Add debug-level summary log of back-compatibility changes in http-client-csharp generator by Copilot · Pull Request #10415 · microsoft/typespec

Copilot · 2026-04-17T17:50:36Z

Back-compatibility adjustments driven by a library's LastContractView (parameter reorders, renamed/preserved params, collection type preservation, constructor promotions, enum reorders, added api-version members, model-factory shims, etc.) were hard to spot in generator run logs. This adds a single human-readable summary listing every such change at the end of generation, emitted through the existing logging pipeline.

Changes

Extended Emitter (Microsoft.TypeSpec.Generator.EmitterRpc) with categorized, buffered logging:
- New overloads Info(string, BackCompatibilityChangeCategory), Debug(string, BackCompatibilityChangeCategory), Verbose(string, BackCompatibilityChangeCategory) that buffer messages and dedup them per (level, category).
- New WriteBufferedMessages() API that emits a single grouped trace per level via the existing JSON-RPC channel.
- Buffered messages are also auto-flushed on Emitter.Dispose as a safety net.
- Header wording uses conditional singular/plural based on the count (e.g. 1 message across 1 category vs N messages across M categories).
New BackCompatibilityChangeCategory enum (Microsoft.TypeSpec.Generator.EmitterRpc): strongly-typed set of categories used by the buffered overloads; display names are mapped centrally inside Emitter.
CSharpGen.ExecuteAsync: calls Emitter.WriteBufferedMessages() after all ProcessTypeForBackCompatibility runs.
Instrumented back-compat sites to record their decisions (each call now goes through Emitter.Debug/Info with a BackCompatibilityChangeCategory value):
- ClientProvider — method parameter reordering
- RestClientProvider — paging param name preservation (top, maxPageSize casing)
- ScmModelProvider — AdditionalProperties shape preservation
- ModelProvider — collection property type preservation; abstract-model ctor modifier promotion
- ModelFactoryProvider — back-compat method add / replace / skip
- FixedEnumProvider — enum member reordering
- ApiVersionEnumProvider — api version members carried over from last contract
Unit tests added to EmitterTests covering buffering, dedup, null/empty handling, level separation, and reset.

Example output

Summary of grouped 'debug' messages: 4 messages across 3 categories.
  Method Parameter Reordering (2):
    - Reordered parameters of 'FooClient.GetData' to match last contract.
    - Reordered parameters of 'FooClient.UpdateData' to match last contract.
  Parameter Name Preserved (1):
    - Preserved parameter name 'top' on 'FooClient' from last contract (instead of 'maxCount').
  Collection Property Type Preserved (1):
    - Changed property 'Bar.Items' type to 'IReadOnlyList<string>' to match last contract.

Back-compat summaries are emitted at debug level, so they are surfaced only when logLevel: debug (or verbose) is set on the emitter.

…y changes Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/b2456212-73e8-4f37-b9e5-de37fa8f42d5 Co-authored-by: jorgerangel-msft <102122018+jorgerangel-msft@users.noreply.github.com>

Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/b2456212-73e8-4f37-b9e5-de37fa8f42d5 Co-authored-by: jorgerangel-msft <102122018+jorgerangel-msft@users.noreply.github.com>

Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/357d37d4-17ca-47cc-aeb3-f6585651cbe9 Co-authored-by: JoshLove-msft <54595583+JoshLove-msft@users.noreply.github.com>

Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/67866439-1d0c-40a7-924d-f83a39135c1c Co-authored-by: JoshLove-msft <54595583+JoshLove-msft@users.noreply.github.com>

pkg-pr-new · 2026-04-17T18:45:10Z

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/http-client-csharp@10415

commit: 221ab52

Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/7c6d8338-34c2-426d-bf0a-8503bfc13355 Co-authored-by: JoshLove-msft <54595583+JoshLove-msft@users.noreply.github.com>

Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/3ef978ca-05c9-4720-b536-e9b068a289d8 Co-authored-by: JoshLove-msft <54595583+JoshLove-msft@users.noreply.github.com>

Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/1cb1f965-9936-49a9-8b75-7e402188b812 Co-authored-by: JoshLove-msft <54595583+JoshLove-msft@users.noreply.github.com>

jorgerangel-msft · 2026-04-20T17:07:23Z

+                    return;
+                }
+
+                snapshot = new Dictionary<string, Dictionary<BackCompatibilityChangeCategory, SortedSet<string>>>(_bufferedMessages, StringComparer.Ordinal);


why can't we just read the bufferedMessages directly instead of creating another copy of it?

Done in 221ab52 — removed the snapshot copy. The loop now iterates _bufferedMessages directly under the lock and clears it at the end. --generated by Copilot

jorgerangel-msft · 2026-04-20T17:10:33Z

+                }
+
+                snapshot = new Dictionary<string, Dictionary<BackCompatibilityChangeCategory, SortedSet<string>>>(_bufferedMessages, StringComparer.Ordinal);
+                _bufferedMessages.Clear();


should we move this to the dispose?

Done in 221ab52 — removed the explicit WriteBufferedMessages() call from CSharpGen.ExecuteAsync. Dispose already flushes the buffer, so that's the single point where the summary is emitted now. --generated by Copilot

…to flush Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

github-actions · 2026-04-21T15:46:21Z

No changes needing a change description found.

Initial plan

9a2ef5c

Copilot AI assigned Copilot and jorgerangel-msft Apr 17, 2026

Copilot started work on behalf of jorgerangel-msft April 17, 2026 17:50 View session

Copilot AI linked an issue Apr 17, 2026 that may be closed by this pull request

Create Back Compatibility Changes Summary Logs #10414

Open

feat(http-client-csharp): add debug summary log for back-compatibilit…

49f220b

…y changes Agent-Logs-Url: https://github.com/microsoft/typespec/sessions/b2456212-73e8-4f37-b9e5-de37fa8f42d5 Co-authored-by: jorgerangel-msft <102122018+jorgerangel-msft@users.noreply.github.com>

microsoft-github-policy-service Bot added the emitter:client:csharp Issue for the C# client emitter: @typespec/http-client-csharp label Apr 17, 2026

address review feedback: stricter comparison and clearer category names

c8b2ce7

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Copilot AI changed the title ~~[WIP] Add debug level summary logs for back compatibility changes~~ Add debug-level summary log of back-compatibility changes in http-client-csharp generator Apr 17, 2026

Copilot AI requested a review from jorgerangel-msft April 17, 2026 18:08

Copilot finished work on behalf of jorgerangel-msft April 17, 2026 18:08

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Comment thread .chronus/changes/feature-back-compat-changes-summary-log-2026-4-17.md Outdated

Copilot started work on behalf of JoshLove-msft April 17, 2026 18:10 View session

revert changelog entry per review feedback

3418fc6

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Copilot finished work on behalf of JoshLove-msft April 17, 2026 18:13

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Comment thread ...nt-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/ClientProvider.cs Outdated

Copilot started work on behalf of JoshLove-msft April 17, 2026 18:14 View session

use enum for back-compat change categories

cb2c423

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Copilot finished work on behalf of JoshLove-msft April 17, 2026 18:19

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Comment thread ...lient-csharp/generator/Microsoft.TypeSpec.Generator/src/Utilities/BackCompatibilityLogger.cs Outdated

Copilot started work on behalf of JoshLove-msft April 17, 2026 19:29 View session

use plain "categories" in summary text to satisfy cspell

86bde11

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Copilot finished work on behalf of JoshLove-msft April 17, 2026 19:32

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JoshLove-msft marked this pull request as ready for review April 17, 2026 21:35

JoshLove-msft requested review from christothes and m-nash as code owners April 17, 2026 21:35

JoshLove-msft requested review from ShivangiReja, joseharriaga and jsquire as code owners April 17, 2026 21:35

jorgerangel-msft reviewed Apr 17, 2026

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Comment thread ...lient-csharp/generator/Microsoft.TypeSpec.Generator/src/Utilities/BackCompatibilityLogger.cs Outdated

Copilot started work on behalf of JoshLove-msft April 17, 2026 22:13 View session

refactor: integrate back-compat logging into Emitter pipeline

a92cc41

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Copilot finished work on behalf of JoshLove-msft April 17, 2026 22:28

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Comment thread ...ages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/EmitterRpc/LogCategory.cs Outdated

Copilot started work on behalf of JoshLove-msft April 17, 2026 23:04 View session

rename LogCategory back to BackCompatibilityChangeCategory

dbd3969

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address PR feedback: remove buffer snapshot copy and rely on Dispose …

221ab52

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jorgerangel-msft approved these changes Apr 22, 2026

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Add debug-level summary log of back-compatibility changes in http-client-csharp generator#10415

Add debug-level summary log of back-compatibility changes in http-client-csharp generator#10415
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