src/App.vue

@@ -11,7 +11,7 @@ import { layout } from "./lib/layout";
 import { textWidth } from "./lib/measure";
 import { colorOf } from "./lib/palette";
 import { addRecent, mergeRecents } from "./lib/recents";
-import { tickets } from "./lib/latest";
+import { repoRequests, type Request } from "./lib/latest";
 import type { FileDiff, Layout } from "./lib/diff";
 import type { ChangedFile, CommitDetails, FilterState, Ref, RefKind, RepoData } from "./lib/types";
 import DiffView from "./components/DiffView.vue";
@@ -107,10 +107,10 @@ let filtersLoadedFor: string | null = null;
 let loading = false;
 /**
  * Git runs away from the window, so replies can arrive in another order than the requests
- * went out. Every request that can put a new repository on screen (a reload or opening one)
- * takes a ticket; a reply is used only if no newer such request was sent after it.
+ * went out. Every reload and every open is noted here, and its reply is used only if
+ * `requests.isCurrent` allows it: opening a repository wins over a reload.
  */
-const repoRequests = tickets();
+const requests = repoRequests();
 /** False until the first load answers, so the welcome screen does not flash up at start. */
 const started = ref(false);
 
@@ -118,14 +118,14 @@ async function load() {
   // The window gets focus often; one reload at a time is enough.
   if (loading) return;
   loading = true;
-  const ticket = repoRequests.take();
+  const request = requests.startReload();
   try {
     // null: gites was started outside a repository and none is open yet.
     const data = await invoke<RepoData | null>("load_repo");
-    if (data) await applyRepo(data, ticket);
+    if (data) await applyRepo(data, request);
   } catch (e) {
-    // A newer request replaced this one; its error no longer matters.
-    if (!repoRequests.isLatest(ticket)) return;
+    // An open replaced this reload; its error no longer matters.
+    if (!requests.isCurrent(request)) return;
     // A repository already on screen stays, for example when a connection drops.
     if (repo.value) showToast(`could not reload: ${e}`, { error: true });
     else error.value = String(e);
@@ -137,14 +137,16 @@ async function load() {
 
 async function openRepo(path: string) {
   menuOpen.value = false;
-  const ticket = repoRequests.take();
+  const request = requests.startOpen();
   try {
-    await applyRepo(await invoke<RepoData>("open_repo", { path }), ticket);
+    await applyRepo(await invoke<RepoData>("open_repo", { path }), request);
   } catch (e) {
-    // A newer request replaced this one; its error no longer matters.
-    if (!repoRequests.isLatest(ticket)) return;
+    // A newer open replaced this one; its error no longer matters.
+    if (!requests.isCurrent(request)) return;
     // The repository that was open stays open.
     showToast(`could not open ${path}: ${e}`, { error: true });
+  } finally {
+    requests.finish(request);
   }
 }
 
@@ -157,16 +159,16 @@ async function browse() {
 
 const menuOpen = ref(false);
 
-/** Puts `data` on screen, unless a request newer than the one holding `ticket` was sent. */
-async function applyRepo(data: RepoData, ticket: number) {
-  if (!repoRequests.isLatest(ticket)) return;
+/** Puts `data` on screen, unless `request` was replaced (see `requests`). */
+async function applyRepo(data: RepoData, request: Request) {
+  if (!requests.isCurrent(request)) return;
   error.value = null;
   if (filtersLoadedFor !== data.root) {
     const saved = await invoke<Partial<FilterState & { collapseAll: boolean }> | null>("load_filters", {
       repo: data.root,
     });
     // Another repository may have been asked for while the filters were read.
-    if (!repoRequests.isLatest(ticket)) return;
+    if (!requests.isCurrent(request)) return;
     filters.hidden = saved?.hidden ?? [];
     filters.rules = saved?.rules ?? [];
     filters.hideTags = saved?.hideTags ?? false;

src/lib/latest.test.ts

@@ -1,33 +1,57 @@
 import { describe, expect, it } from "vitest";
-import { tickets } from "./latest";
+import { repoRequests } from "./latest";
 
-describe("tickets", () => {
-  it("treats the only ticket taken as the newest", () => {
-    const t = tickets();
-    const a = t.take();
-    expect(t.isLatest(a)).toBe(true);
+describe("repoRequests", () => {
+  it("applies a reload with no open around", () => {
+    const r = repoRequests();
+    const reload = r.startReload();
+    expect(r.isCurrent(reload)).toBe(true);
   });
-  it("treats an older ticket as out of date once a newer one is taken", () => {
-    const t = tickets();
-    const older = t.take();
-    const newer = t.take();
-    expect(t.isLatest(older)).toBe(false);
-    expect(t.isLatest(newer)).toBe(true);
+  it("applies a reload that starts after an open has finished", () => {
+    const r = repoRequests();
+    const open = r.startOpen();
+    r.finish(open);
+    const reload = r.startReload();
+    expect(r.isCurrent(reload)).toBe(true);
   });
-  it("keeps an older ticket out of date after more tickets are taken", () => {
-    const t = tickets();
-    const first = t.take();
-    t.take();
-    const last = t.take();
-    expect(t.isLatest(first)).toBe(false);
-    expect(t.isLatest(last)).toBe(true);
+  it("drops a reload started during a running open, and applies the open", () => {
+    const r = repoRequests();
+    const open = r.startOpen();
+    const reload = r.startReload();
+    // The reload answers first, while the open is still running.
+    expect(r.isCurrent(reload)).toBe(false);
+    expect(r.isCurrent(open)).toBe(true);
+    r.finish(open);
+    // Its reply may hold the repository from before the open, so it stays dropped.
+    expect(r.isCurrent(reload)).toBe(false);
   });
-  it("keeps separate sets of tickets apart", () => {
-    const a = tickets();
-    const b = tickets();
-    const fromA = a.take();
-    b.take();
-    b.take();
-    expect(a.isLatest(fromA)).toBe(true);
+  it("drops a reload when an open starts after it", () => {
+    const r = repoRequests();
+    const reload = r.startReload();
+    const open = r.startOpen();
+    expect(r.isCurrent(reload)).toBe(false);
+    r.finish(open);
+    expect(r.isCurrent(reload)).toBe(false);
+    expect(r.isCurrent(open)).toBe(true);
+  });
+  it("applies only the newer of two opens", () => {
+    const r = repoRequests();
+    const older = r.startOpen();
+    const newer = r.startOpen();
+    expect(r.isCurrent(older)).toBe(false);
+    expect(r.isCurrent(newer)).toBe(true);
+  });
+  it("applies an open even when a reload started after it", () => {
+    const r = repoRequests();
+    const open = r.startOpen();
+    r.startReload();
+    expect(r.isCurrent(open)).toBe(true);
+  });
+  it("keeps separate sets of requests apart", () => {
+    const a = repoRequests();
+    const b = repoRequests();
+    const reload = a.startReload();
+    b.startOpen();
+    expect(a.isCurrent(reload)).toBe(true);
   });
 });

src/lib/latest.ts

@@ -1,17 +1,41 @@
 /**
- * Numbers requests so that only the reply to the newest one is used. Take a ticket before
- * sending a request; when its reply arrives, use it only if `isLatest` says no newer ticket
- * was taken in the meantime.
+ * Decides which replies may put a repository on screen. Git runs away from the window, so
+ * replies can arrive in another order than the requests went out. Opening a repository wins
+ * over a reload:
+ * - a reload's reply is dropped if an open was running when the reload started, if an open
+ *   started after it, or if an open is still running when the reply arrives;
+ * - an open's reply is dropped only if a newer open started after it.
  */
-export interface Tickets {
-  take(): number;
-  isLatest(ticket: number): boolean;
+export type Request = { kind: "open" | "reload"; number: number; duringOpen: boolean };
+
+export interface RepoRequests {
+  startOpen(): Request;
+  startReload(): Request;
+  /** Call when an open has finished, whether its reply was used or not. */
+  finish(request: Request): void;
+  isCurrent(request: Request): boolean;
 }
 
-export function tickets(): Tickets {
-  let newest = 0;
+export function repoRequests(): RepoRequests {
+  let counter = 0;
+  let newestOpen = 0;
+  const runningOpens = new Set<number>();
   return {
-    take: () => ++newest,
-    isLatest: (ticket) => ticket === newest,
+    startOpen() {
+      const number = ++counter;
+      newestOpen = number;
+      runningOpens.add(number);
+      return { kind: "open", number, duringOpen: false };
+    },
+    startReload() {
+      return { kind: "reload", number: ++counter, duringOpen: runningOpens.size > 0 };
+    },
+    finish(request) {
+      runningOpens.delete(request.number);
+    },
+    isCurrent(request) {
+      if (request.kind === "open") return request.number === newestOpen;
+      return !request.duringOpen && newestOpen < request.number && runningOpens.size === 0;
+    },
   };
 }