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 ", "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.
• Compare what a ModifierTable gate contains, not what it is called. The gate group names in ModifierTable.cs are their receiver lists concatenated, so a wider gate necessarily has a name containing the narrower one (ControlBorder ⊏ ControlBorderGridStack ⊏ …). Read ModifierInfo.ControlGate / PoolResetGate and compare type sets — prose gates name receiver types, so a doc-parity check compares sets too (see ModifierGateProseParityTests). Only when no typed property is reachable should you match the table as text, and then anchor it: SLOT:\s*NAME\s*[,)]. A bare Contains(NAME) passes on every wider gate, i.e. it silently green-lights exactly the mis-widening you were checking for. tests/Reactor.Tests/AnalyzerTests/ModifierGateSource.cs is the test-only reference implementation of that matcher — it is internal to Reactor.Tests, so a mur check rule cannot call it; copy the pattern and add a parity test, as with other analyzer/CLI shared logic.

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-class "*AnalyzerTests*" -p:Platform=x64 -p:SkipSignaturesGen=true

# mur check CLI tests (when you touched the CLI mirror)
dotnet test tests/Reactor.Tests --filter-class "*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-class "*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.