Better checking of improperly nested AMS environments. (mathjax/MathJ…

…ax#1892)
mathjax · Feb 25, 2023 · 7bb5fbd · 7bb5fbd
1 parent 4464efc
commit 7bb5fbd
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Showing 4 changed files with 22 additions and 11 deletions.
diff --git a/ts/input/tex/ParseUtil.ts b/ts/input/tex/ParseUtil.ts
@@ -535,12 +535,18 @@ namespace ParseUtil {
   /**
    *  Check for bad nesting of equation environments
    */
-  export function checkEqnEnv(parser: TexParser) {
-    if (parser.stack.global.eqnenv) {
-      // @test ErroneousNestingEq
+  export function checkEqnEnv(parser: TexParser, nestable: boolean = true) {
+    const top = parser.stack.Top();
+    const first = top.First;
+    //
+    // The gather environment can include align and others, but only one level deep.
+    //
+    if (top.getProperty('nestable') && nestable && !first) {
+      return;
+    }
+    if (!top.isKind('start') || first) {
       throw new TexError('ErroneousNestingEq', 'Erroneous nesting of equation structures');
     }
-    parser.stack.global.eqnenv = true;
   }
 
   /**

diff --git a/ts/input/tex/ams/AmsMethods.ts b/ts/input/tex/ams/AmsMethods.ts
@@ -115,8 +115,8 @@ AmsMethods.AlignAt = function(parser: TexParser, begin: StackItem,
  */
 AmsMethods.Multline = function (parser: TexParser, begin: StackItem, numbered: boolean) {
   // @test Shove*, Multline
-  parser.Push(begin);
   ParseUtil.checkEqnEnv(parser);
+  parser.Push(begin);
   const item = parser.itemFactory.create('multline', numbered, parser.stack) as ArrayItem;
   item.arraydef = {
     displaystyle: true,
@@ -170,8 +170,8 @@ AmsMethods.XalignAt = function(parser: TexParser, begin: StackItem,
 AmsMethods.FlalignArray = function(parser: TexParser, begin: StackItem, numbered: boolean,
                                   padded: boolean, center: boolean, align: string,
                                   width: string, zeroWidthLabel: boolean = false) {
-  parser.Push(begin);
   ParseUtil.checkEqnEnv(parser);
+  parser.Push(begin);
   align = align
     .split('')
     .join(' ')

diff --git a/ts/input/tex/base/BaseMethods.ts b/ts/input/tex/base/BaseMethods.ts
@@ -1468,8 +1468,8 @@ BaseMethods.AlignedArray = function(parser: TexParser, begin: StackItem) {
  * @param {boolean} numbered True if environment is numbered.
  */
 BaseMethods.Equation = function (parser: TexParser, begin: StackItem, numbered: boolean) {
-  parser.Push(begin);
   ParseUtil.checkEqnEnv(parser);
+  parser.Push(begin);
   return parser.itemFactory.create('equation', numbered).
     setProperty('name', begin.getName());
 };
@@ -1488,13 +1488,15 @@ BaseMethods.EqnArray = function(parser: TexParser, begin: StackItem,
                                 numbered: boolean, taggable: boolean,
                                 align: string, spacing: string) {
   // @test The Lorenz Equations, Maxwell's Equations, Cubic Binomial
-  parser.Push(begin);
+  let name = begin.getName();
+  let isGather = (name === 'gather' || name === 'gather*');
   if (taggable) {
-    ParseUtil.checkEqnEnv(parser);
+    ParseUtil.checkEqnEnv(parser, !isGather);
   }
+  parser.Push(begin);
   align = align.replace(/[^clr]/g, '').split('').join(' ');
   align = align.replace(/l/g, 'left').replace(/r/g, 'right').replace(/c/g, 'center');
-  let newItem = parser.itemFactory.create('eqnarray', begin.getName(),
+  let newItem = parser.itemFactory.create('eqnarray', name,
                                           numbered, taggable, parser.stack.global) as sitem.ArrayItem;
   newItem.arraydef = {
     displaystyle: true,
@@ -1504,6 +1506,9 @@ BaseMethods.EqnArray = function(parser: TexParser, begin: StackItem,
     side: parser.options['tagSide'],
     minlabelspacing: parser.options['tagIndent']
   };
+  if (isGather) {
+    newItem.setProperty('nestable', true);
+  }
   return newItem;
 };
 

diff --git a/ts/input/tex/empheq/EmpheqConfiguration.ts b/ts/input/tex/empheq/EmpheqConfiguration.ts
@@ -77,12 +77,12 @@ export const EmpheqMethods = {
       parser.Push(parser.itemFactory.create('end').setProperty('name', 'empheq'));
     } else {
       ParseUtil.checkEqnEnv(parser);
-      delete parser.stack.global.eqnenv;
       const opts = parser.GetBrackets('\\begin{' + begin.getName() + '}') || '';
       const [env, n] = (parser.GetArgument('\\begin{' + begin.getName() + '}') || '').split(/=/);
       if (!EmpheqUtil.checkEnv(env)) {
         throw new TexError('UnknownEnv', 'Unknown environment "%1"', env);
       }
+      begin.setProperty('nestable', true);
       if (opts) {
         begin.setProperties(EmpheqUtil.splitOptions(opts, {left: 1, right: 1}));
       }