roslyn-mcp-pitfalls

Known pitfalls (do not reintroduce)

1. Relative paths vs CWD — Cursor often starts MCP with CWD = user home. Relative filePath without workspace resolve → wrong/missing files. Fix: ResolvePathAgainstWorkspace.

2. search_code without directory — scanning from home hangs forever. Default to loaded workspace directory; default extension filter .cs; add scan timeout.

3. get_code_skeleton vs decompile — agents pass assemblyName/typeName to file skeleton. Keep tools distinct; friendly error if path missing.

4. Fuzzy assembly match — Contains(name) picks wrong DLL. Exact {name}.dll + deps.json + NuGet/BCL fallback only.

5. SDK mismatch silent — 0 Error(s) while wrong MSBuild (9.x vs 10.x pin). Detect and emit MCP_MSBUILD_SDK_MISMATCH; fix env before app code.

6. NuGet audit invisible at -v:minimal — escalate restore/normal verbosity; parse embedded error NU####.

7. VSTest “partial” on missing counters — requiring both Passed: and Failed: is wrong. Success often omits Failed:; .slnx/MSBuild VSTest fail output often omits Passed:. Infer the missing side (Failed/Skipped → 0, or Passed = Total − Failed − Skipped). Total-only without those lines stays unparsed.

8. MSBuild bitness — 64-bit process + x86 SDK = BadImageFormat. Register matching MSBuild early.

9. CWD = BaseDirectory — publish folder breaks tools; use ROSLYN_MCP_WORKSPACE instead.

10. Hardcoded paths in docs — breaks other machines; resolve via IDE workspace / list_directory_tree.

11. run_specific_test filter — never put Roslyn FullyQualifiedFormat (method ()) into FullyQualifiedName=; VSTest treats () as grouping. Prefer FullyQualifiedName~ with Ns.Type.Method (no parens). Do not prefix a leading . when the needle is already dotted (.Ns.Class does not appear inside Ns.Class).

12. Fake/cached run_dotnet_build success — MCP has no result cache. False greens came from (a) MSBuild incremental/up-to-date skipping recompile → default --no-incremental; (b) probe lastExitCode overwritten by restore exit 0 after a failed build → effective exit = last build step only; (c) omitted -c on multi-config solutions. Always check metadata Configuration / NoIncremental.

13. Publish locked by zombie MCP — Cursor may keep RoslynMcpServer.exe running after MCP disconnect; publish then fails with MSB3027 file locks. publish-and-verify.ps1 auto-kills repo/publish holders (opt out: -SkipKill), then reload MCP.

14. apply_patch replaceAll hang — never rescan the inserted newString. If newString contains oldString (Foo → Ns.Foos), while (IndexOf) grows the buffer forever, MCP never returns, logs stay empty. Advance searchFrom past each insert (same as string.Replace); log start/match/write with newContainsOld and elapsed ms.

15. run_specific_test / run_dotnet_test without --no-build — a single dotnet test on a large .slnx dumps MSBuild warnings after (or instead of) the VSTest banner. Parser requires Passed! / Total tests: / Test Run Successful; exit 0 with only Time Elapsed / N Warning(s) becomes Status: partial + last 2KB of build footer. Split: dotnet build then dotnet test --no-build --no-restore; parse only the test process. Do not treat exit 0 as success and do not feed the build log to VstestOutputParser.

16. VSTest duration not only ms — slow tests print [1 s] / [1 m 28 s]. A Passed/Failed regex that requires ms only reports no matching tests despite Total tests: 1 / Passed: 1. Accept ms|s|m|h (compound durations). Do not treat any [...] as duration.

17. TargetFrameworks / missing Compile — Directory.Build.props with TargetFrameworks (even one TFM, or netstandard2.0;net10.0) makes design-time evaluation a CrossTargeting outer build: Build exists, Compile does not. load_workspace must pass targetFramework (inner TFM, e.g. net10.0). Do not treat this as SDK mismatch; dotnet build can still succeed. Dedicated failure lists TFMs from nearest props.