Updated to only add numbering to slugified heading anchors when absolutely neccessary

app/components/Editor/components/Contents.js

@@ -64,14 +64,16 @@ class Contents extends Component {
   }
 
   render() {
+    const { editor } = this.props;
+
     // If there are one or less headings in the document no need for a minimap
     if (this.headings.size <= 1) return null;
 
     return (
       <Wrapper>
         <Sections>
-          {this.headings.map((heading, index) => {
+          {this.headings.map(heading => {
-            const slug = headingToSlug(heading, index);
+            const slug = headingToSlug(editor.value.document, heading);
             const active = this.activeHeading === slug;
 
             return (

app/components/Editor/components/Heading.js

@@ -1,8 +1,7 @@
 // @flow
 import React from 'react';
-import { Document, Block } from 'slate';
+import { Document } from 'slate';
 import type { SlateNodeProps } from '../types';
-import { List } from 'immutable';
 import styled from 'styled-components';
 import headingToSlug from '../headingToSlug';
 import Placeholder from './Placeholder';
@@ -13,15 +12,6 @@ type Props = SlateNodeProps & {
   placeholder: string,
 };
 
-function indexInDocument(document, heading) {
-  const headings = document.nodes.filter((node: Block) => {
-    if (!node.text) return false;
-    return node.type.match(/^heading/);
-  });
-
-  return headings.indexOf(heading);
-}
-
 function Heading(props: Props) {
   const {
     parent,
@@ -37,10 +27,7 @@ function Heading(props: Props) {
   const parentIsDocument = parent instanceof Document;
   const firstHeading = parentIsDocument && parent.nodes.first() === node;
   const showPlaceholder = placeholder && firstHeading && !node.text;
-  const slugish = headingToSlug(
+  const slugish = headingToSlug(editor.value.document, node);
-    node,
-    indexInDocument(editor.value.document, node)
-  );
   const showHash = readOnly && !!slugish;
   const Component = component;
   const emoji = editor.props.emoji || '';

app/components/Editor/headingToSlug.js

@@ -1,10 +1,25 @@
 // @flow
 import { escape } from 'lodash';
-import { Node } from 'slate';
+import { Document, Block, Node } from 'slate';
 import slug from 'slug';
 
-export default function headingToSlug(node: Node, index: number = 0) {
+// finds the index of this heading in the document compared to other headings
-  const slugified = escape(slug(node.text));
+// with the same slugified text
-  if (index === 0) return slugified;
+function indexOfType(document, heading) {
-  return `${index}-${slugified}`;
+  const slugified = escape(slug(heading.text));
+  const headings = document.nodes.filter((node: Block) => {
+    if (!node.text) return false;
+    return node.type.match(/^heading/) && slugified === escape(slug(node.text));
+  });
+
+  return headings.indexOf(heading);
+}
+
+// calculates a unique slug for this heading based on it's text and position
+// in the document that is as stable as possible
+export default function headingToSlug(document: Document, node: Node) {
+  const slugified = escape(slug(node.text));
+  const index = indexOfType(document, node);
+  if (index === 0) return slugified;
+  return `${slugified}-${index}`;
 }