Cut the CI build time: analyzers once per project, cache NuGet

.github/actions/run-tests/action.yml

@@ -57,6 +57,14 @@ runs:
           8.0.x
           10.0.x
 
+    # Restore is ~80s of the build step on a cold runner, and the package set changes rarely.
+    - name: Cache NuGet packages
+      uses: actions/cache@v4
+      with:
+        path: ~/.nuget/packages
+        key: ${{ runner.os }}-nuget-${{ hashFiles('Directory.Packages.props', 'global.json', '**/*.csproj') }}
+        restore-keys: ${{ runner.os }}-nuget-
+
     - name: .NET Build
       shell: bash
       run: dotnet build Build.csproj -c Release /p:CI=true
@@ -65,6 +73,7 @@ runs:
       shell: bash
       run: >-
         dotnet test tests/StackExchange.Redis.Tests/StackExchange.Redis.Tests.csproj
+        --no-build
         -c Release
         -f net10.0
         --logger trx

.github/workflows/CI.yml

@@ -128,6 +128,13 @@ jobs:
           redis-cli -p 26381 INFO SERVER | grep redis_version || echo "Failed to get version for port 26381"
         continue-on-error: true
 
+      # Restore is ~80s of the build step on a cold runner, and the package set changes rarely.
+      - name: Cache NuGet packages
+        uses: actions/cache@v4
+        with:
+          path: ~/.nuget/packages
+          key: ${{ runner.os }}-nuget-${{ hashFiles('Directory.Packages.props', 'global.json', '**/*.csproj') }}
+          restore-keys: ${{ runner.os }}-nuget-
       - name: .NET Build
         run: dotnet build Build.csproj -c Release /p:CI=true
       # The analyzer and the props that configures it reach consumers only through the package, and a
@@ -156,7 +163,7 @@ jobs:
         run: |
           $exitCode = 0
           foreach ($tfm in @("net10.0", "net481")) {
-            dotnet test tests/StackExchange.Redis.Tests/StackExchange.Redis.Tests.csproj -c Release -f $tfm --logger trx --logger GitHubActions --results-directory ./test-results/ /p:CI=true
+            dotnet test tests/StackExchange.Redis.Tests/StackExchange.Redis.Tests.csproj --no-build -c Release -f $tfm --logger trx --logger GitHubActions --results-directory ./test-results/ /p:CI=true
             if ($LASTEXITCODE -ne 0) {
               $exitCode = $LASTEXITCODE
             }

AGENTS.md

@@ -41,6 +41,7 @@ dotnet pack src/StackExchange.Redis/StackExchange.Redis.csproj --no-build -c Rel
 
 - SDK is pinned (`global.json`, `allowPrerelease: false`); CI installs the 6/8/10 runtimes. `LangVersion` is 14.
 - `TreatWarningsAsErrors=true` everywhere and `Features=strict` — warnings fail the build. Analyzers (StyleCop + the custom `eng` analyzer + PublicApiAnalyzers) run as part of the build.
+- Analyzers run on **one TFM per project** — the newest it builds (see `Directory.Build.targets`), because they cost ~40% of a clean build otherwise and every rule is TFM-agnostic. Source generators still run on every TFM. If you touch code inside a down-level `#if`, build it with `/p:RunAnalyzers=true` to get the full per-TFM sweep. StyleCop applies to `src/` only, not `tests/` or `toys/`.
 - Library multi-targets `net461;netstandard2.0;net472;net6.0;net8.0;net10.0`. Conditional compile symbols: `VECTOR_SAFE` (all but net461), `UNIX_SOCKET` (net6.0+). The test project targets `net481;net8.0;net10.0`; `BUILD_CURRENT` is defined on the newest TFM (disables some parallelism for brittle tests).
 
 ## Public API tracking (important — easy to trip over)
@@ -113,6 +114,6 @@ Be consise and direct where possible, but with as much detail as is necessary; n
 
 ## Conventions
 
-- Code style is enforced via `.editorconfig` + `Shared.ruleset` + StyleCop; 4-space indent, BOM + final newline on `.cs`, `System.*` usings first, no redundant `this.`. Build will fail on violations.
+- Code style is enforced via `.editorconfig` + `Shared.ruleset` + StyleCop (StyleCop in `src/` only); 4-space indent, BOM + final newline on `.cs`, `System.*` usings first, no redundant `this.`. Build will fail on violations. Match the surrounding style in `tests/`/`toys/` too — the rules are simply not enforced there.
 - `InternalsVisibleTo` exposes internals to the test/benchmark/server projects, so tests reach into internal types directly.
 - `docs/` markdown is the user-facing documentation; update it for user-visible behavior changes.

Directory.Build.props

@@ -42,7 +42,6 @@
 
   <ItemGroup Condition="'$(MSBuildProjectName)' != 'StackExchange.Redis.Build' and '$(MSBuildProjectName)' != 'docker' and '$(MSBuildProjectName)' != 'docs' and '$(MSBuildProjectName)' != '.github'">
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" PrivateAssets="all" />
-    <PackageReference Include="StyleCop.Analyzers" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(MSBuildProjectName)' != 'Build' and '$(MSBuildProjectName)' != 'StackExchange.Redis.Build' and '$(MSBuildProjectName)' != 'docker' and '$(MSBuildProjectName)' != 'docs' and '$(MSBuildProjectName)' != '.github'">

Directory.Build.targets

@@ -2,4 +2,30 @@
   <ItemGroup>
     <EmbeddedFiles Include="$(GeneratedAssemblyInfoFile)"/>
   </ItemGroup>
-</Project>
+
+  <!--
+    Analyzers are around 40% of a clean build's wall time, and every rule we run is TFM-agnostic: the same
+    file is analysed once per TargetFramework, so a six-TFM library pays for the same diagnostics six times.
+    Run them on one TFM per project instead - the newest the project builds, which is the branch of any #if
+    with the most code behind it. Source generators are unaffected: RunAnalyzers=false only suppresses
+    DiagnosticAnalyzers, so the generated code is identical on every TFM.
+
+    What this gives up: a diagnostic that only fires in down-level conditional code, and (for
+    PublicApiAnalyzers) public API that exists *only* on an older TFM. Pass /p:RunAnalyzers=true to get the
+    full per-TFM sweep back - worth doing after touching code inside a down-level #if.
+
+    Note this lives in .targets, not .props: TargetFrameworks is only known once the project body has been
+    evaluated. Single-TFM projects leave TargetFrameworks empty and are untouched.
+  -->
+  <PropertyGroup Condition="'$(RunAnalyzers)' == '' and '$(TargetFramework)' != '' and '$(TargetFrameworks)' != ''">
+    <!-- first match wins, so this list is newest-first rather than a sort we cannot express in MSBuild -->
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('net10.0'))">net10.0</_AnalyzedTargetFramework>
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('net8.0'))">net8.0</_AnalyzedTargetFramework>
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('net6.0'))">net6.0</_AnalyzedTargetFramework>
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('netstandard2.0'))">netstandard2.0</_AnalyzedTargetFramework>
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('net481'))">net481</_AnalyzedTargetFramework>
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('net472'))">net472</_AnalyzedTargetFramework>
+    <_AnalyzedTargetFramework Condition="'$(_AnalyzedTargetFramework)' == '' and $(TargetFrameworks.Contains('net461'))">net461</_AnalyzedTargetFramework>
+    <RunAnalyzers Condition="'$(_AnalyzedTargetFramework)' != '' and '$(TargetFramework)' != '$(_AnalyzedTargetFramework)'">false</RunAnalyzers>
+  </PropertyGroup>
+</Project>

src/Directory.Build.props

@@ -8,6 +8,10 @@
     <PackageIcon>seredis.png</PackageIcon>
   </PropertyGroup>
   <ItemGroup>
+    <!-- The shipped code only. StyleCop is by far the most expensive analyzer we run (two thirds of all
+         analyzer time in a clean build), and it was buying nothing in tests/ and toys/ that review does not:
+         those are not part of the published surface and have no docs requirements. -->
+    <PackageReference Include="StyleCop.Analyzers" PrivateAssets="All" />
     <PackageReference Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" PrivateAssets="all" />
     <PackageReference Include="Nerdbank.GitVersioning" PrivateAssets="all" Condition=" '$(DEVCONTAINER)' != 'true' " />

src/RESPite.Benchmark/RESPite.Benchmark.csproj

@@ -8,7 +8,8 @@
     <ToolCommandName>resp-benchmark</ToolCommandName>
     <PackAsTool>true</PackAsTool>
     <Title>command-line "RESP" benchmark client, comparable to redis-benchmark</Title>
-    <GeneratePackageOnBuild Condition="'$(Configuration)'=='Release'">True</GeneratePackageOnBuild>
+    <!-- no GeneratePackageOnBuild: that packed a nupkg on every Release build (including all of CI, for
+         nobody's benefit). The tool is still published - the pack step packs Build.csproj, which includes us. -->
     <PackageReadmeFile>readme.md</PackageReadmeFile>
     <GenerateDocumentationFile>False</GenerateDocumentationFile>
     <WarningsAsErrors Condition="'$(Configuration)'=='Debug'">false</WarningsAsErrors>