feat(docsearch): add search suggestions

src/DocSearch.tsx

@@ -51,6 +51,8 @@ export function DocSearch({
     getInputProps,
     getMenuProps,
     getItemProps,
+    setQuery,
+    refresh,
   } = React.useMemo(
     () =>
       createAutocomplete<
@@ -66,7 +68,7 @@ export function DocSearch({
         onStateChange({ state }) {
           setState(state as any);
         },
-        getSources({ query }) {
+        getSources({ query, state, setContext }) {
           return getAlgoliaHits({
             searchClient,
             queries: [
@@ -117,6 +119,14 @@ export function DocSearch({
             });
             const sources = groupBy(formattedHits, hit => hit.hierarchy.lvl0);
 
+            // We store the `lvl0`s to display them as search suggestions
+            // in the “no results“ screen.
+            if (state.context.searchSuggestions === undefined) {
+              setContext({
+                searchSuggestions: Object.keys(sources),
+              });
+            }
+
             return Object.values<DocSearchHit[]>(sources).map(items => {
               return {
                 onSelect() {
@@ -220,9 +230,12 @@ export function DocSearch({
 
         <div className="DocSearch-Dropdown" ref={dropdownRef}>
           <Dropdown
+            inputRef={inputRef}
             state={state}
             getMenuProps={getMenuProps}
             getItemProps={getItemProps}
+            setQuery={setQuery}
+            refresh={refresh}
           />
         </div>
 

src/Dropdown/Dropdown.tsx

@@ -14,6 +14,9 @@ interface DropdownProps {
   state: AutocompleteState<InternalDocSearchHit>;
   getMenuProps: GetMenuProps;
   getItemProps: GetItemProps<InternalDocSearchHit, React.MouseEvent>;
+  setQuery(value: string): void;
+  refresh(): Promise<void>;
+  inputRef: React.MutableRefObject<HTMLInputElement>;
 }
 
 export function Dropdown(props: DropdownProps) {
@@ -25,7 +28,14 @@ export function Dropdown(props: DropdownProps) {
     props.state.status === 'idle' &&
     props.state.suggestions.every(source => source.items.length === 0)
   ) {
-    return <NoResults query={props.state.query} />;
+    return (
+      <NoResults
+        setQuery={props.setQuery}
+        refresh={props.refresh}
+        state={props.state}
+        inputRef={props.inputRef}
+      />
+    );
   }
 
   return (

src/NoResults/NoResults.tsx

@@ -1,12 +1,58 @@
 import React from 'react';
+import { AutocompleteState } from '@francoischalifour/autocomplete-core';
 
 interface NoResultsProps {
-  query: string;
+  state: AutocompleteState<any>;
+  setQuery(value: string): void;
+  refresh(): Promise<void>;
+  inputRef: React.MutableRefObject<HTMLInputElement>;
 }
 
 export function NoResults(props: NoResultsProps) {
-  return <div className="DocSearch-NoResults">
-    <div className="Docsearch-Hit-title">No results for “{props.query}“.</div>
-    <div className="DocSearch-Label">Try another search or if you believe this query should lead to actual results, please let us know with a <a href="">GitHub issue</a>.</div>
-  </div>;
+  return (
+    <div className="DocSearch-NoResults">
+      <p className="Docsearch-Hit-title">
+        No results for “{props.state.query}“.
+      </p>
+
+      <p>
+        Try searching for{' '}
+        {(props.state.context.searchSuggestions as string[])
+          .slice(0, 3)
+          .reduce<React.ReactNode[]>(
+            (acc, search) => [
+              ...acc,
+              acc.length > 0 ? ', ' : '',
+              '“',
+              <button
+                className="DocSearch-Link"
+                key={search}
+                onClick={() => {
+                  props.setQuery(search.toLowerCase() + ' ');
+                  props.refresh();
+                  props.inputRef.current.focus();
+                }}
+              >
+                {search}
+              </button>,
+              '“',
+            ],
+            []
+          )}
+        .
+      </p>
+
+      <p className="DocSearch-Label">
+        If you believe this query should return results, please{' '}
+        <a
+          href="https://github.com/algolia/docsearch-configs/issues/new?template=Missing_results.md"
+          target="_blank"
+          rel="noopener noreferrer"
+        >
+          let us know on GitHub
+        </a>
+        .
+      </p>
+    </div>
+  );
 }

src/style.css

@@ -169,6 +169,17 @@ html[data-theme='dark'] {
   text-decoration: none;
 }
 
+.DocSearch-Link {
+  appearance: none;
+  background: none;
+  border: none;
+  color: var(--docsearch-highlight-color);
+  cursor: pointer;
+  font: inherit;
+  margin: 0;
+  padding: 0;
+}
+
 .DocSearch-Modal {
   position: relative;
   flex-direction: column;