test is intended to exercise refusal and healthy-client isolation,
not that
platform-specific socket state.
The change is confined to the fixture. It retains the exact
`BadNotConnected`
and inner `SocketException` assertions, the real healthy-client
`GetEndpoints`
readback, the separate caller-cancellation case and the existing
timeout. There is
no retry, skipped platform or production-code change.
The reservation is kept until the last possible moment, immediately
before the
attempt. As with ordinary released-ephemeral-port fixtures, another
local process
could claim that port; the original assertions will still fail rather
than hide
an unexpected outcome.
## Related Issues
Fixes#4558. This focused upstream correction is separate from the
UaLens delivery
in #4462.
## Validation
- Windows net10.0: refusal and cancellation tests passed in three
consecutive runs.
- Windows net48: the same two tests passed.
- The formerly failing macOS Sessions lane now passes in
[CI run
36396834698](https://github.com/OPCFoundation/UA-.NETStandard/actions/runs/36396834698/job/108845243883).
The other test/build checks and coverage pass; CodeQL was still running
at the
latest check. No maintainer approval or merge is implied.
- Existing tests, assertions and CI policy are unchanged.
## Checklist
- [ ] CLA prerequisite confirmed by the contributor/service.
- [x] Existing exact behavioral regressions retained and run locally.
- [x] Added the explanation at the non-obvious fixture boundary.
- [x] Targeted builds introduce no compiler/analyzer warnings.
- [ ] All UA.slnx tests run locally on .NET Framework and .NET 10.
- [ ] New macOS CI and CodeQL checks confirmed successful.
- [ ] Maintainer feedback addressed and current approval obtained.
The PR was made ready for review through a separate manual action. No
automatic
merge was performed. Maintainer acceptance is still required before
integration
into #4462 under the approved closure sequence.
## Summary
Translate socket and I/O connection failures into
`ServiceResultException(BadNotConnected)` at
`UaSCUaBinaryClientChannel.ConnectAsync`, so public discovery creation
does not leak raw transport exceptions.
- Preserve the original exception as `InnerException` for diagnostics.
- Keep the existing operation fault, channel shutdown and operation
completion paths.
- Leave cancellation, existing `ServiceResultException`
instances/statuses, and programming errors unchanged.
- Do not change the lower-level byte transport contract or reconnect
behavior.
Fixes#4535
## Regression Coverage
- Deterministic injected HostNotFound, ConnectionRefused, socket timeout
and IOException failures assert BadNotConnected, exact inner cause and
closed transport/channel.
- Separate controls assert caller cancellation and unchanged
service/programming exceptions.
- Public `DiscoveryClient.CreateAsync` integration uses a bound,
non-listening loopback port. It asserts the translated failure and
verifies a previously connected discovery client can still retrieve
endpoints afterward. A separate public-API cancellation control remains
a cancellation.
- No live DNS lookup is required in the committed tests; DNS failure is
injected deterministically.
## Validation
Base `b4136d8e9`, Windows Release:
| Focused selection | net10.0 | net48 |
| --- | ---: | ---: |
| UaSCBinaryClientChannelDeterministicTests + TcpByteTransportTests | 51
passed | 51 passed |
| SessionlessInvocationTests | 22 passed | 22 passed |
All four selections exited 0, with zero failures/skips. Changed-file
whitespace verification, diagnostics and `git diff --check` passed.
Before the fix, the seven new deterministic cases produced 4
raw-transport failures / 3 passing controls. The two new public-API
cases produced 1 raw SocketException failure / 1 cancellation-control
pass with only the production fix reversed. The source fix was restored,
rebuilt, and the full focused selections above passed.
The complete framework/platform matrix is left to PR CI. No repository
guidance, feed configuration, security policy or unrelated consumer
workaround was changed.
---------
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
romanett