binlog-generation

# Generate Binary Logs ## Scope and routing Generate MSBuild binary logs (binlogs) for build diagnostics and analysis. USE FOR: adding /bl:{} to any dotnet build, test, pack, publish, or restore command to capture a full build execution trace, prerequisite for binlog-failure-analysis and build-perf-diagnostics skills, enabling post-build investigation of errors or performance. Requires MSBuild 17.8+ / .NET 8 SDK+ for {} placeholder; PowerShell must quote the complete switch as '-bl:{}'. DO NOT USE FOR: non-MSBuild build systems (npm, Maven, CMake), analyzing an existing binlog (use binlog-failure-analysis instead). **Pass the `/bl` switch when running any MSBuild-based command.** This is a non-negotiable requirement for all .NET builds. ## Commands That Require /bl You MUST add the `/bl:{}` flag to: - `dotnet build` - `dotnet test` - `dotnet pack` - `dotnet publish` - `dotnet restore` - `msbuild` or `msbuild.exe` - Any other command that invokes MSBuild ## Preferred: Use `{}` for Automatic Unique Names > **Note:** The `{}` placeholder requires MSBuild 17.8+ / .NET 8 SDK or later. The `{}` placeholder in the binlog filename is replaced by MSBuild with a unique identifier, guaranteeing no two builds ever overwrite each other — without needing to track or check existing files. ```bash # Every invocation produces a distinct file automatically dotnet build /bl:{} dotnet test /bl:{} dotnet build --configuration Release /bl:{} ``` **PowerShell requires quoting the complete switch:** ```powershell # Keep the literal {} placeholder in one argument dotnet build '-bl:{}' dotnet test '-bl:{}' ``` ## Why This Matters 1. **Unique names prevent overwrites** - You can always go back and analyze previous builds 2. **Failure analysis** - When a build fails, the binlog is already there for immediate analysis 3. **Comparison** - You can compare builds before and after changes 4. **No re-running builds** - You never need to re-run a failed build just to generate a binlog ## Examples ```bash # ✅ CORRECT - {} generates a unique name automatically (bash/cmd) dotnet build /bl:{} dotnet test /bl:{} # ✅ CORRECT - quote the complete PowerShell argument dotnet build '-bl:{}' dotnet test '-bl:{}' # ❌ WRONG - Missing /bl flag entirely dotnet build dotnet test # ❌ WRONG - No filename (overwrites the same msbuild.binlog every time) dotnet build /bl dotnet build /bl ``` ## One build = one binlog Add `/bl:{}` to **every** MSBuild invocation separately — never reuse a name and never rely on bare `/bl`: - Building several configurations, projects, or retrying a failed build? Each command still gets its own `/bl:{}` so the logs never overwrite each other. ```bash dotnet build -c Debug /bl:{} # unique file dotnet build -c Release /bl:{} # another unique file ``` ## Verify the binlog exists After the build, confirm a `.binlog` was actually produced before moving on to analysis — a build that fails *before* MSBuild starts (e.g. a bad argument) writes no binlog: ```bash ls -1 *.binlog # bash dir /b *.binlog # Windows cmd ``` ```powershell Get-ChildItem *.binlog # PowerShell ``` Note the resulting path so `binlog-failure-analysis` or `build-perf-diagnostics` can consume it. ## When a Specific Filename Is Required If the binlog filename needs to be known upfront (e.g., for CI artifact upload), or if `{}` is not available in the installed MSBuild version, pick a name that won't collide with existing files: 1. Check for existing `*.binlog` files in the directory 2. Choose a name not already taken (e.g., by incrementing a counter from the highest existing number) ```bash # Example: directory contains 3.binlog — use 4.binlog dotnet build /bl:4.binlog ``` ## Cleaning the Repository When cleaning the repository with `git clean`, **always exclude binlog files** to preserve your build history: ```bash # ✅ CORRECT - Exclude binlog files from cleaning git clean -fdx -e "*.binlog" # ❌ WRONG - This deletes binlog files (they're usually in .gitignore) git clean -fdx ``` This is especially important when iterating on build fixes - you need the binlogs to analyze what changed between builds.