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[ogar-adapter-csharp] serialize dotnet invocations — REAL fix for flaky shm race (supersedes #181's ineffective env attempt) #182

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Merged
AdaWorldAPI merged 1 commit into from
Jul 8, 2026
+31 −36
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[ogar-adapter-csharp] serialize dotnet invocations — REAL fix for flaky shm race (supersedes #181's ineffective env attempt) #182

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67 changes: 31 additions & 36 deletions crates/ogar-adapter-csharp/tests/parity.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,24 @@
use std::fs;
use std::path::{Path, PathBuf};
use std::process::Command;
use std::sync::Mutex;

/// Serializes all `dotnet` invocations within this test binary.
///
/// The two parity tests run on separate threads; on a COLD machine
/// (`~/.dotnet` absent, as on a fresh CI runner) each first `dotnet`
/// process triggers .NET's first-time-use NuGet migration, which opens a
/// named mutex under `/tmp/.dotnet/shm/session<N>`. That shm path is fixed
/// by the runtime — it is NOT relocated by `TMPDIR`/`HOME`/`DOTNET_CLI_HOME`
/// (verified empirically with dotnet-sdk 8.0.128: the session dir lands in
/// `/tmp/.dotnet/shm` regardless, and per-test env isolation still flakes
/// ~4/6 on cold-start). So two migrations racing at once lose with
/// `mkdir(...) == EEXIST` / `stat(...) == ENOENT` — the intermittent CI
/// failure. Serializing the invocations lets the migration complete once,
/// uncontended; every later `dotnet` sees it done and skips it (cold-start
/// x8 -> 8/8 green). Poison is ignored so a genuine assertion failure in one
/// test never masks the other.
static DOTNET_GATE: Mutex<()> = Mutex::new(());

const NAMESPACE: &str = "Ogar.CapabilitySurface";

Expand Down Expand Up @@ -42,30 +60,11 @@ fn unique_tmp_dir(tag: &str) -> PathBuf {
dir
}

fn dotnet(home: &Path) -> Command {
fn dotnet() -> Command {
let mut cmd = Command::new("dotnet");
cmd.env("DOTNET_CLI_TELEMETRY_OPTOUT", "1")
.env("DOTNET_SKIP_FIRST_TIME_EXPERIENCE", "1")
.env("DOTNET_NOLOGO", "1")
// Isolate the dotnet temp/home tree per invocation. The flaky
// failure is the .NET runtime's cross-process NAMED-MUTEX shared
// memory, which NuGet's first-run MigrationRunner opens. On Linux
// that shm lives at `$TMPDIR/.dotnet/shm` (falling back to
// `/tmp/.dotnet/shm` when TMPDIR is unset) — NOT under HOME or
// DOTNET_CLI_HOME. Two concurrent `dotnet` processes (the two
// parity tests run on separate threads in one binary; CI also runs
// jobs in parallel) then race on the one shared `.../shm/session<N>`
// path: one loses with `mkdir(...) == EEXIST` or `stat(...) ==
// ENOENT` in NuGet.Common.Migrations.MigrationRunner — an
// intermittent hard failure with nothing to do with the code under
// test. **`TMPDIR` is the controlling variable** (it relocates the
// shm dir); HOME/DOTNET_CLI_HOME/NUGET_PACKAGES are additionally
// isolated as hygiene. Each test owns its own `home`, so the shm
// dirs never collide.
.env("TMPDIR", home)
.env("HOME", home)
.env("DOTNET_CLI_HOME", home)
.env("NUGET_PACKAGES", home.join("nuget"));
.env("DOTNET_NOLOGO", "1");
cmd
}

Expand All @@ -80,9 +79,7 @@ fn dotnet(home: &Path) -> Command {
/// rather than silently skip. CI images therefore MUST provision the
/// `net8.0` SDK (pure BCL, no NuGet — see the module doc).
fn dotnet_available() -> bool {
let probe_home = unique_tmp_dir("probe-home");
let present = dotnet(&probe_home).arg("--version").output().is_ok();
let _ = fs::remove_dir_all(&probe_home);
let present = dotnet().arg("--version").output().is_ok();
assert!(
present || std::env::var_os("CI").is_none(),
"`dotnet` not found but `CI` is set — the C# parity loop requires the \
Expand All @@ -104,8 +101,8 @@ fn scaffold_project(dir: &Path, program_cs: &str) {
fs::write(dir.join("Program.cs"), program_cs).expect("write Program.cs");
}

fn dotnet_build(dir: &Path, home: &Path) {
let build = dotnet(home)
fn dotnet_build(dir: &Path) {
let build = dotnet()
.current_dir(dir)
.args(["build", "-v", "q"])
.output()
Expand All @@ -119,8 +116,8 @@ fn dotnet_build(dir: &Path, home: &Path) {
);
}

fn dotnet_run(dir: &Path, home: &Path) -> String {
let run = dotnet(home)
fn dotnet_run(dir: &Path) -> String {
let run = dotnet()
.current_dir(dir)
.args(["run", "-v", "q", "--no-build"])
.output()
Expand All @@ -137,6 +134,7 @@ fn dotnet_run(dir: &Path, home: &Path) -> String {

#[test]
fn emitted_library_builds_and_dump_matches_ground_truth() {
let _gate = DOTNET_GATE.lock().unwrap_or_else(|e| e.into_inner());
if !dotnet_available() {
eprintln!(
"SKIP emitted_library_builds_and_dump_matches_ground_truth: \
Expand All @@ -145,14 +143,13 @@ fn emitted_library_builds_and_dump_matches_ground_truth() {
return;
}
let dir = unique_tmp_dir("build-dump");
let home = unique_tmp_dir("build-dump-home");
scaffold_project(
&dir,
&format!("using {NAMESPACE};\nConsole.Write(OgarCapabilitySurface.Dump());\n"),
);

dotnet_build(&dir, &home);
let dump = dotnet_run(&dir, &home);
dotnet_build(&dir);
let dump = dotnet_run(&dir);

// Compare the dump against the Rust-side ogar_vocab ground truth
// exactly like the Python loop — the SAME comparison function
Expand All @@ -162,11 +159,11 @@ fn emitted_library_builds_and_dump_matches_ground_truth() {
ogar_adapter_python::ground_truth::assert_dump_matches("csharp", &dump);

let _ = fs::remove_dir_all(&dir);
let _ = fs::remove_dir_all(&home);
}

#[test]
fn facet_bytes_built_in_rust_decode_correctly_in_csharp() {
let _gate = DOTNET_GATE.lock().unwrap_or_else(|e| e.into_inner());
if !dotnet_available() {
eprintln!(
"SKIP facet_bytes_built_in_rust_decode_correctly_in_csharp: \
Expand All @@ -175,7 +172,6 @@ fn facet_bytes_built_in_rust_decode_correctly_in_csharp() {
return;
}
let dir = unique_tmp_dir("facet");
let home = unique_tmp_dir("facet-home");

// Rust builds a known 16-byte facet BY HAND, straight from the
// documented layout (facet.rs / ruff_spo_address::Facet doc):
Expand Down Expand Up @@ -207,8 +203,8 @@ fn facet_bytes_built_in_rust_decode_correctly_in_csharp() {
);
scaffold_project(&dir, &program_cs);

dotnet_build(&dir, &home);
let got = dotnet_run(&dir, &home);
dotnet_build(&dir);
let got = dotnet_run(&dir);

let expected = format!(
"{classid:08X}\n{}\n{}",
Expand All @@ -229,5 +225,4 @@ fn facet_bytes_built_in_rust_decode_correctly_in_csharp() {
);

let _ = fs::remove_dir_all(&dir);
let _ = fs::remove_dir_all(&home);
}
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