fzf: return default Match if query is empty

src/algos/fzf/distance.rs

@@ -4,6 +4,13 @@ use super::{Distance, Score};
 #[derive(Debug, Clone, Copy, Ord, PartialOrd, Eq, PartialEq)]
 pub struct FzfDistance(Distance);
 
+impl Default for FzfDistance {
+    #[inline]
+    fn default() -> Self {
+        Self::from_score(0)
+    }
+}
+
 impl FzfDistance {
     /// TODO: docs
     #[inline]

src/algos/fzf/v1.rs

@@ -89,7 +89,7 @@ impl Metric for FzfV1 {
         candidate: &str,
     ) -> Option<Match<Self::Distance>> {
         if query.is_empty() {
-            return None;
+            return Some(Match::default());
         }
 
         let is_candidate_ascii = candidate.is_ascii();

src/algos/fzf/v2.rs

@@ -90,7 +90,7 @@ impl Metric for FzfV2 {
         candidate: &str,
     ) -> Option<Match<Self::Distance>> {
         if query.is_empty() {
-            return None;
+            return Some(Match::default());
         }
 
         let is_candidate_ascii = candidate.is_ascii();

src/match.rs

@@ -3,6 +3,7 @@ use core::ops::Range;
 use crate::MatchedRanges;
 
 /// TODO: docs
+#[derive(Default)]
 pub struct Match<D: Copy> {
     /// TODO: docs
     distance: D,

tests/fzf_common.rs

@@ -4,9 +4,14 @@ use norm::fzf::{bonus, penalty};
 use norm::CaseSensitivity;
 use CaseSensitivity::*;
 
-pub fn empty_query<F: Fzf>() {
+pub fn upstream_empty<F: Fzf>() {
     let (_, m) = fzf::<F>(Insensitive, "", "foo");
-    assert!(m.is_none());
+
+    let m = m.unwrap();
+
+    assert_eq!(m.distance().into_score(), 0);
+
+    assert!(m.matched_ranges().is_empty());
 }
 
 pub fn upstream_fuzzy_1<F: Fzf>() {

tests/fzf_v1.rs

@@ -6,8 +6,8 @@ use fzf_common as common;
 use norm::fzf::FzfV1;
 
 #[test]
-fn fzf_v1_empty_query() {
-    common::empty_query::<FzfV1>();
+fn fzf_v1_upstream_empty() {
+    common::upstream_empty::<FzfV1>();
 }
 
 #[test]

tests/fzf_v2.rs

@@ -8,8 +8,8 @@ use norm::fzf::{bonus, FzfParser, FzfV2};
 use norm::{CaseSensitivity, Metric};
 
 #[test]
-fn fzf_v2_empty_query() {
-    common::empty_query::<FzfV2>();
+fn fzf_v2_upstream_empty_1() {
+    common::upstream_empty::<FzfV2>();
 }
 
 #[test]