fix(folio): attribute a created account by its whole key, not a suffix

createdAccountHasNonZeroBalance matched the created card with endsWith, so
an older account whose name ends with the typed one ("Emergency Fund" for a
typed "Fund") was judged instead whenever the new card was clipped out of
the reading. Build both keys the card can carry, the plain name and web's
initials + name, and compare them whole.

examples/folio/sanderling/predicates.ts

@@ -259,6 +259,24 @@ export function cardAccountName(args: {
   return head.slice(0, label.index).trim();
 }
 
+// The avatar text that opens a merged card's identity key, mirroring Folio's
+// initialsOf (app/shared/.../util/Format.kt).
+//
+// A mirror because the alternative is a suffix test, and a suffix test cannot
+// say which card a name belongs to. Drift can only cost a detection: the result
+// is compared whole against a card's key, so initials that stop matching the
+// app match no card rather than the wrong one.
+export function initialsOf(name: string): string {
+  // Java's \s, which is what Kotlin's Regex("\\s+") compiles to. JS's \s also
+  // matches the unicode spaces, and would split names the app keeps whole.
+  const parts = name.trim().split(/[ \t\n\v\f\r]+/).filter(part => part !== "");
+  const first = parts[0];
+  const last = parts[parts.length - 1];
+  if (first === undefined || last === undefined) return "?";
+  if (parts.length === 1) return first.slice(0, 2).toUpperCase();
+  return (first.slice(0, 1) + last.slice(0, 1)).toUpperCase();
+}
+
 // One card's transaction count, in the strongest form its SOURCE supports. The
 // two forms are the whole reason this is not just a number:
 //
@@ -386,10 +404,21 @@ export function createdAccountHasNonZeroBalance(args: {
   if (typed === "") return false;
   // Web merges the card into one node whose text opens with the avatar
   // initials, so the identity key is "INInvestments" where android and iOS give
-  // "Investments"; endsWith covers both. Two cards answering to the same typed
+  // "Investments". Both forms are built from the name that was typed and
-  // name (a second "Travel", or a card the tree exposed twice) leave the
+  // compared whole. A suffix test covered both too, and it also let any OTHER
-  // appearance unattributable, so nothing is judged.
+  // account ending in those letters answer for the created one: type "Fund"
-  const matches = after.filter(account => account.name.endsWith(typed));
+  // next to an existing "Emergency Fund", have the new card clipped out of the
+  // reading the way Home clips any card, and the old account is convicted for
+  // money it has held all along. It cost detections as well, because a typed
+  // name that two cards end with is judged as unattributable rather than as the
+  // one card that carries it.
+  //
+  // Two cards answering to one key stay unattributable: Accounts.name is UNIQUE
+  // and Repository.createAccount rejects a name already taken, so that pair is
+  // a card the tree exposed twice, or two names the merged key cannot tell
+  // apart.
+  const mergedKey = initialsOf(typed) + typed;
+  const matches = after.filter(account => account.name === typed || account.name === mergedKey);
   const created = matches.length === 1 ? matches[0] : undefined;
   if (created === undefined) return false;
   if (before.some(account => account.name === created.name)) return false;

pkg/spec/test/folio-new-account.test.ts

@@ -1,7 +1,10 @@
 import assert from "node:assert/strict";
 import { test } from "node:test";
 
-import { createdAccountHasNonZeroBalance } from "../../../examples/folio/sanderling/predicates.ts";
+import {
+  createdAccountHasNonZeroBalance,
+  initialsOf,
+} from "../../../examples/folio/sanderling/predicates.ts";
 
 const created = {
   kind: "Tap",
@@ -209,9 +212,90 @@ test("the merged web key still matches the name that was typed", () => {
   );
 });
 
-// Two cards answering to one typed name leave the appearance unattributable:
+// The avatar the merged web key opens with, hand-computed off Format.kt rather
-// the fuzzer creates duplicates from a five-name list, and the tree has been
+// than off the mirror, because a mirror checked against itself checks nothing.
-// seen exposing the same card twice on a transition frame.
+// A single word gives its first two characters, several give the first letter
+// of the first and of the last, and an empty name gives "?".
+test("the initials a merged key opens with are the app's", () => {
+  const named: [string, string][] = [
+    ["CH", "Checking"],
+    ["SA", "Savings"],
+    ["TR", "Travel"],
+    ["EF", "Emergency Fund"],
+    ["IN", "Investments"],
+    ["FU", "Fund"],
+    ["T2", "Travel 2024"],
+    ["A", "a"],
+    ["X9", "x9"],
+    ["-1", "-1"],
+    ["?", ""],
+    ["?", "   "],
+  ];
+  for (const [initials, name] of named) {
+    assert.equal(initialsOf(name), initials, `initials for ${JSON.stringify(name)}`);
+  }
+});
+
+// The attribution used to be a suffix test, and a suffix test hands the verdict
+// to whichever OTHER account happens to end with the typed name. Home lists
+// what fits the viewport, so the card that was just created is clipped out of
+// the reading exactly as easily as any other, and the older account left in it
+// is then judged for money it has held all along.
+test("an older account whose name ends with the typed one is not the created one", () => {
+  assert.equal(
+    createdAccountHasNonZeroBalance({
+      route: "home",
+      lastAction: created,
+      typedName: "Fund",
+      before: [account("Checking", 0)],
+      after: [account("Checking", 0), account("Emergency Fund", 461012300)],
+    }),
+    false,
+  );
+});
+
+test("the merged web key is matched whole too, not by its ending", () => {
+  assert.equal(
+    createdAccountHasNonZeroBalance({
+      route: "home",
+      lastAction: created,
+      typedName: "Fund",
+      before: [account("CHChecking", 0)],
+      after: [account("CHChecking", 0), account("EFEmergency Fund", 461012300)],
+    }),
+    false,
+  );
+});
+
+// The card that was actually asked for is still judged, standing next to the
+// account that merely ends with its name.
+test("the created card is judged beside an account whose name ends with it", () => {
+  assert.equal(
+    createdAccountHasNonZeroBalance({
+      route: "home",
+      lastAction: created,
+      typedName: "Fund",
+      before: [account("Emergency Fund", 461012300)],
+      after: [account("Emergency Fund", 461012300), account("Fund", 5000)],
+    }),
+    true,
+  );
+  assert.equal(
+    createdAccountHasNonZeroBalance({
+      route: "home",
+      lastAction: created,
+      typedName: "Fund",
+      before: [account("EFEmergency Fund", 461012300)],
+      after: [account("EFEmergency Fund", 461012300), account("FUFund", 5000)],
+    }),
+    true,
+  );
+});
+
+// Two cards answering to one typed name leave the appearance unattributable.
+// Accounts.name is UNIQUE and Repository.createAccount rejects a name already
+// taken, so the pair is one card the tree exposed twice on a transition frame,
+// or two names the merged web key cannot tell apart.
 test("two cards matching the typed name are not attributable to the creation", () => {
   assert.equal(
     createdAccountHasNonZeroBalance({
@@ -219,7 +303,7 @@ test("two cards matching the typed name are not attributable to the creation", (
       lastAction: created,
       typedName: "Travel",
       before: [account("Checking", 0)],
-      after: [account("Checking", 0), account("Travel", 5000), account("MyTravel", 900)],
+      after: [account("Checking", 0), account("Travel", 5000), account("Travel", 900)],
     }),
     false,
   );