Add unicode bidi isolates to i18n substitutions for strings

ts/test-both/util/unicodeBidi_test.ts

@@ -0,0 +1,98 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import {
+  FIRST_STRONG_ISOLATE as FSI,
+  POP_DIRECTIONAL_ISOLATE as PSI,
+  LTR_ISOLATE,
+  POP_DIRECTIONAL_FORMATTING,
+  RTL_ISOLATE,
+  _bidiIsolate,
+  LTR_EMBEDDING,
+  LTR_OVERRIDE,
+  RTL_EMBEDDING,
+  RTL_OVERRIDE,
+} from '../../util/unicodeBidi';
+
+function debugUnicode(text: string) {
+  return text
+    .split('')
+    .map(char => char.charCodeAt(0).toString(16))
+    .join(' ');
+}
+
+function assertEqual(actual: string, expected: string) {
+  assert.equal(debugUnicode(actual), debugUnicode(expected));
+}
+
+describe('_bidiIsolate', () => {
+  it('returns a string with bidi isolate characters', () => {
+    const actual = _bidiIsolate('Hello');
+    assertEqual(actual, `${FSI}Hello${PSI}`);
+  });
+
+  it('strips unopened pop isolate characters', () => {
+    const actual = _bidiIsolate(`${PSI}Hello`);
+    assertEqual(actual, `${FSI}Hello${PSI}`);
+  });
+
+  it('strips unopened pop formatting characters', () => {
+    const actual = _bidiIsolate(`${POP_DIRECTIONAL_FORMATTING}Hello`);
+    assertEqual(actual, `${FSI}Hello${PSI}`);
+  });
+
+  it('closes isolates that were left open', () => {
+    const actual = _bidiIsolate(`${LTR_ISOLATE}${RTL_ISOLATE}${FSI}Hello`);
+    assertEqual(
+      actual,
+      `${FSI}${LTR_ISOLATE}${RTL_ISOLATE}${FSI}Hello${PSI}${PSI}${PSI}${PSI}`
+    );
+  });
+
+  it('closes overrides that were left open', () => {
+    const actual = _bidiIsolate(`${LTR_OVERRIDE}${RTL_OVERRIDE}Hello`);
+    assertEqual(
+      actual,
+      `${FSI}${LTR_OVERRIDE}${RTL_OVERRIDE}Hello${POP_DIRECTIONAL_FORMATTING}${POP_DIRECTIONAL_FORMATTING}${PSI}`
+    );
+  });
+
+  it('closes formatting that was left open', () => {
+    const actual = _bidiIsolate(`${LTR_EMBEDDING}${RTL_EMBEDDING}Hello`);
+    assertEqual(
+      actual,
+      `${FSI}${LTR_EMBEDDING}${RTL_EMBEDDING}Hello${POP_DIRECTIONAL_FORMATTING}${POP_DIRECTIONAL_FORMATTING}${PSI}`
+    );
+  });
+
+  it('leaves properly balanced isolates alone', () => {
+    const actual = _bidiIsolate(
+      `${FSI}${LTR_ISOLATE}${RTL_ISOLATE}${PSI}${PSI}${PSI}Hello`
+    );
+    assertEqual(
+      actual,
+      `${FSI}${FSI}${LTR_ISOLATE}${RTL_ISOLATE}${PSI}${PSI}${PSI}Hello${PSI}`
+    );
+  });
+
+  it('leaves properly balanced overrides alone', () => {
+    const actual = _bidiIsolate(
+      `${LTR_OVERRIDE}${RTL_OVERRIDE}${POP_DIRECTIONAL_FORMATTING}${POP_DIRECTIONAL_FORMATTING}Hello`
+    );
+    assertEqual(
+      actual,
+      `${FSI}${LTR_OVERRIDE}${RTL_OVERRIDE}${POP_DIRECTIONAL_FORMATTING}${POP_DIRECTIONAL_FORMATTING}Hello${PSI}`
+    );
+  });
+
+  it('leaves properly balanced formatting alone', () => {
+    const actual = _bidiIsolate(
+      `${LTR_EMBEDDING}${RTL_EMBEDDING}${POP_DIRECTIONAL_FORMATTING}${POP_DIRECTIONAL_FORMATTING}Hello`
+    );
+    assertEqual(
+      actual,
+      `${FSI}${LTR_EMBEDDING}${RTL_EMBEDDING}${POP_DIRECTIONAL_FORMATTING}${POP_DIRECTIONAL_FORMATTING}Hello${PSI}`
+    );
+  });
+});