refactor(mobile): pull request list records answers where they land

apps/mobile/src/features/pull-requests/pullRequestList.test.ts

@@ -13,12 +13,15 @@ import {
   mergeEnvironmentPullRequestPages,
   nextPullRequestListInput,
   PR_LIST_PAGE_SIZE,
+  patchPullRequestListEntry,
   pullRequestFilterChoices,
   pullRequestLabelColors,
   pullRequestListHead,
   pullRequestListInput,
   scopedPullRequestListKey,
+  shownPullRequestListPages,
   pullRequestListRowsAreEqual,
+  withShownPullRequestStats,
   withoutScratchProjectScope,
 } from "./pullRequestList";
 
@@ -115,6 +118,14 @@ describe("mobile PR list pagination", () => {
       mergePullRequestListEntries([entry(1)], [entry(2, { host: "enterprise.test" }), entry(2)]),
     ).toHaveLength(3);
   });
+  it("patches a row that only the list head supplies, and keeps it while that head is current", () => {
+    const head = page([entry(2), entry(1)], { repo: "first" });
+    const patched = patchPullRequestListEntry(null, head, entry(1), { state: "merged" }, 5);
+    expect(shownPullRequestListPages(patched, head)?.entries.map((row) => row.state)).toEqual([
+      "open",
+      "merged",
+    ]);
+  });
   it("refreshes the head without dropping older loaded pages or rewinding their cursor", () => {
     const first = pullRequestListHead(null, page([entry(3)], { repo: "first" }));
     const continued = appendPullRequestListPage(first, page([entry(2)], { repo: "second" }), {
@@ -387,3 +398,40 @@ describe("pullRequestFilterChoices", () => {
     expect(rows[50]).toBe("label-from-host");
   });
 });
+
+describe("shown PR diff stats", () => {
+  const cups = EnvironmentId.make("cups");
+  const stat = (number: number, additions: number, deletions: number) => ({
+    projectId: "project" as PullRequestListEntry["projectId"],
+    repository: "org/repo",
+    number,
+    additions,
+    deletions,
+  });
+  const rows = [
+    { ...entry(1), environmentId: cups },
+    { ...entry(2, { additions: 4, deletions: 1 }), environmentId: cups },
+  ];
+
+  it("keeps the same list when the answers change no row", () => {
+    expect(withShownPullRequestStats(rows, [])).toBe(rows);
+    expect(withShownPullRequestStats(rows, [{ environmentId: cups, stats: [stat(1, 0, 0)] }])).toBe(
+      rows,
+    );
+    expect(withShownPullRequestStats(rows, [{ environmentId: cups, stats: [stat(2, 9, 9)] }])).toBe(
+      rows,
+    );
+  });
+
+  it("fills only rows without stats, in their own environment", () => {
+    const filled = withShownPullRequestStats(rows, [
+      { environmentId: EnvironmentId.make("mbp"), stats: [stat(1, 7, 7)] },
+      { environmentId: cups, stats: [stat(1, 3, 2), stat(2, 9, 9)] },
+    ]);
+    expect(filled.map(({ additions, deletions }) => [additions, deletions])).toEqual([
+      [3, 2],
+      [4, 1],
+    ]);
+    expect(filled[1]).toBe(rows[1]);
+  });
+});

apps/mobile/src/features/pull-requests/pullRequestList.ts

@@ -3,6 +3,7 @@ import {
   ProjectId,
   resolvePullRequestAuthorFilter,
   type EnvironmentId,
+  type PullRequestDiffStat,
   type PullRequestListEntry,
   type PullRequestListInput,
   type PullRequestListResult,
@@ -45,6 +46,38 @@ export type EnvironmentPullRequestListEntry = PullRequestListEntry & {
 export const scopedPullRequestListKey = (entry: EnvironmentPullRequestListEntry) =>
   `${entry.environmentId}:${pullRequestListKey(entry)}`;
 
+export const pullRequestStatKey = (
+  row: Pick<PullRequestDiffStat, "projectId" | "repository" | "number">,
+) => `${row.projectId}:${row.repository}:${row.number}`;
+
+/**
+ * Fills rows that have no diff stat yet from the stats answers on screen. Returns `entries`
+ * itself when no row changes, so the list keeps its identity across renders.
+ */
+export function withShownPullRequestStats(
+  entries: readonly EnvironmentPullRequestListEntry[],
+  answers: readonly {
+    readonly environmentId: EnvironmentId;
+    readonly stats: readonly PullRequestDiffStat[];
+  }[],
+): readonly EnvironmentPullRequestListEntry[] {
+  const shown = new Map(
+    answers.flatMap(({ environmentId, stats }) =>
+      stats.map((row) => [`${environmentId}:${pullRequestStatKey(row)}`, row] as const),
+    ),
+  );
+  if (!shown.size) return entries;
+  let changed = false;
+  const next = entries.map((entry) => {
+    const stat = shown.get(`${entry.environmentId}:${pullRequestStatKey(entry)}`);
+    if (!stat || entry.additions + entry.deletions !== 0) return entry;
+    if (stat.additions + stat.deletions === 0) return entry;
+    changed = true;
+    return { ...entry, additions: stat.additions, deletions: stat.deletions };
+  });
+  return changed ? next : entries;
+}
+
 export function pullRequestListRowsAreEqual(
   previous: EnvironmentPullRequestListEntry,
   next: EnvironmentPullRequestListEntry,
@@ -143,6 +176,34 @@ export function pullRequestListHead(
       };
 }
 
+/** The recorded pages with the current list head on top; before any answer is recorded, the head alone. */
+export function shownPullRequestListPages(
+  recorded: PullRequestListPages | null,
+  head: PullRequestListResult | null,
+): PullRequestListPages | null {
+  return head ? pullRequestListHead(recorded, head) : recorded;
+}
+
+export function patchPullRequestListEntry(
+  recorded: PullRequestListPages | null,
+  head: PullRequestListResult | null,
+  entry: PullRequestListEntry,
+  patch: Partial<PullRequestListEntry>,
+  observedAt: number,
+): PullRequestListPages | null {
+  const pages = shownPullRequestListPages(recorded, head);
+  return (
+    pages && {
+      ...pages,
+      entries: pages.entries.map((row) =>
+        pullRequestListKey(row) === pullRequestListKey(entry)
+          ? { ...row, ...patch, observedAt }
+          : row,
+      ),
+    }
+  );
+}
+
 export function pullRequestListInput(
   controls: PullRequestListControls,
   query: string,