fix(5594): Cyrillic has different typo tolerance due to byte counting bug

crates/meilisearch/tests/search/locales.rs

@@ -147,23 +147,20 @@ async fn simple_search() {
         .search(
             json!({"q": "進撃", "locales": ["jpn"], "attributesToRetrieve": ["id"]}),
             |response, code| {
-                snapshot!(response, @r###"
+                snapshot!(response, @r#"
                 {
                   "hits": [
                     {
                       "id": 852
-                    },
-                    {
-                      "id": 853
                     }
                   ],
                   "query": "進撃",
                   "processingTimeMs": "[duration]",
                   "limit": 20,
                   "offset": 0,
-                  "estimatedTotalHits": 2
+                  "estimatedTotalHits": 1
                 }
-                "###);
+                "#);
                 snapshot!(code, @"200 OK");
             },
         )
@@ -172,23 +169,20 @@ async fn simple_search() {
     // chinese
     index
         .search(json!({"q": "进击", "attributesToRetrieve": ["id"]}), |response, code| {
-            snapshot!(response, @r###"
+            snapshot!(response, @r#"
             {
               "hits": [
                 {
                   "id": 853
-                },
-                {
-                  "id": 852
                 }
               ],
               "query": "进击",
               "processingTimeMs": "[duration]",
               "limit": 20,
               "offset": 0,
-              "estimatedTotalHits": 2
+              "estimatedTotalHits": 1
             }
-            "###);
+            "#);
             snapshot!(code, @"200 OK");
         })
         .await;

crates/milli/src/search/new/query_term/parse_query.rs

@@ -202,11 +202,11 @@ pub fn number_of_typos_allowed<'ctx>(
 
     Ok(Box::new(move |word: &str| {
         if !authorize_typos
-            || word.len() < min_len_one_typo as usize
+            || word.chars().count() < min_len_one_typo as usize
             || exact_words.as_ref().is_some_and(|fst| fst.contains(word))
         {
             0
-        } else if word.len() < min_len_two_typos as usize {
+        } else if word.chars().count() < min_len_two_typos as usize {
             1
         } else {
             2
@@ -380,4 +380,62 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn test_unicode_typo_tolerance_fixed() -> Result<()> {
+        let temp_index = temp_index_with_documents();
+        let rtxn = temp_index.read_txn()?;
+        let ctx = SearchContext::new(&temp_index, &rtxn)?;
+
+        let nbr_typos = number_of_typos_allowed(&ctx)?;
+
+        // ASCII word "doggy" (5 chars, 5 bytes)
+        let ascii_word = "doggy";
+        let ascii_typos = nbr_typos(ascii_word);
+
+        // Cyrillic word "собак" (5 chars, 10 bytes)
+        let cyrillic_word = "собак";
+        let cyrillic_typos = nbr_typos(cyrillic_word);
+
+        // Both words have 5 characters, so they should have the same typo tolerance
+        assert_eq!(
+            ascii_typos, cyrillic_typos,
+            "Words with same character count should get same typo tolerance"
+        );
+
+        // With default settings (oneTypo=5, twoTypos=9), 5-char words should get 1 typo
+        assert_eq!(ascii_typos, 1, "5-character word should get 1 typo tolerance");
+        assert_eq!(cyrillic_typos, 1, "5-character word should get 1 typo tolerance");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_various_unicode_scripts() -> Result<()> {
+        let temp_index = temp_index_with_documents();
+        let rtxn = temp_index.read_txn()?;
+        let ctx = SearchContext::new(&temp_index, &rtxn)?;
+
+        let nbr_typos = number_of_typos_allowed(&ctx)?;
+
+        // Let's use 5-character words for consistent testing
+        let five_char_words = vec![
+            ("doggy", "ASCII"),    // 5 chars, 5 bytes
+            ("café!", "Accented"), // 5 chars, 7 bytes
+            ("собак", "Cyrillic"), // 5 chars, 10 bytes
+        ];
+
+        let expected_typos = 1; // With default settings, 5-char words get 1 typo
+
+        for (word, script) in five_char_words {
+            let typos = nbr_typos(word);
+            assert_eq!(
+                typos, expected_typos,
+                "{} word '{}' should get {} typo(s)",
+                script, word, expected_typos
+            );
+        }
+
+        Ok(())
+    }
 }