Fix handling of _ and ^ followed by command that doesn't push content (mathjax/MathJax#3184)

ts/input/tex/Stack.ts

@@ -99,7 +99,9 @@ export default class Stack {
         this.Push(...top);
         continue;
       }
-      this.stack.push(item);
+      if (!item.isKind('null')) {
+        this.stack.push(item);
+      }
       if (item.env) {
         if (item.copyEnv) {
           Object.assign(item.env, this.env);

ts/input/tex/StackItem.ts

@@ -414,7 +414,7 @@ export abstract class BaseItem extends MmlStack implements StackItem {
   /**
    * @return {string} The type of the stack item.
    */
-    public get kind(): string {
+  public get kind(): string {
     return 'base';
   }
 

ts/input/tex/TexParser.ts

@@ -570,11 +570,13 @@ export default class TexParser {
     }
     // These are the cases to handle sub and superscripts.
     if (node.attributes.get(TexConstant.Attr.LATEX) === '^' &&
-      str !== '^' && str !== '\\^') {
-      if (str === '}') {
-        this.composeBraces(node.childNodes[2]);
-      } else {
-        node.childNodes[2].attributes.set(TexConstant.Attr.LATEX, str);
+        str !== '^' && str !== '\\^') {
+      if (node.childNodes[2]) {
+        if (str === '}') {
+          this.composeBraces(node.childNodes[2]);
+        } else {
+          node.childNodes[2].attributes.set(TexConstant.Attr.LATEX, str);
+        }
       }
       if (node.childNodes[1]) {
         const sub = node.childNodes[1].attributes.get(TexConstant.Attr.LATEX);
@@ -585,11 +587,13 @@ export default class TexParser {
       return;
     }
     if (node.attributes.get(TexConstant.Attr.LATEX) === '_' &&
-      str !== '_' && str !== '\\_') {
-      if (str === '}') {
-        this.composeBraces(node.childNodes[1]);
-      } else {
-        node.childNodes[1].attributes.set(TexConstant.Attr.LATEX, str);
+        str !== '_' && str !== '\\_') {
+      if (node.childNodes[1]) {
+        if (str === '}') {
+          this.composeBraces(node.childNodes[1]);
+        } else {
+          node.childNodes[1].attributes.set(TexConstant.Attr.LATEX, str);
+        }
       }
       if (node.childNodes[2]) {
         const sub = node.childNodes[2].attributes.get(TexConstant.Attr.LATEX);
@@ -616,6 +620,7 @@ export default class TexParser {
    */
   private composeLatex(
     node: MmlNode, comp: string, pos1: number, pos2: number) {
+    if (!node.childNodes[pos1] || !node.childNodes[pos2]) return;
     const expr = node.childNodes[pos1].attributes.get(TexConstant.Attr.LATEX) + comp +
       node.childNodes[pos2].attributes.get(TexConstant.Attr.LATEX);
     node.attributes.set(TexConstant.Attr.LATEX, expr);

ts/input/tex/ams/AmsMethods.ts

@@ -220,6 +220,7 @@ AmsMethods.HandleDeclareOp =  function (parser: TexParser, name: string) {
   let op = parser.GetArgument(name);
   (parser.configuration.handlers.retrieve(NEW_OPS) as CommandMap).
     add(cs, new Macro(cs, AmsMethods.Macro, [`\\operatorname${star}{${op}}`]));
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 
@@ -586,6 +587,7 @@ AmsMethods.HandleTag = function(parser: TexParser, name: string) {
   let star = parser.GetStar();
   let tagId = ParseUtil.trimSpaces(parser.GetArgument(name));
   parser.tags.tag(tagId, star);
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 

ts/input/tex/base/BaseConfiguration.ts

@@ -168,6 +168,7 @@ export const BaseConfiguration: Configuration = Configuration.create(
       [bitem.StopItem.prototype.kind]: bitem.StopItem,
       [bitem.OpenItem.prototype.kind]: bitem.OpenItem,
       [bitem.CloseItem.prototype.kind]: bitem.CloseItem,
+      [bitem.NullItem.prototype.kind]: bitem.NullItem,
       [bitem.PrimeItem.prototype.kind]: bitem.PrimeItem,
       [bitem.SubsupItem.prototype.kind]: bitem.SubsupItem,
       [bitem.OverItem.prototype.kind]: bitem.OverItem,

ts/input/tex/base/BaseItems.ts

@@ -176,6 +176,18 @@ export class CloseItem extends BaseItem {
 
 }
 
+/**
+ * Item pushed when a macro doesn't produce any output.
+ */
+export class NullItem extends BaseItem {
+  /**
+   * @override
+   */
+  public get kind() {
+    return 'null';
+  }
+}
+
 
 /**
  * Item indicating an we are currently dealing with a prime mark.

ts/input/tex/base/BaseMethods.ts

@@ -268,8 +268,7 @@ BaseMethods.Prime = function(parser: TexParser, c: string) {
   } while (c === '\'' || c === entities.rsquo);
   sup = ['', '\u2032', '\u2033', '\u2034', '\u2057'][sup.length] || sup;
   const node = parser.create('token', 'mo', {variantForm: true}, sup);
-  parser.Push(
-    parser.itemFactory.create('prime', base, node) );
+  parser.Push(parser.itemFactory.create('prime', base, node));
 };
 
 
@@ -327,6 +326,7 @@ BaseMethods.MathFont = function(parser: TexParser, name: string, variant: string
  */
 BaseMethods.SetFont = function(parser: TexParser, _name: string, font: string) {
   parser.stack.env['font'] = font;
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 /**
@@ -811,6 +811,7 @@ BaseMethods.VBox = function(parser: TexParser, name: string, align: string) {
 BaseMethods.Hsize = function (parser: TexParser, name: string) {
   parser.GetNext() === '=' && parser.i++;
   parser.stack.env.hsize = parser.GetDimen(name);
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 /**
@@ -1538,10 +1539,11 @@ BaseMethods.NewColumnType = function (parser: TexParser, name: string) {
     throw new TexError('BadColumnName', 'Column specifier must be exactly one character: %1', c);
   }
   if (!n.match(/^\d+$/)) {
-    throw new TexError('PositiveIntegerArg', 'Argument to %1 must me a positive integer', n);
+    throw new TexError('PositiveIntegerArg', 'Argument to %1 must be a positive integer', n);
   }
   const cparser = parser.configuration.columnParser;
   cparser.columnHandler[c] = (state: ColumnState) => cparser.macroColumn(state, macro, parseInt(n));
+  parser.Push(parser.itemFactory.create('null'));
 }
 
 

ts/input/tex/color/ColorMethods.ts

@@ -112,6 +112,7 @@ ColorMethods.DefineColor = function (parser: TexParser, name: string) {
 
   const colorModel: ColorModel = parser.configuration.packageData.get('color').model;
   colorModel.defineColor(model, cname, def);
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 /**

ts/input/tex/extpfeil/ExtpfeilConfiguration.ts

@@ -67,6 +67,7 @@ ExtpfeilMethods.NewExtArrow = function(parser: TexParser, name: string) {
   let spaces = space.split(',');
   NewcommandUtil.addMacro(parser, cs, ExtpfeilMethods.xArrow,
                           [parseInt(chr), parseInt(spaces[0]), parseInt(spaces[1])]);
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 

ts/input/tex/mathtools/MathtoolsMethods.ts

@@ -515,6 +515,7 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
     const open = parser.GetArgument(name);
     const close = parser.GetArgument(name);
     MathtoolsUtil.addPairedDelims(parser.configuration, cs, [open, close]);
+    parser.Push(parser.itemFactory.create('null'));
   },
 
   /**
@@ -530,6 +531,7 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
     const close = parser.GetArgument(name);
     const body = parser.GetArgument(name);
     MathtoolsUtil.addPairedDelims(parser.configuration, cs, [open, close, body, n]);
+    parser.Push(parser.itemFactory.create('null'));
   },
 
   /**
@@ -547,6 +549,7 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
     const post = parser.GetArgument(name);
     const body = parser.GetArgument(name);
     MathtoolsUtil.addPairedDelims(parser.configuration, cs, [open, close, body, n, pre, post]);
+    parser.Push(parser.itemFactory.create('null'));
   },
 
   /**
@@ -710,6 +713,7 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
       throw new TexError('DuplicateTagForm', 'Duplicate tag form: %1', id);
     }
     tags.mtFormats.set(id, [left, right, format]);
+    parser.Push(parser.itemFactory.create('null'));
   },
 
   /**
@@ -726,12 +730,14 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
     const id = parser.GetArgument(name).trim();
     if (!id) {
       tags.mtCurrent = null;
+      parser.Push(parser.itemFactory.create('null'));
       return;
     }
     if (!tags.mtFormats.has(id)) {
       throw new TexError('UndefinedTagForm', 'Undefined tag form: %1', id);
     }
     tags.mtCurrent = tags.mtFormats.get(id);
+    parser.Push(parser.itemFactory.create('null'));
   },
 
   /**
@@ -756,6 +762,7 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
     for (const id of Object.keys(keys)) {
       options[id] = keys[id];
     }
+    parser.Push(parser.itemFactory.create('null'));
   },
 
   /**

ts/input/tex/newcommand/NewcommandMethods.ts

@@ -49,6 +49,7 @@ NewcommandMethods.NewCommand = function(parser: TexParser, name: string) {
   let opt = parser.GetBrackets(name);
   let def = parser.GetArgument(name);
   NewcommandUtil.addMacro(parser, cs, NewcommandMethods.Macro, [def, n, opt]);
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 
@@ -65,6 +66,7 @@ NewcommandMethods.NewEnvironment = function(parser: TexParser, name: string) {
   let bdef = parser.GetArgument(name);
   let edef = parser.GetArgument(name);
   NewcommandUtil.addEnvironment(parser, env, NewcommandMethods.BeginEnv, [true, bdef, edef, n, opt]);
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 
@@ -83,6 +85,7 @@ NewcommandMethods.MacroDef = function(parser: TexParser, name: string) {
     NewcommandUtil.addMacro(parser, cs, NewcommandMethods.Macro, [def, params]) :
     // @test Def Let
     NewcommandUtil.addMacro(parser, cs, NewcommandMethods.MacroWithTemplate, [def].concat(params));
+  parser.Push(parser.itemFactory.create('null'));
 };
 
 
@@ -112,6 +115,7 @@ NewcommandMethods.Let = function(parser: TexParser, name: string) {
     c = parser.GetNext();
   }
   const handlers = parser.configuration.handlers;
+  parser.Push(parser.itemFactory.create('null'));
   if (c === '\\') {
     // @test Let Bar, Let Brace Equal Stretchy
     name = NewcommandUtil.GetCSname(parser, name);

ts/input/tex/require/RequireConfiguration.ts

@@ -192,6 +192,7 @@ export const RequireMethods: Record<string, ParseMethod> = {
       throw new TexError('BadPackageName', 'Argument for %1 is not a valid package name', name);
     }
     RequireLoad(parser, required);
+    parser.Push(parser.itemFactory.create('null'));
   }
 
 };

ts/input/tex/setoptions/SetOptionsConfiguration.ts

@@ -113,6 +113,7 @@ const setOptionsMap = new CommandMap('setoptions', {
           config.filterValue(parser, extension, key, options[key]);
       }
     }
+    parser.Push(parser.itemFactory.create('null'));
   }
 });