fix(app): keep terminal mounted when switching session tabs in a workspace (#34852)

Co-authored-by: Brendan Allan <git@brendonovich.dev>

packages/app/test-browser/session-lineage.test.ts

@@ -0,0 +1,231 @@
+import { expect, test } from "bun:test"
+import { createRoot, createSignal } from "solid-js"
+import { createSessionLineage } from "@/pages/session/session-lineage"
+
+type Lineage = { session: { id: string; directory: string } }
+
+const lineageOf = (id: string): Lineage => ({ session: { id, directory: `/dir/${id}` } })
+
+// Fake sync lineage store: peek reads a reactive cache, resolve returns a
+// deferred promise the test settles or fails explicitly. The lineage memo is
+// live (read below), so it recomputes eagerly on cache/status writes — throws
+// surface at the write site, which is also where the enclosing ErrorBoundary
+// would see them in the app. Assertions wrap write + read to cover both.
+function createFixture(initial: Record<string, Lineage> = {}) {
+  const [cache, setCache] = createSignal(initial)
+  const deferred = new Map<string, PromiseWithResolvers<unknown>>()
+  const resolves: string[] = []
+  return {
+    resolves,
+    lineage: {
+      peek: (id: string) => cache()[id],
+      resolve: (id: string) => {
+        resolves.push(id)
+        const entry = deferred.get(id) ?? Promise.withResolvers<unknown>()
+        deferred.set(id, entry)
+        return entry.promise
+      },
+    },
+    settle(id: string) {
+      setCache({ ...cache(), [id]: lineageOf(id) })
+      deferred.get(id)?.resolve(undefined)
+    },
+    fail(id: string, error: unknown) {
+      deferred.get(id)?.reject(error)
+      // The real store does not cache failures: the inflight request entry is
+      // dropped on rejection so the next resolve retries (server-session.ts).
+      deferred.delete(id)
+    },
+    remove(id: string) {
+      const next = { ...cache() }
+      delete next[id]
+      setCache(next)
+    },
+  }
+}
+
+// Two microtask ticks: one for the resolve promise handed back by the fixture,
+// one for the .then/.catch chain inside createSessionLineage.
+const flush = async () => {
+  await Promise.resolve()
+  await Promise.resolve()
+}
+
+test("resolves an uncached session and exposes its lineage", async () => {
+  await createRoot(async (dispose) => {
+    const fixture = createFixture()
+    const current = createSessionLineage(
+      () => "ses_a",
+      () => fixture.lineage,
+    )
+
+    expect(current()).toBeUndefined()
+    await flush()
+    expect(fixture.resolves).toEqual(["ses_a"])
+
+    fixture.settle("ses_a")
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    dispose()
+  })
+})
+
+// Session tabs on the same server share one route instance, so navigating to
+// another session changes the id in place; resolution must follow it instead
+// of reporting the new session as missing.
+test("re-resolves when navigating to an uncached session without a remount", async () => {
+  await createRoot(async (dispose) => {
+    const fixture = createFixture({ ses_a: lineageOf("ses_a") })
+    const [id, setId] = createSignal("ses_a")
+    const current = createSessionLineage(id, () => fixture.lineage)
+
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    expect(() => {
+      setId("ses_b")
+      current()
+    }).not.toThrow()
+    expect(fixture.resolves).toEqual(["ses_b"])
+
+    fixture.settle("ses_b")
+    await flush()
+    expect(current()?.session.id).toBe("ses_b")
+
+    dispose()
+  })
+})
+
+// A late failure from a session the user already navigated away from must not
+// poison the currently viewed session.
+test("ignores a stale resolution failure after the target changes", async () => {
+  await createRoot(async (dispose) => {
+    const fixture = createFixture()
+    const [id, setId] = createSignal("ses_a")
+    const current = createSessionLineage(id, () => fixture.lineage)
+
+    await flush()
+    setId("ses_b")
+    fixture.fail("ses_a", new Error("Session not found: ses_a"))
+    await flush()
+
+    expect(() => current()).not.toThrow()
+    fixture.settle("ses_b")
+    await flush()
+    expect(current()?.session.id).toBe("ses_b")
+
+    dispose()
+  })
+})
+
+test("returning to a pruned session re-resolves instead of throwing not found", async () => {
+  await createRoot(async (dispose) => {
+    const fixture = createFixture()
+    const [id, setId] = createSignal("ses_a")
+    const current = createSessionLineage(id, () => fixture.lineage)
+
+    await flush()
+    fixture.settle("ses_a")
+    await flush()
+
+    setId("ses_b")
+    fixture.settle("ses_b")
+    await flush()
+
+    fixture.remove("ses_a")
+    expect(() => {
+      setId("ses_a")
+      current()
+    }).not.toThrow()
+    expect(fixture.resolves).toEqual(["ses_a", "ses_b", "ses_a"])
+
+    fixture.settle("ses_a")
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    dispose()
+  })
+})
+
+// A resolution that fails while its session is unfocused must not leave a
+// poisoned status behind: revisiting that session retries cleanly instead of
+// rethrowing the stale failure before the retry can start.
+test("revisiting a session whose resolution failed while unfocused retries cleanly", async () => {
+  await createRoot(async (dispose) => {
+    const fixture = createFixture()
+    const [id, setId] = createSignal("ses_a")
+    const current = createSessionLineage(id, () => fixture.lineage)
+
+    await flush()
+    setId("ses_b")
+    fixture.fail("ses_a", new Error("resolve failed"))
+    await flush()
+
+    expect(() => {
+      setId("ses_a")
+      current()
+    }).not.toThrow()
+    expect(fixture.resolves).toEqual(["ses_a", "ses_b", "ses_a"])
+
+    fixture.settle("ses_a")
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    dispose()
+  })
+})
+
+// The lineage accessor is reactive: replacing the sync store (for example after
+// the server context is rebuilt) must gate out the old store's status and
+// re-resolve against the new one instead of fabricating a not-found.
+test("re-resolves against a replaced lineage store", async () => {
+  await createRoot(async (dispose) => {
+    const first = createFixture()
+    const second = createFixture()
+    const [store, setStore] = createSignal(first.lineage)
+    const current = createSessionLineage(() => "ses_a", store)
+
+    await flush()
+    first.settle("ses_a")
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    expect(() => {
+      setStore(second.lineage)
+      current()
+    }).not.toThrow()
+    await flush()
+    expect(second.resolves).toEqual(["ses_a"])
+
+    second.settle("ses_a")
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    dispose()
+  })
+})
+
+// The viewed session is pinned in the cache, so disappearing after settlement
+// means it was deleted; the boundary must show the not found fallback.
+test("throws not found when the settled session is deleted", async () => {
+  await createRoot(async (dispose) => {
+    const fixture = createFixture()
+    const current = createSessionLineage(
+      () => "ses_a",
+      () => fixture.lineage,
+    )
+
+    await flush()
+    fixture.settle("ses_a")
+    await flush()
+    expect(current()?.session.id).toBe("ses_a")
+
+    expect(() => {
+      fixture.remove("ses_a")
+      current()
+    }).toThrow("Session not found: ses_a")
+
+    dispose()
+  })
+})