katex: Remove renderKaTex experimental flag

This flag has been enabled since v0.0.29 (beta) release, and we
don't plan to disable it. So remove the flag completely,
simplifying related code.

Fixes: #1728

Author: rajveermalviya

lib/model/katex.dart

@@ -116,31 +116,27 @@ MathParserResult? parseMath(dom.Element element, { required bool block }) {
     // content parsing stage here, thus the `!` here.
     final globalStore = ZulipBinding.instance.getGlobalStoreSync()!;
     final globalSettings = globalStore.settings;
-    final flagRenderKatex =
-      globalSettings.getBool(BoolGlobalSetting.renderKatex);
     final flagForceRenderKatex =
       globalSettings.getBool(BoolGlobalSetting.forceRenderKatex);
 
     KatexParserHardFailReason? hardFailReason;
     KatexParserSoftFailReason? softFailReason;
     List<KatexNode>? nodes;
-    if (flagRenderKatex) {
-      final parser = _KatexParser();
-      try {
-        nodes = parser.parseKatexHtml(katexHtmlElement);
-      } on _KatexHtmlParseError catch (e, st) {
-        assert(debugLog('$e\n$st'));
-        hardFailReason = KatexParserHardFailReason(
-          message: e.message,
-          stackTrace: st);
-      }
+    final parser = _KatexParser();
+    try {
+      nodes = parser.parseKatexHtml(katexHtmlElement);
+    } on _KatexHtmlParseError catch (e, st) {
+      assert(debugLog('$e\n$st'));
+      hardFailReason = KatexParserHardFailReason(
+        message: e.message,
+        stackTrace: st);
+    }
 
-      if (parser.hasError && !flagForceRenderKatex) {
-        nodes = null;
-        softFailReason = KatexParserSoftFailReason(
-          unsupportedCssClasses: parser.unsupportedCssClasses,
-          unsupportedInlineCssProperties: parser.unsupportedInlineCssProperties);
-      }
+    if (parser.hasError && !flagForceRenderKatex) {
+      nodes = null;
+      softFailReason = KatexParserSoftFailReason(
+        unsupportedCssClasses: parser.unsupportedCssClasses,
+        unsupportedInlineCssProperties: parser.unsupportedInlineCssProperties);
     }
 
     return MathParserResult(

lib/model/settings.dart

@@ -177,16 +177,14 @@ enum BoolGlobalSetting {
   /// welcome dialog for upgrading from the legacy app.
   upgradeWelcomeDialogShown(GlobalSettingType.internal, false),
 
-  /// An experimental flag to toggle rendering KaTeX content in messages.
-  renderKatex(GlobalSettingType.experimentalFeatureFlag, true),
-
   /// An experimental flag to enable rendering KaTeX even when some
   /// errors are encountered.
   forceRenderKatex(GlobalSettingType.experimentalFeatureFlag, false),
 
   // Former settings which might exist in the database,
   // whose names should therefore not be reused:
   //   openFirstUnread  // v0.0.30
+  //   renderKatex      // v0.0.29 - v30.0.261
   ;
 
   const BoolGlobalSetting(this.type, this.default_);

test/model/content_test.dart

@@ -6,7 +6,6 @@ import 'package:stack_trace/stack_trace.dart';
 import 'package:test/scaffolding.dart';
 import 'package:zulip/model/code_block.dart';
 import 'package:zulip/model/content.dart';
-import 'package:zulip/model/settings.dart';
 import 'package:zulip/model/katex.dart';
 
 import 'binding.dart';
@@ -511,7 +510,7 @@ class ContentExample {
 
   static final mathInline = ContentExample.inline(
     'inline math',
-    r"$$ \lambda $$",
+    null, // r"$$ \lambda $$" (hypothetical server variation)
     expectedText: r'λ',
     '<p><span class="katex">'
       '<span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>λ</mi></mrow>'
@@ -528,6 +527,20 @@ class ContentExample {
       ]),
     ]));
 
+  // A test message to test the fallback behaviour of KaTeX implementation.
+  static final mathInlineUnknown = ContentExample.inline(
+    'inline math',
+    r"$$ \lambda $$",
+    expectedText: r'\lambda',
+    '<p><span class="katex">'
+      '<span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>λ</mi></mrow>'
+        '<annotation encoding="application/x-tex"> \\lambda </annotation></semantics></math></span>'
+      '<span class="katex-html" aria-hidden="true">'
+        '<span class="base unknown">' // Server doesn't generate this 'unknown' class.
+        '<span class="strut" style="height:0.6944em;"></span>'
+        '<span class="mord mathnormal">λ</span></span></span></span></p>',
+    MathInlineNode(texSource: r'\lambda', nodes: null));
+
   static const mathBlock = ContentExample(
     'math block',
     "```math\n\\lambda\n```",
@@ -547,6 +560,20 @@ class ContentExample {
       ]),
     ])]);
 
+  // A test message to test the fallback behaviour of KaTeX implementation.
+  static const mathBlockUnknown = ContentExample(
+    'math block unknown, fallback to TeX source',
+    null, // r"```math\n\lambda\n```" (hypothetical server variation)
+    expectedText: r'\lambda',
+    '<p><span class="katex-display"><span class="katex">'
+      '<span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>λ</mi></mrow>'
+        '<annotation encoding="application/x-tex">\\lambda</annotation></semantics></math></span>'
+      '<span class="katex-html" aria-hidden="true">'
+        '<span class="base unknown">' // Server doesn't generate this 'unknown' class.
+          '<span class="strut" style="height:0.6944em;"></span>'
+          '<span class="mord mathnormal">λ</span></span></span></span></span></p>',
+    [MathBlockNode(texSource: r'\lambda', nodes: null)]);
+
   static const mathBlocksMultipleInParagraph = ContentExample(
     'math blocks, multiple in paragraph',
     '```math\na\n\nb\n```',
@@ -1484,10 +1511,6 @@ void main() async {
 
   TestZulipBinding.ensureInitialized();
 
-  // We need this to be able to test the currently experimental KaTeX code.
-  await testBinding.globalStore.settings.setBool(
-    BoolGlobalSetting.renderKatex, true);
-
   //
   // Inline content.
   //
@@ -1599,6 +1622,7 @@ void main() async {
   testParseExample(ContentExample.emojiZulipExtra);
 
   testParseExample(ContentExample.mathInline);
+  testParseExample(ContentExample.mathInlineUnknown);
 
   group('global times', () {
     testParseExample(ContentExample.globalTime);
@@ -1777,6 +1801,8 @@ void main() async {
   // into the context of a Zulip message.
   // For tests going deeper inside KaTeX content, see katex_test.dart.
   testParseExample(ContentExample.mathBlock);
+  testParseExample(ContentExample.mathBlockUnknown);
+
   testParseExample(ContentExample.mathBlocksMultipleInParagraph);
   testParseExample(ContentExample.mathBlockInQuote);
   testParseExample(ContentExample.mathBlocksMultipleInQuote);

test/model/katex_test.dart

@@ -1,6 +1,5 @@
 import 'dart:io';
 
-import 'package:zulip/model/settings.dart';
 import 'package:checks/checks.dart';
 import 'package:stack_trace/stack_trace.dart';
 import 'package:test_api/scaffolding.dart';
@@ -572,9 +571,6 @@ class KatexExample extends ContentExample {
 void main() async {
   TestZulipBinding.ensureInitialized();
 
-  await testBinding.globalStore.settings.setBool(
-    BoolGlobalSetting.renderKatex, true);
-
   testParseExample(KatexExample.mathBlockKatexSizing);
   testParseExample(KatexExample.mathBlockKatexNestedSizing);
   testParseExample(KatexExample.mathBlockKatexDelimSizing);

test/widgets/content_test.dart

@@ -23,7 +23,6 @@ import '../example_data.dart' as eg;
 import '../flutter_checks.dart';
 import '../model/binding.dart';
 import '../model/content_test.dart';
-import '../model/store_checks.dart';
 import '../model/test_store.dart';
 import '../test_images.dart';
 import '../test_navigation.dart';
@@ -560,22 +559,13 @@ void main() {
 
     testContentSmoke(ContentExample.mathBlock);
 
-    testWidgets('displays KaTeX content; experimental flag enabled', (tester) async {
-      addTearDown(testBinding.reset);
-      final globalSettings = testBinding.globalStore.settings;
-      await globalSettings.setBool(BoolGlobalSetting.renderKatex, true);
-      check(globalSettings).getBool(BoolGlobalSetting.renderKatex).isTrue();
-
+    testWidgets('displays KaTeX content', (tester) async {
       await prepareContent(tester, plainContent(ContentExample.mathBlock.html));
       tester.widget(find.text('λ', findRichText: true));
     });
 
-    testWidgets('displays KaTeX source; experimental flag disabled', (tester) async {
-      addTearDown(testBinding.reset);
-      final globalSettings = testBinding.globalStore.settings;
-      await globalSettings.setBool(BoolGlobalSetting.renderKatex, false);
-
-      await prepareContent(tester, plainContent(ContentExample.mathBlock.html));
+    testWidgets('fallback to displaying KaTeX source if unsupported KaTeX HTML', (tester) async {
+      await prepareContent(tester, plainContent(ContentExample.mathBlockUnknown.html));
       tester.widget(find.text(r'\lambda', findRichText: true));
     });
   });
@@ -992,11 +982,6 @@ void main() {
     testContentSmoke(ContentExample.mathInline);
 
     testWidgets('maintains font-size ratio with surrounding text', (tester) async {
-      addTearDown(testBinding.reset);
-      final globalSettings = testBinding.globalStore.settings;
-      await globalSettings.setBool(BoolGlobalSetting.renderKatex, true);
-      check(globalSettings.getBool(BoolGlobalSetting.renderKatex)).isTrue();
-
       const html = '<span class="katex">'
         '<span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>λ</mi></mrow>'
           '<annotation encoding="application/x-tex"> \\lambda </annotation></semantics></math></span>'
@@ -1017,37 +1002,27 @@ void main() {
         });
     });
 
-    testWidgets('maintains font-size ratio with surrounding text, when showing TeX source', (tester) async {
-      addTearDown(testBinding.reset);
-      final globalSettings = testBinding.globalStore.settings;
-      await globalSettings.setBool(BoolGlobalSetting.renderKatex, false);
-
-      const html = '<span class="katex">'
+    testWidgets('maintains font-size ratio with surrounding text, when falling back to TeX source', (tester) async {
+      const unsupportedHtml = '<span class="katex">'
         '<span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>λ</mi></mrow>'
           '<annotation encoding="application/x-tex"> \\lambda </annotation></semantics></math></span>'
-        '<span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">λ</span></span></span></span>';
+        '<span class="katex-html" aria-hidden="true">'
+          '<span class="base unknown">' // Server doesn't generate this 'unknown' class.
+          '<span class="strut" style="height:0.6944em;"></span>'
+          '<span class="mord mathnormal">λ</span></span></span></span>';
       await checkFontSizeRatio(tester,
-        targetHtml: html,
+        targetHtml: unsupportedHtml,
         targetFontSizeFinder: mkTargetFontSizeFinderFromPattern(r'\lambda'));
     });
 
-    testWidgets('displays KaTeX content; experimental flag enabled', (tester) async {
-      addTearDown(testBinding.reset);
-      final globalSettings = testBinding.globalStore.settings;
-      await globalSettings.setBool(BoolGlobalSetting.renderKatex, true);
-      check(globalSettings.getBool(BoolGlobalSetting.renderKatex)).isTrue();
-
+    testWidgets('displays KaTeX content', (tester) async {
       await prepareContent(tester, plainContent(ContentExample.mathInline.html));
       tester.widget(find.text('λ', findRichText: true));
     });
 
-    testWidgets('displays KaTeX source; experimental flag disabled', (tester) async {
-      addTearDown(testBinding.reset);
-      final globalSettings = testBinding.globalStore.settings;
-      await globalSettings.setBool(BoolGlobalSetting.renderKatex, false);
-
-      await prepareContent(tester, plainContent(ContentExample.mathInline.html));
-      tester.widget(find.text(r'\lambda', findRichText: true));
+    testWidgets('fallback to displaying KaTeX source if unsupported KaTeX HTML', (tester) async {
+      await prepareContent(tester, plainContent(ContentExample.mathInlineUnknown.html));
+      tester.widget(find.text(r'\lambda'));
     });
   });
 

test/widgets/katex_test.dart

@@ -2,12 +2,10 @@ import 'package:checks/checks.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_checks/flutter_checks.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:zulip/model/settings.dart';
 import 'package:zulip/widgets/katex.dart';
 
 import '../model/binding.dart';
 import '../model/katex_test.dart';
-import '../model/store_checks.dart';
 import 'content_test.dart';
 
 void main() {
@@ -81,11 +79,6 @@ void main() {
         testWidgets(testCase.$1.description, (tester) async {
           await _loadKatexFonts();
 
-          addTearDown(testBinding.reset);
-          final globalSettings = testBinding.globalStore.settings;
-          await globalSettings.setBool(BoolGlobalSetting.renderKatex, true);
-          check(globalSettings).getBool(BoolGlobalSetting.renderKatex).isTrue();
-
           await prepareContent(tester, plainContent(testCase.$1.html));
 
           final baseRect = tester.getRect(find.byType(KatexWidget));

tools/content/unimplemented_katex_test.dart

@@ -10,15 +10,12 @@ import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:zulip/model/content.dart';
-import 'package:zulip/model/settings.dart';
 
 import '../../test/model/binding.dart';
 import 'model.dart';
 
 void main() async {
   TestZulipBinding.ensureInitialized();
-  await testBinding.globalStore.settings.setBool(
-    BoolGlobalSetting.renderKatex, true);
 
   Future<void> checkForKatexFailuresInFile(File file) async {
     int totalMessageCount = 0;