Merge #1813

1813: Apply highlight tags on numbers in the formatted search result output r=irevoire a=Jhnbrn90

This is my first ever Rust related PR. 

As described in #1758, I've attempted to highlighting numbers correctly under the `_formatted` key.

Additionally, I added a test which should assert appropriate highlighting. 

I'm open to suggestions and improvements. 


Co-authored-by: John Braun <john@brn.email>

meilisearch-lib/src/index/search.rs

@@ -554,6 +554,11 @@ impl<'a, A: AsRef<[u8]>> Formatter<'a, A> {
                     })
                     .collect(),
             ),
+            Value::Number(number) => {
+                let number_string_value =
+                    self.format_string(number.to_string(), matcher, format_options);
+                Value::String(number_string_value)
+            }
             value => value,
         }
     }
@@ -788,6 +793,92 @@ mod test {
         assert_eq!(value["author"], "J. R. R. Tolkien");
     }
 
+    #[test]
+    fn formatted_with_highlight_in_number() {
+        let stop_words = fst::Set::default();
+        let mut config = AnalyzerConfig::default();
+        config.stop_words(&stop_words);
+        let analyzer = Analyzer::new(config);
+        let formatter = Formatter::new(&analyzer, (String::from("<em>"), String::from("</em>")));
+
+        let mut fields = FieldsIdsMap::new();
+        let title = fields.insert("title").unwrap();
+        let author = fields.insert("author").unwrap();
+        let publication_year = fields.insert("publication_year").unwrap();
+
+        let mut buf = Vec::new();
+        let mut obkv = obkv::KvWriter::new(&mut buf);
+
+        obkv.insert(
+            title,
+            Value::String("The Hobbit".into()).to_string().as_bytes(),
+        )
+        .unwrap();
+
+        obkv.finish().unwrap();
+        obkv = obkv::KvWriter::new(&mut buf);
+
+        obkv.insert(
+            author,
+            Value::String("J. R. R. Tolkien".into())
+                .to_string()
+                .as_bytes(),
+        )
+        .unwrap();
+        obkv.finish().unwrap();
+
+        obkv = obkv::KvWriter::new(&mut buf);
+
+        obkv.insert(
+            publication_year,
+            Value::Number(1937.into()).to_string().as_bytes(),
+        )
+        .unwrap();
+
+        obkv.finish().unwrap();
+
+        let obkv = obkv::KvReader::new(&buf);
+
+        let mut formatted_options = BTreeMap::new();
+        formatted_options.insert(
+            title,
+            FormatOptions {
+                highlight: false,
+                crop: None,
+            },
+        );
+        formatted_options.insert(
+            author,
+            FormatOptions {
+                highlight: false,
+                crop: None,
+            },
+        );
+        formatted_options.insert(
+            publication_year,
+            FormatOptions {
+                highlight: true,
+                crop: None,
+            },
+        );
+
+        let mut matching_words = BTreeMap::new();
+        matching_words.insert("1937", Some(4));
+
+        let value = format_fields(
+            &fields,
+            obkv,
+            &formatter,
+            &matching_words,
+            &formatted_options,
+        )
+        .unwrap();
+
+        assert_eq!(value["title"], "The Hobbit");
+        assert_eq!(value["author"], "J. R. R. Tolkien");
+        assert_eq!(value["publication_year"], "<em>1937</em>");
+    }
+
     /// https://github.com/meilisearch/MeiliSearch/issues/1368
     #[test]
     fn formatted_with_highlight_emoji() {