From e9fde5c6b9dcb517ab06dabb6f913fd7943363f9 Mon Sep 17 00:00:00 2001
From: Youri Noel Nelson <ynnelson@users.noreply.github.com>
Date: Sun, 8 Mar 2020 05:07:53 -0400
Subject: [PATCH] feat($plugin-search): improve the native search algorithm
 (#1557)

---
 .../@vuepress/plugin-search/SearchBox.vue     | 13 +++---
 .../__tests__/matchQuery.spec.js              | 42 +++++++++++++++++++
 .../@vuepress/plugin-search/match-query.js    | 42 +++++++++++++++++++
 packages/docs/docs/guide/frontmatter.md       |  7 ++++
 .../docs/docs/theme/default-theme-config.md   | 13 +++++-
 5 files changed, 107 insertions(+), 10 deletions(-)
 create mode 100644 packages/@vuepress/plugin-search/__tests__/matchQuery.spec.js
 create mode 100644 packages/@vuepress/plugin-search/match-query.js

diff --git a/packages/@vuepress/plugin-search/SearchBox.vue b/packages/@vuepress/plugin-search/SearchBox.vue
index 3e1a2cc0d8..b47f18ec6a 100644
--- a/packages/@vuepress/plugin-search/SearchBox.vue
+++ b/packages/@vuepress/plugin-search/SearchBox.vue
@@ -45,6 +45,8 @@
 </template>
 
 <script>
+import matchQuery from './match-query'
+
 /* global SEARCH_MAX_SUGGESTIONS, SEARCH_PATHS, SEARCH_HOTKEYS */
 export default {
   name: 'SearchBox',
@@ -76,11 +78,6 @@ export default {
       const { pages } = this.$site
       const max = this.$site.themeConfig.searchMaxSuggestions || SEARCH_MAX_SUGGESTIONS
       const localePath = this.$localePath
-      const matches = item => (
-        item
-        && item.title
-        && item.title.toLowerCase().indexOf(query) > -1
-      )
       const res = []
       for (let i = 0; i < pages.length; i++) {
         if (res.length >= max) break
@@ -95,13 +92,13 @@ export default {
           continue
         }
 
-        if (matches(p)) {
+        if (matchQuery(query, p)) {
           res.push(p)
         } else if (p.headers) {
           for (let j = 0; j < p.headers.length; j++) {
             if (res.length >= max) break
             const h = p.headers[j]
-            if (matches(h)) {
+            if (h.title && matchQuery(query, p, h.title)) {
               res.push(Object.assign({}, p, {
                 path: p.path + '#' + h.slug,
                 header: h
@@ -227,7 +224,7 @@ export default {
     background #fff
     width 20rem
     position absolute
-    top 1.5rem
+    top 2 rem
     border 1px solid darken($borderColor, 10%)
     border-radius 6px
     padding 0.4rem
diff --git a/packages/@vuepress/plugin-search/__tests__/matchQuery.spec.js b/packages/@vuepress/plugin-search/__tests__/matchQuery.spec.js
new file mode 100644
index 0000000000..454e398944
--- /dev/null
+++ b/packages/@vuepress/plugin-search/__tests__/matchQuery.spec.js
@@ -0,0 +1,42 @@
+import matchQuery from '../match-query'
+
+describe('matchQuery', () => {
+  const page = {
+    title: 'HoMe PaGe',
+    frontmatter: {
+      tags: ['vuepress', 'is', 'jUst    AwEsOme']
+    }
+  }
+
+  test('should match when query includes part of the page title', () => {
+    const query = 'hom'
+
+    const match = matchQuery(query, page)
+
+    expect(match).toBe(true)
+  })
+
+  test('should match when query includes the full page title', () => {
+    const query = 'home     page'
+
+    const match = matchQuery(query, page)
+
+    expect(match).toBe(true)
+  })
+
+  test('should match when query includes a tag', () => {
+    const query = 'vuepress'
+
+    const match = matchQuery(query, page)
+
+    expect(match).toBe(true)
+  })
+
+  test('should match when query includes part of tag', () => {
+    const query = 'just aw'
+
+    const match = matchQuery(query, page)
+
+    expect(match).toBe(true)
+  })
+})
diff --git a/packages/@vuepress/plugin-search/match-query.js b/packages/@vuepress/plugin-search/match-query.js
new file mode 100644
index 0000000000..d053384cbd
--- /dev/null
+++ b/packages/@vuepress/plugin-search/match-query.js
@@ -0,0 +1,42 @@
+
+import get from 'lodash/get'
+
+export default (query, page, additionalStr = null) => {
+  let domain = get(page, 'title', '')
+
+  if (get(page, 'frontmatter.tags')) {
+    domain += ` ${page.frontmatter.tags.join(' ')}`
+  }
+
+  if (additionalStr) {
+    domain += ` ${additionalStr}`
+  }
+
+  return matchTest(query, domain)
+}
+
+const matchTest = (query, domain) => {
+  const escapeRegExp = str => str.replace(/[-/\\^$*+?.()|[\]{}]/g, '\\$&')
+
+  const words = query
+    .split(/\s+/g)
+    .map(str => str.trim())
+    .filter(str => !!str)
+  const hasTrailingSpace = query.endsWith(' ')
+  const searchRegex = new RegExp(
+    words
+      .map((word, index) => {
+        if (words.length === index + 1 && !hasTrailingSpace) {
+          // The last word - ok with the word being "startswith"-like
+          return `(?=.*\\b${escapeRegExp(word)})`
+        } else {
+          // Not the last word - expect the whole word exactly
+          return `(?=.*\\b${escapeRegExp(word)}\\b)`
+        }
+      })
+      .join('') + '.+',
+    'gi'
+  )
+  return searchRegex.test(domain)
+}
+
diff --git a/packages/docs/docs/guide/frontmatter.md b/packages/docs/docs/guide/frontmatter.md
index c158482049..1b3f0f5ce4 100644
--- a/packages/docs/docs/guide/frontmatter.md
+++ b/packages/docs/docs/guide/frontmatter.md
@@ -49,6 +49,13 @@ lang = "en-US"
 
 Title of current page.
 
+### tags
+
+- Type: `array`
+- Default: `undefined`
+
+You can use tags to improve [built-in search](/theme/default-theme-config.html#built-in-search).
+
 ### lang
 
 - Type: `string`
diff --git a/packages/docs/docs/theme/default-theme-config.md b/packages/docs/docs/theme/default-theme-config.md
index 7e4a7a73cd..d700d8482e 100644
--- a/packages/docs/docs/theme/default-theme-config.md
+++ b/packages/docs/docs/theme/default-theme-config.md
@@ -357,10 +357,19 @@ search: false
 ```
 
 ::: tip
-Built-in Search only builds index from the title, `h2` and `h3` headers, if you need full text search, you can use [Algolia DocSearch](#algolia-docsearch).
+Built-in Search only builds index from the title, `h2` and `h3` headers and any tags added with `YAML front matter` as shown below, if you need full text search, you can use [Algolia Search](#algolia-search).
 :::
 
-### Algolia DocSearch
+```yaml
+---
+tags: 
+  - configuration
+  - theme
+  - indexing
+---
+```
+
+### Algolia Search
 
 The `themeConfig.algolia` option allows you to use [Algolia DocSearch](https://community.algolia.com/docsearch/) to replace the simple built-in search. To enable it, you need to provide at least `apiKey` and `indexName`: