Don't require selectedChannel when deserializing channel data

[Corina (corinagum)]

TeamsChannelDataSettings.SelectedChannel was declared required, and System.Text.Json enforces required members (.NET 7+). A channelData.settings of {} therefore threw:

JsonException: JSON deserialization for type 'Settings' was missing required properties including: 'selectedChannel'.

Found while investigating teams.py#563, where the Teams service sent channelData.app  as  {} . .NET was otherwise unaffected; every other channel-data property is already nullable, but SelectedChannel was the one strict field and would fail the same way.

This is latent rather than actively reported: settings appears less often than app. Fixing it now avoids the same class of outage.

Change

 public required TeamsChannel SelectedChannel  > public TeamsChannel? SelectedChannel

Inbound models shouldn't enforce required fields on service-provided data. No consumers of SelectedChannel exist in  src/, test/, or Samples/ .

Tests

New TeamsChannelDataDeserializationTests.cs empty app / channel / team / tenant / settings  all deserialize,  SelectedChannel  is null for empty settings, and populated values round-trip.

Validation

• Build: 0 warnings, 0 errors
• 522 tests pass (net10.0)
• No net new format issues

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[Copilot]

Pull request overview

This PR removes required from TeamsChannelDataSettings.SelectedChannel to prevent System.Text.Json from throwing when the Teams service provides channelData.settings (and similar nested objects) as {}. This aligns the inbound schema with real-world service payloads and avoids deserialization outages on newer runtimes that enforce required members.

Changes:

• Relax TeamsChannelDataSettings.SelectedChannel from required TeamsChannel to nullable TeamsChannel? to allow empty settings objects.
• Add unit tests covering empty nested channelData objects (app, channel, team, tenant, settings) and ensuring populated values deserialize correctly.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
test/Microsoft.Teams.Apps.UnitTests/TeamsChannelDataDeserializationTests.cs	Adds deserialization regression coverage for empty nested channelData objects and verifies SelectedChannel null/preserved behavior.
src/Microsoft.Teams.Apps/Schema/TeamsChannelData.cs	Makes SelectedChannel nullable to avoid required-member deserialization failures for service-provided {} payloads.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Kavin (singhk97)]

nice proactive fix. can you elaborate on the scenario where this field is omitted