From b167058028950867feeac42873adaf1b6b7bebf1 Mon Sep 17 00:00:00 2001
From: Chen Xu <chenyexu@gmail.com>
Date: Thu, 19 Mar 2020 04:19:32 -0700
Subject: [PATCH] Fix prefix option for FuzzyTermQuery (#797)

* Fix prefix option for FuzzyTermQuery

* Update changelog
---
 CHANGELOG.md             |  4 ++++
 src/query/fuzzy_query.rs | 18 +++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 90a9e4edf..0ec34d74c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+Tantivy 0.13.0
+======================
+- Bugfix in `FuzzyTermQuery` not matching terms by prefix when it should (@Peachball)
+
 Tantivy 0.12.0
 ======================
 - Removing static dispatch in tokenizers for simplicity. (#762)
diff --git a/src/query/fuzzy_query.rs b/src/query/fuzzy_query.rs
index 543a0980f..3bff39d50 100644
--- a/src/query/fuzzy_query.rs
+++ b/src/query/fuzzy_query.rs
@@ -106,7 +106,11 @@ impl FuzzyTermQuery {
         match LEV_BUILDER.get(&(self.distance, false)) {
             // Unwrap the option and build the Ok(AutomatonWeight)
             Some(automaton_builder) => {
-                let automaton = automaton_builder.build_dfa(self.term.text());
+                let automaton = if self.prefix {
+                    automaton_builder.build_prefix_dfa(self.term.text())
+                } else {
+                    automaton_builder.build_dfa(self.term.text())
+                };
                 Ok(AutomatonWeight::new(self.term.field(), automaton))
             }
             None => Err(InvalidArgument(format!(
@@ -166,5 +170,17 @@ mod test {
             let (score, _) = top_docs[0];
             assert_nearly_equals(1f32, score);
         }
+
+        {
+            let term = Term::from_field_text(country_field, "jap");
+
+            let fuzzy_query = FuzzyTermQuery::new_prefix(term, 1, true);
+            let top_docs = searcher
+                .search(&fuzzy_query, &TopDocs::with_limit(2))
+                .unwrap();
+            assert_eq!(top_docs.len(), 1, "Expected only 1 document");
+            let (score, _) = top_docs[0];
+            assert_nearly_equals(1f32, score);
+        }
     }
 }