Fix typo in \DeclarePairedDelimiter and related macros, and allow arg…

…ument substitution in pre and post sections as well as body. (mathjax/MathJax#2816, mathjax/MathJax#2758)

ts/input/tex/mathtools/MathtoolsMappings.ts

@@ -94,9 +94,16 @@ new CommandMap('mathtools-macros', {
   MTFlushSpaceAbove: 'FlushSpaceAbove',
   MTFlushSpaceBelow: 'FlushSpaceBelow',
 
-  DeclarePairedDelimiters:    'DeclarePairedDelimiters',
-  DeclarePairedDelimitersX:   'DeclarePairedDelimitersX',
-  DeclarePairedDelimitersXPP: 'DeclarePairedDelimitersXPP',
+  DeclarePairedDelimiter:     'DeclarePairedDelimiter',
+  DeclarePairedDelimiterX:    'DeclarePairedDelimiterX',
+  DeclarePairedDelimiterXPP:  'DeclarePairedDelimiterXPP',
+
+  //
+  //  Typos from initial release -- kept for backward compatibility for now
+  //
+  DeclarePairedDelimiters:    'DeclarePairedDelimiter',
+  DeclarePairedDelimitersX:   'DeclarePairedDelimiterX',
+  DeclarePairedDelimitersXPP: 'DeclarePairedDelimiterXPP',
 
   centercolon: ['CenterColon', true, true],
   ordinarycolon: ['CenterColon', false],

ts/input/tex/mathtools/MathtoolsMethods.ts

@@ -480,7 +480,9 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
       for (let i = args.length; i < n; i++) {
         args.push(parser.GetArgument(name));
       }
+      pre  = ParseUtil.substituteArgs(parser, args, pre);
       body = ParseUtil.substituteArgs(parser, args, body);
+      post = ParseUtil.substituteArgs(parser, args, post);
     }
     body = body.replace(/\\delimsize/g, delim);
     parser.string = [pre, left, open, body, right, close, post, parser.string.substr(parser.i)]
@@ -490,25 +492,25 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
   },
 
   /**
-   * Implements \DeclarePairedDelimiters.
+   * Implements \DeclarePairedDelimiter.
    *
    * @param {TexParser} parser   The calling parser.
    * @param {string} name        The macro name.
    */
-  DeclarePairedDelimiters(parser: TexParser, name: string) {
+  DeclarePairedDelimiter(parser: TexParser, name: string) {
     const cs = NewcommandUtil.GetCsNameArgument(parser, name);
     const open = parser.GetArgument(name);
     const close = parser.GetArgument(name);
     MathtoolsUtil.addPairedDelims(parser.configuration, cs, [open, close]);
   },
 
   /**
-   * Implements \DeclarePairedDelimitersX.
+   * Implements \DeclarePairedDelimiterX.
    *
    * @param {TexParser} parser   The calling parser.
    * @param {string} name        The macro name.
    */
-  DeclarePairedDelimitersX(parser: TexParser, name: string) {
+  DeclarePairedDelimiterX(parser: TexParser, name: string) {
     const cs = NewcommandUtil.GetCsNameArgument(parser, name);
     const n = NewcommandUtil.GetArgCount(parser, name);
     const open = parser.GetArgument(name);
@@ -518,12 +520,12 @@ export const MathtoolsMethods: Record<string, ParseMethod> = {
   },
 
   /**
-   * Implements \DeclarePairedDelimitersXPP.
+   * Implements \DeclarePairedDelimiterXPP.
    *
    * @param {TexParser} parser   The calling parser.
    * @param {string} name        The macro name.
    */
-  DeclarePairedDelimitersXPP(parser: TexParser, name: string) {
+  DeclarePairedDelimiterXPP(parser: TexParser, name: string) {
     const cs = NewcommandUtil.GetCsNameArgument(parser, name);
     const n = NewcommandUtil.GetArgCount(parser, name);
     const pre = parser.GetArgument(name);