perf(check-affected): keep the related run out of the unit projects on fail-open plans too

scripts/check-affected/run.test.ts

@@ -215,9 +215,10 @@ test('runChecks skips CI checks, runs every local check of a fail-open plan, and
   }
   const related = executed.filter((command) => command.includes('related'));
   assert.equal(related.length, 1);
-  assert.ok(
-    !related[0]?.some((arg) => arg.startsWith('--project')),
-    'a fail-open related run keeps every Vitest project',
+  // check:unit runs in this plan too, so the related run leaves the unit projects to it.
+  assert.deepEqual(
+    related[0]?.filter((arg) => arg.startsWith('--project')),
+    ['--project=!unit-core', '--project=!fuzz-worker'],
   );
   assert.ok(
     !related[0]?.includes('--coverage'),
@@ -251,6 +252,17 @@ test('runChecks skips CI checks, runs every local check of a fail-open plan, and
   );
 });
 
+// The related run leaves the unit projects out, so only check:unit can see their failures.
+test('a fail-open plan fails on a unit-suite failure', async () => {
+  const plan = selectChecks({ changedFiles: ['unknown/path.xyz'], packageEntryFiles: [] });
+  assert.equal(plan.failOpen, true);
+  const code = await runChecks(plan, { scripts: ALL_SCRIPTS }, ARGS, {
+    execute: async (command) => (command.includes('check:unit') ? 23 : 0),
+    cwd: '.',
+  });
+  assert.equal(code, 23);
+});
+
 async function runFailingOn(script: string, changedFiles: string[]): Promise<number> {
   const plan = selectChecks({ changedFiles, packageEntryFiles: [] });
   assert.equal(plan.failOpen, false, changedFiles.join(', '));

scripts/check-affected/run.ts

@@ -213,13 +213,13 @@ export async function runChecks(
   const skipped = plan.checks.map(getCheckSpec).filter((spec: CheckSpec) => !spec.localRunnable);
   // A fail-open plan could not narrow the change, so no check may stand in for another.
   const relatedSelected = !plan.failOpen && plan.checks.includes('vitest-related');
+  // Leaving the unit projects to `unit` stands in for nothing, so fail-open plans do it too.
+  // The run stops at the first failure, so no pass skips the `unit` run.
   const related = {
     changedFiles: options.changedFiles ?? [],
-    unitSuiteRuns:
-      !plan.failOpen &&
-      runnable.some(
-        (spec) => spec.id === 'unit' && !isCoveredByRelatedTests(spec, relatedSelected),
-      ),
+    unitSuiteRuns: runnable.some(
+      (spec) => spec.id === 'unit' && !isCoveredByRelatedTests(spec, relatedSelected),
+    ),
   };
   const ciJobs = skipped.length > 0 ? ciJobsByCheck() : new Map<CheckId, string[]>();
   for (const spec of skipped) {