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authorWilliam Carroll <wpcarro@gmail.com>2022-06-21T19·49-0700
committerclbot <clbot@tvl.fyi>2022-06-27T18·28+0000
commitab1984c8ac07fea86d1779956fd4f9ebfbb91b9e (patch)
tree39ce1908c760eb82202eda78bf9d8942f615f6bc /users/wpcarro/website/blog/posts/csharp-unused-variables.md
parent46ba96544a8e13141d3f4920bc67e35dbdbc559f (diff)
feat(wpcarro/blog): Create short post about C# r/4263
Inspired by Profpatsch's "Notes", here's a short post about a thing that
happened today...

Note: I'd like a way to convert `git log --format=%b` into blog
posts (maybe). Maybe some commit metadata like `POST=true`

Change-Id: I492c48c81891d9f64da8c8149d0d2bfa864ed731
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5889
Tested-by: BuildkiteCI
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
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+# Unused Variables Broke Prod
+
+**Problem**: This morning we broke production because (believe it or not) an
+unused variable went undetected.
+
+**Solution**: Consume the variable in the relevant codepath.
+
+**Further AI**: Treat unused variables as errors (which will block CI).
+
+## Warning/Disclaimer
+
+I am not a C# programmer. I know close to nothing about C#. But at `$WORK`, one
+of our codebases is written in C#, so occasionally I interface with it.
+
+## Treating Unused Variables as Errors
+
+C# uses `.csproj` files to configure projects. The following changes to our
+`.csproj` file WAI'd:
+
+```diff
++    <!-- IDE0059: Remove unnecessary value assignment -->
++    <WarningsAsErrors>IDE0059</WarningsAsErrors>
++    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+```
+
+However, supporting this turned out to be a ~1h adventure... Why was this
+unexpectedly difficult? As it turns out, there are the 3x promising compiler
+warnings that I had to discover/try:
+
+- `CS0219`: doesn't WAI (see "Note" here: https://docs.microsoft.com/en-us/dotnet/csharp/misc/cs0219)
+- `CA1804`: silently unsupported (replaced by `IDE0059`)
+- `IDE0059`: WAIs
+
+Legend:
+- `CS`: stands for C#
+- `CA`: stands for Code Analysis (I *think* a Visual Studio concept)
+- `IDE`: stands for IDE (I think *also* a Visual Studio concept)
+
+For `CA` and `IDE` prefixed warnings, `EnforceCodeStyleInBuild` must also be
+enabled.