NuGet crawler test crawls the host's ~/.nuget/packages and fails on dev machines #2023

LLM Description written by Claude Code:claude-opus-5-5

Summary

crawlers::nuget_crawler::tests::solution_roots_and_unrestored_projects_keep_the_walk (crates/socket-patch-core/src/crawlers/nuget_crawler.rs:1978) is not hermetic. It crawls the real global packages folder of the machine running it, so it fails on any developer machine whose ~/.nuget/packages holds a package. It passes in CI only because the runners' NuGet cache is empty.

Repro

On main (7bde3ba), on a machine with any package in ~/.nuget/packages:

cargo test --locked -p socket-patch-core --lib solution_roots_and_unrestored_projects_keep_the_walk

panicked at crates/socket-patch-core/src/crawlers/nuget_crawler.rs:1994:9:
  left: ["pkg:nuget/newtonsoft.json@12.0.1", "pkg:nuget/newtonsoft.json@13.0.3", "pkg:nuget/serilog@3.1.1", "pkg:nuget/socketsecurity.socketpatch@3.3.0"]
 right: ["pkg:nuget/newtonsoft.json@12.0.1", "pkg:nuget/newtonsoft.json@13.0.3", "pkg:nuget/serilog@3.1.1"]

The extra purl comes from the host's ~/.nuget/packages/socketsecurity.socketpatch/3.3.0. The test fails every time on such a machine, and passes with an isolated home:

HOME=$(mktemp -d) CARGO_HOME=~/.cargo RUSTUP_HOME=~/.rustup \
  cargo test --locked -p socket-patch-core --lib solution_roots_and_unrestored_projects_keep_the_walk
# test result: ok. 1 passed

Root cause

In project mode, crawl_roots always adds the global packages folder NuGet would restore into as search root 3 (nuget_crawler.rs:626-630, via global_packages_folder → nuget_home(), which falls back to $DOTNET_CLI_HOME or ~/.nuget/packages). A solution root, or a project that hasn't been restored, has no restore scope (roots.scope is set only for DotnetRoot::Project), so every package in that folder is crawled.

The test builds its packages in a temp shared-cache named by packageFolders, but leaves NUGET_PACKAGES and DOTNET_CLI_HOME unset. Its expected list (every) therefore assumes the host's default folder is empty or missing.

Suggested fix

Run the crawl under the existing crate::test_env::EnvGuard, with NUGET_PACKAGES pointed at an empty directory inside the test's tempdir (and DOTNET_CLI_HOME cleared). That makes root 3 hermetic without changing the crawler.

The NUGET_PACKAGES test around nuget_crawler.rs:1450 sets and removes the variable with bare std::env::set_var/remove_var, outside the guard. It should move onto EnvGuard too, so a parallel crawl test can't observe the variable while it's set.

Note

The product behavior the test pins, where a solution-root or unrestored-project crawl includes every package in the user's global folder, is the unscoped "today's walk" that #427 / #1183 deliberately kept for those roots. This issue is only about the test's isolation.

Found while validating #2015.