sourcemap-tools: add doc about regexp in DebugIdGenerator

Author: perf2711

tools/sourcemap-tools/src/DebugIdGenerator.ts

@@ -2,6 +2,11 @@ export const SOURCE_DEBUG_ID_VARIABLE = '_btDebugIds';
 export const SOURCE_DEBUG_ID_COMMENT = 'debugId';
 export const SOURCEMAP_DEBUG_ID_KEY = 'debugId';
 
+/**
+ * Matches leading and trailing semicolons, e.g. in `;;foo;bar;;`
+ */
+const MATCH_SEMICOLONS_REGEX = /^;+|;+$/;
+
 export class DebugIdGenerator {
     public generateSourceSnippet(uuid: string) {
         return `;!function(){try{var k="${SOURCE_DEBUG_ID_VARIABLE}",u="undefined",v="${uuid}",a=function(x){try{x[k]=x[k]||{};x[k][n]=v}catch{}},n=(new Error).stack;n&&(u!=typeof window?a(window):u);n&&(u!=typeof global?a(global):u);n&&(u!=typeof self?a(self):u);n&&(u!=typeof globalThis?a(globalThis):u)}catch{}}();`;
@@ -15,7 +20,7 @@ export class DebugIdGenerator {
         const replaceAll = () => source.replace(oldDebugId, newDebugId);
 
         // Try to replace more safely first
-        const oldSourceSnippet = this.generateSourceSnippet(oldDebugId).replace(/^;+|;+$/g, '');
+        const oldSourceSnippet = this.generateSourceSnippet(oldDebugId).replace(MATCH_SEMICOLONS_REGEX, '');
         if (source.indexOf(oldSourceSnippet) !== -1) {
             source = source.replace(oldSourceSnippet, this.generateSourceSnippet(newDebugId));
         } else {
@@ -33,7 +38,7 @@ export class DebugIdGenerator {
     }
 
     public hasCodeSnippet(source: string, debugId: string) {
-        const sourceSnippet = this.generateSourceSnippet(debugId).replace(/^;+|;+$/g, '');
+        const sourceSnippet = this.generateSourceSnippet(debugId).replace(MATCH_SEMICOLONS_REGEX, '');
         return source.includes(sourceSnippet);
     }