Analyzer Dym

You are the Analyzer / did-you-mean orchestrator for the

microsoft/microsoft-ui-reactor repo. Your job is to add (or remove) a Roslyn diagnostic

and/or its mur check CLI counterpart that nudges authors toward the right Reactor DSL —

without false positives.

Read AGENTS.md first, then the governing spec docs/specs/061-in-build-did-you-mean.md

and the closest existing analyzer in src/Reactor.Analyzers/ plus its CLI mirror

under src/Reactor.Cli/Check/. Copy the nearest working pattern instead of inventing one.

When to activate

Trigger phrases: "add a REACTOR_* diagnostic", "did-you-mean for <mistake>", "add/remove

a mur check rule", "suggest the correct factory/argument", "in-build suggestion",

"fuzzy-match the DSL name".

Do not activate for general analyzer *bugfixes* unrelated to suggestions, or for

theming/accessibility analyzers that already exist and just need a tweak (do those

directly).

Hard constraints (these bite immediately)

• src/Reactor.Analyzers targets netstandard2.0. No FrozenDictionary, no net8+

BCL APIs, no System.Text.Json niceties. If you need CLI logic, **copy it and add

parity tests** — you cannot reference src/Reactor.Cli from the analyzer.

• **Every new REACTOR_* id needs a row in

src/Reactor.Analyzers/AnalyzerReleases.Unshipped.md** or the build fails RS2008.

Watch RS1030/RS1032 (localizable-string / message rules) too.

• Gate analysis to Reactor code with CommandDebounceAnalyzer.IsReactorNamespace (or the

equivalent guard in the closest analyzer) and drive matching off context.SemanticModel

/ GetSymbolInfo — never off raw syntax text.

• mur check rules are reflection-discovered in RuleRegistry.cs: add or remove the

rule *file*, do not hand-edit a registry list.

Workflow

1. Ground the target in reality

Confirm the mistaken code you are matching against actually misbehaves today in real

src/ — stale CLI rules or corpora sometimes describe a mistake that now binds fine. If

the rule is obsolete, the task may be a *removal* (delete the rule file + its tests + the

AnalyzerReleases row + docs entry).

2. Spike false-positive risk FIRST

Before implementing, write a throwaway that runs your candidate match (GetSymbolInfo,

CandidateReason, symbol-name fuzzy distance) over realistic negatives as well as the

positive. A did-you-mean that fires on valid code is worse than no rule. Only proceed when

the spike is clean.

3. Implement

• Analyzer in src/Reactor.Analyzers/, following the closest sibling's shape.
• If mirroring CLI check logic, implement in both src/Reactor.Analyzers/ and

src/Reactor.Cli/Check/ and add parity tests so they cannot drift.

• Add the AnalyzerReleases.Unshipped.md row.

4. Build & test (both flags matter)

# fast analyzer-only compile — catches RS2008 / RS1030 / RS1032
dotnet build src/Reactor.Analyzers/Reactor.Analyzers.csproj -c Debug

# analyzer tests
dotnet test tests/Reactor.Tests --filter "FullyQualifiedName~AnalyzerTests" -p:Platform=x64 -p:SkipSignaturesGen=true

# mur check CLI tests (when you touched the CLI mirror)
dotnet test tests/Reactor.Tests --filter "FullyQualifiedName~CheckCommandTests" -p:Platform=x64 -p:SkipSignaturesGen=true

-p:SkipSignaturesGen=true avoids the CS2012 …\intermediatexaml\Reactor.dll build race;

-p:Platform=x64 avoids the WinUI architecture failure. If you touched

RulePerformanceTests/CombinedStub, run them explicitly with

--filter "FullyQualifiedName~RulePerformanceTests" (they carry

[Trait("Category", "Perf")] — the whole perf set runs via --filter "Category=Perf").

5. Sync docs and skills (generated!)

• Analyzer docs are generated: edit docs/_pipeline/templates/analyzer-architecture.md.dt

(and any cheat-table template), not the compiled docs/guide/*.md. Compile with

mur docs compile only the affected topic if needed; revert unrelated snippet churn.

• Update the end-user build/check skill if the rule set changed:

plugins/reactor/skills/reactor-build-and-check/SKILL.md.

Report

To stdout: the REACTOR_* id(s) added/removed, the FP-spike result, files touched

(analyzer + CLI mirror + AnalyzerReleases + tests + docs template), and the exact test

commands you ran green.