Create globalGroup option to place definitions in global scope (#2091)

If true, this allows \newcommand definitions to persist across calls to
renderToString.

Fix https://github.com/KaTeX/KaTeX/issues/2070

src/Parser.js

@@ -115,9 +115,11 @@ export default class Parser {
      * Main parsing function, which parses an entire input.
      */
     parse(): AnyParseNode[] {
-        // Create a group namespace for the math expression.
-        // (LaTeX creates a new group for every $...$, $$...$$, \[...\].)
-        this.gullet.beginGroup();
+        if (!this.settings.globalGroup) {
+            // Create a group namespace for the math expression.
+            // (LaTeX creates a new group for every $...$, $$...$$, \[...\].)
+            this.gullet.beginGroup();
+        }
 
         // Use old \color behavior (same as LaTeX's \textcolor) if requested.
         // We do this within the group for the math expression, so it doesn't
@@ -133,7 +135,9 @@ export default class Parser {
         this.expect("EOF");
 
         // End the group namespace for the expression
-        this.gullet.endGroup();
+        if (!this.settings.globalGroup) {
+            this.gullet.endGroup();
+        }
         return parse;
     }
 

src/Settings.js

@@ -50,6 +50,7 @@ export type SettingsOptions = {
     trust?: boolean | TrustFunction;
     maxSize?: number;
     maxExpand?: number;
+    globalGroup?: boolean;
 };
 
 /**
@@ -76,6 +77,7 @@ export default class Settings {
     trust: boolean | TrustFunction;
     maxSize: number;
     maxExpand: number;
+    globalGroup: boolean;
 
     constructor(options: SettingsOptions) {
         // allow null options
@@ -96,6 +98,7 @@ export default class Settings {
         this.trust = utils.deflt(options.trust, false);
         this.maxSize = Math.max(0, utils.deflt(options.maxSize, Infinity));
         this.maxExpand = Math.max(0, utils.deflt(options.maxExpand, 1000));
+        this.globalGroup = utils.deflt(options.globalGroup, false);
     }
 
     /**