Fix duplicate heading id. marked#1401

__tests__/base/footnote

@@ -11,4 +11,4 @@ footnote one[^1] and two[^two]
 
 <p>footnote one<sup id="fnref:1"><a href="#fn:1" class="footnote-ref" role="doc-noteref">1</a></sup> and two<sup id="fnref:two"><a href="#fn:two" class="footnote-ref" role="doc-noteref">2</a></sup></p>
 <div class="footnotes" role="doc-endnotes"><hr>
-<ol><li id="fn:1" role="doc-endnote"><span class="cite-text">This is the first footnote.</span><a href="#fnref:1" class="footnote-backref" role="doc-backlink">&#8617;</a></li><li id="fn:two" role="doc-endnote"><span class="cite-text">This is the second footnote.</span><a href="#fnref:two" class="footnote-backref" role="doc-backlink">&#8617;</a></li></ol></div>
+<ol><li id="fn:1" role="doc-endnote"><span class="cite-text">This is the first footnote.</span><a href="#fnref:1" class="footnote-backref" role="doc-backlink">&#8617;</a></li><li id="fn:two" role="doc-endnote"><span class="cite-text">This is the second footnote.</span><a href="#fnref:two" class="footnote-backref" role="doc-backlink">&#8617;</a></li></ol></div>

src/block-lexer.ts

@@ -336,7 +336,7 @@ export class BlockLexer {
 
         const item: Token = {
           type: TokenType.footnote,
-          refname: this.options.slug(execArr[1]),
+          refname: this.options.slug(execArr[1], false),
           text: execArr[2]
         }
 

src/helpers.ts

@@ -21,7 +21,10 @@ export function escape(html: string, encode?: boolean): string {
       return html.replace(escapeReplaceRegex, (ch: string) => replacements[ch])
     }
   } else if (escapeTestNoEncodeRegex.test(html)) {
-    return html.replace(escapeReplaceNoEncodeRegex, (ch: string) => replacements[ch])
+    return html.replace(
+      escapeReplaceNoEncodeRegex,
+      (ch: string) => replacements[ch]
+    )
   }
 
   return html
@@ -46,21 +49,41 @@ export function unescape(html: string): string {
 }
 
 const htmlTagsRegex: RegExp = /<(?:.|\n)*?>/gm
-const specialCharsRegex: RegExp = /[!\"#$%&'\(\)\*\+,\/:;<=>\?\@\[\\\]\^`\{\|\}~]/g
+const specialCharsRegex: RegExp = /[\u2000-\u206F\u2E00-\u2E7F\\'!"#$%&()*+,./:;<=>?@[\]^`{|}~]/g
 const dotSpaceRegex: RegExp = /(\s|\.)/g
 
-export function slug(str: string): string {
-  return str
-    // Remove html tags
-    .replace(htmlTagsRegex, '')
-    // Remove special characters
-    .replace(specialCharsRegex, '')
-    // Replace dots and spaces with a separator
-    .replace(dotSpaceRegex, '-')
-    // Make the whole thing lowercase
-    .toLowerCase()
+class Slugger {
+  seen: EmptyObject = {}
+
+  slug(value: string, isUnique?: boolean): string {
+    let slug = value
+      .trim()
+      // Remove html tags
+      .replace(htmlTagsRegex, '')
+      // Remove special characters
+      .replace(specialCharsRegex, '')
+      // Replace dots and spaces with a separator
+      .replace(dotSpaceRegex, '-')
+      // Make the whole thing lowercase
+      .toLowerCase()
+
+    if (isUnique !== false) {
+      if (this.seen.hasOwnProperty(slug)) {
+        const originalSlug = slug
+        do {
+          this.seen[originalSlug]++
+          slug = originalSlug + '-' + this.seen[originalSlug]
+        } while (this.seen.hasOwnProperty(slug))
+      }
+      this.seen[slug] = 0
+    }
+
+    return slug
+  }
 }
 
+export const slugger = new Slugger()
+
 // Remove trailing 'c's. Equivalent to str.replace(/c*$/, '').
 // /c*$/ is vulnerable to REDOS.
 // invert: Remove suffix of non-c chars instead. Default falsey.
@@ -120,7 +143,11 @@ export function resolveUrl(base: string, href: string): string {
   }
 }
 
-export function cleanUrl(sanitize: boolean, base: string, href: string): string {
+export function cleanUrl(
+  sanitize: boolean,
+  base: string,
+  href: string
+): string {
   if (sanitize) {
     let prot: string
 
@@ -202,4 +229,4 @@ export function isBlockRule(regExp: RegExp): boolean {
   return regExp.source.indexOf('\\n') > -1
 }
 
-export const blockCommentRegex = /<!--(?!-?>)[\s\S]*?-->/
+export const blockCommentRegex = /<!--(?!-?>)[\s\S]*?-->/

src/interfaces.ts

@@ -3,7 +3,7 @@ import {
   escape,
   resolveUrl,
   rtrim,
-  slug,
+  slugger,
   unescape
 } from './helpers'
 import { Renderer } from './renderer'
@@ -165,7 +165,7 @@ export class Options {
   xhtml?: boolean = false
   escape?: (html: string, encode?: boolean) => string = escape
   unescape?: (html: string) => string = unescape
-  slug?: (str: string) => string = slug
+  slug?: (str: string, isUnique?: boolean) => string = (str: string, isUnique?: boolean): string => slugger.slug(str, isUnique)
   rtrim?: (str: string, c: string, invert?: boolean) => string = rtrim
   resolveUrl?: (base: string, href: string) => string = resolveUrl
   cleanUrl?: (sanitize: boolean, base: string, href: string) => string = cleanUrl
@@ -187,7 +187,7 @@ export interface LexerReturns {
 }
 
 export interface EmptyObject {
-  [key: string]: string
+  [key: string]: any
 }
 
 export type NewRenderer = (execArr?: RegExpExecArray) => string
@@ -223,4 +223,8 @@ export interface BlockRule {
 export interface TablecellFlags {
   align?: Align
   header?: boolean
-}
+}
+
+export interface Footnotes {
+  [key: string]: string
+}

src/renderer.ts

@@ -1,4 +1,4 @@
-import { Options, TablecellFlags } from './interfaces'
+import { Footnotes, Options, TablecellFlags } from './interfaces'
 
 export class Renderer {
   private _footnotes: string[] = []
@@ -46,7 +46,7 @@ ${quote}</blockquote>
 `
   }
 
-  footnote(footnotes: { [key: string]: string }): string {
+  footnote(footnotes: Footnotes): string {
     let out: string = `<div class="footnotes" role="doc-endnotes">${this.hr()}<ol>`
 
     for (const refname of this._footnotes) {