fix(observability-map): keep the test task out of the turbo cache

The suite scans apps/webapp/app, packages/plugins/src, internal-packages/rbac/src
and four files under .github/workflows, none of which turbo hashes for this
package, so turbo run test replayed a pass recorded before those trees changed.
Measured rather than argued: a route file with a syntax error fails the suite
under vitest, and the same tree came back FULL TURBO in 301ms with the failure
cached away as a success.

inputs was tried and rejected rather than assumed unworkable. Turbo 1.x does
accept .. in an input glob, and ../../apps/webapp/app/** did bust the cache on a
route change, but it replaces the default file set instead of adding to it, so
the same config silently dropped this package's own vitest.config.ts from the
hash. The $TURBO_DEFAULT$ token that would add rather than replace is turbo 2.x
only and matches nothing on 1.10.3.

Costs about 23s per run and no CI job pays it: the dedicated workflow calls
vitest without turbo, and unit-tests-internal.yml runs cold.

Reported by Devin on #4455.

Author: 1stvamp

internal-packages/observability-map/src/integration.test.ts

@@ -213,6 +213,37 @@ describe("the package's tests are wired into the gate", () => {
   });
 });
 
+/**
+ * The third road into this suite, after the two workflows above: `turbo run test`, which is what
+ * `pnpm run test` and `pnpm run test:internal` reach it by.
+ *
+ * Turbo keys a task's cache on the package's own files. This suite's real inputs are mostly not
+ * its own files, they are `apps/webapp/app`, `packages/plugins/src`, `internal-packages/rbac/src`
+ * and the workflow files read above, so turbo happily replayed a pass recorded before a route
+ * changed. Measured rather than argued: a route file with a syntax error in it makes
+ * `parses every route file and produces a report inside a wide band` fail under vitest, and the
+ * same tree came back FULL TURBO in 301ms with the failure cached away as a success.
+ *
+ * So the task is uncacheable, and this asserts that, because the config is one line and reads like
+ * a performance oversight to anyone who does not know what the suite reads.
+ *
+ * What this does not assert is the rejected alternative. `inputs` can name `../../apps/webapp/...`
+ * and does bust the cache, but it replaces turbo 1.x's default file set instead of adding to it,
+ * so it drops the package's own files from the hash unless every one of them is listed too; that
+ * was measured the same way, by editing `vitest.config.ts` and getting FULL TURBO back. The
+ * reasoning lives in `turbo.json` next to the config it explains.
+ */
+describe("the third road in, turbo", () => {
+  it("keeps its test task out of the turbo cache", () => {
+    const config = readFileSync(resolve(__dirname, "../turbo.json"), "utf8");
+    // Comments are legal in turbo.json and this one carries the reasoning, so strip them to parse.
+    const pipeline = JSON.parse(config.replace(/^\s*\/\/.*$/gm, "")) as {
+      pipeline?: { test?: { cache?: boolean } };
+    };
+    expect(pipeline.pipeline?.test?.cache).toBe(false);
+  });
+});
+
 describe("counting candidates independently of the scanner", () => {
   // The counter is only worth having if it disagrees with the scanner somewhere. It does: the
   // scanner attributes nothing to a nested file that is not `route.ts`/`route.tsx`, and the

internal-packages/observability-map/turbo.json

@@ -0,0 +1,31 @@
+{
+  "$schema": "https://turborepo.org/schema.json",
+  "extends": ["//"],
+  "pipeline": {
+    // Uncacheable on purpose. This suite's real inputs live outside the package: it scans
+    // `apps/webapp/app`, `packages/plugins/src`, `internal-packages/rbac/src` and four files under
+    // `.github/workflows`. The root `test` task keys the cache on this package's own files, so a
+    // cached pass replayed after a route change broke the scan, which is a guard that stops
+    // guarding while still reading green.
+    //
+    // `inputs` was tried and rejected rather than assumed unworkable. Turbo 1.x does accept `..`
+    // in an input glob, and `../../apps/webapp/app/**` did bust the cache on a route change. What
+    // it also does is replace the default file set rather than add to it, so the same config
+    // silently dropped this package's own `vitest.config.ts` from the hash: editing it replayed a
+    // cached pass. The `$TURBO_DEFAULT$` token that adds rather than replaces is turbo 2.x only
+    // and matches nothing on the 1.10.3 here. Trading a stale-on-routes hole for a
+    // stale-on-own-config hole is not a fix, and an inputs list mirroring what the tests read is
+    // one more thing that drifts out of sync without saying so.
+    //
+    // Cost is about 23s per run, and no CI job pays it: the dedicated workflow calls vitest
+    // without turbo, and `unit-tests-internal.yml` runs cold.
+    //
+    // `it("keeps its test task out of the turbo cache")` in `src/integration.test.ts` fails if
+    // this is removed.
+    "test": {
+      "dependsOn": ["^build"],
+      "outputs": [],
+      "cache": false
+    }
+  }
+}