Document subscription handler registration changes

[alexeyzimarev]

Documents the changes from Eventuous/eventuous#577 (fixing Eventuous/eventuous#576) in dotnet-next/whats-new.mdx.

Three entries:

• Breaking changes → One handler type per subscription. Registering the same handler type twice on one subscription now throws instead of silently dispatching every event to the same instance twice.
• New features → Event handlers created by a factory are disposed. The subscription now owns handlers its factories created and disposes them, after the pipe filters have drained. Container-registered and caller-supplied handlers are unchanged.
• Bug fixes → Handlers registered with a factory no longer collapse into one. The actual #576 bug, with the Func<IServiceProvider, IEventHandler> collection that triggers it, plus a note that factory-registered handlers are no longer resolvable by key from the container.

Nothing needed correcting elsewhere — the handler docs only ever covered AddEventHandler<T>() and never described the keyed container registration this changes.

npx astro build passes: 156 pages built.

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PR Summary by Qodo

Document subscription handler registration changes in dotnet-next whats-new

📝 Documentation 🕐 10-20 Minutes

AI Description

• Document breaking change: duplicate handler types per subscription now throw
• Document new ownership: factory-created handlers are disposed by the subscription
• Document bug fix: factory-registered handlers no longer collapse into one instance

Diagram

graph TD
  A["whats-new.mdx"] --> B["Breaking changes"] --> C["One handler type"]
  A --> D["New features"] --> E["Factory handlers disposed"]
  A --> F["Bug fixes"] --> G["Factory handlers no collapse"]
  C --> H["Subscription registration"]
  E --> H
  G --> H
  subgraph Legend
    direction LR
    _doc["Doc page"] ~~~ _sec["Section"] ~~~ _api["API behavior"]
  end

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High-Level Assessment

The following are alternative approaches to this PR:

1. Add details to the subscription handler docs (concept page) instead of release notes

• ➕ More discoverable for users who aren’t reading release notes
• ➕ Allows fuller explanation of ownership/disposal and registration constraints
• ➖ Dilutes the purpose of the whats-new page as a concise change log
• ➖ Requires more restructuring/maintenance to keep conceptual docs in sync across versions

2. Link to upstream PR/issues only, with minimal in-repo text

• ➕ Lower maintenance burden for the docs site
• ➕ Avoids duplicating nuanced container/subscription semantics in prose
• ➖ Forces readers to context-switch to GitHub for critical behavior changes
• ➖ Upstream issue/PR discussions are not optimized as end-user documentation

Recommendation: Keep the detailed explanations and examples in dotnet-next/whats-new.mdx as done here, since these are behavior changes users need to notice during upgrades (breaking change + subtle bug fix). If follow-up docs work is planned, add a short link from the handler/subscription conceptual docs to this entry (or to a future dedicated page) for long-term discoverability.

Files changed (1) +53 / -0

Documentation (1) +53 / -0

whats-new.mdxAdd release notes for subscription handler registration behavioral changes +53/-0

Add release notes for subscription handler registration behavioral changes

• Adds new Breaking changes, New features, and Bug fixes entries documenting subscription handler registration changes. Includes code examples covering duplicate handler type rejection, disposal semantics for factory-created handlers, and the fix for factory-registered handlers collapsing into a single instance (plus the container-resolution consequence).

src/content/docs/dotnet-next/whats-new.mdx

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	eventuous-docs	5e39f93	Commit Preview URL Branch Preview URL	Aug 21 2026, 10:45 AM