fzf: return a null score if pattern is empty

src/algos/fzf/common.rs

@@ -110,6 +110,10 @@ pub(super) fn exact_match(
     with_matched_ranges: bool,
     matched_ranges: &mut MatchedRanges,
 ) -> Option<Score> {
+    if pattern.is_empty() {
+        return Some(0);
+    }
+
     // TODO: docs
     let mut best_bonus: i64 = -1;
 
@@ -209,6 +213,10 @@ pub(super) fn prefix_match(
     with_matched_ranges: bool,
     matched_ranges: &mut MatchedRanges,
 ) -> Option<Score> {
+    if pattern.is_empty() {
+        return Some(0);
+    }
+
     let mut pattern_chars = pattern.chars();
 
     let ignored_leading_spaces =
@@ -256,6 +264,10 @@ pub(super) fn suffix_match(
     with_matched_ranges: bool,
     matched_ranges: &mut MatchedRanges,
 ) -> Option<Score> {
+    if pattern.is_empty() {
+        return Some(0);
+    }
+
     let mut pattern_chars = pattern.chars().rev();
 
     let up_to_ignored_spaces = candidate.len()
@@ -305,6 +317,10 @@ pub(super) fn equal_match(
     with_matched_ranges: bool,
     matched_ranges: &mut MatchedRanges,
 ) -> Option<Score> {
+    if pattern.is_empty() {
+        return Some(0);
+    }
+
     let ignored_leading_spaces =
         ignored_candidate_leading_spaces(pattern, candidate)?;
 

src/algos/fzf/v1.rs

@@ -172,6 +172,10 @@ pub(super) fn fzf_v1(
     is_candidate_ascii: bool,
     matched_ranges: &mut MatchedRanges,
 ) -> Option<Score> {
+    if pattern.is_empty() {
+        return Some(0);
+    }
+
     let range_forward = forward_pass(
         pattern,
         candidate,

src/algos/fzf/v2.rs

@@ -173,6 +173,10 @@ pub(super) fn fzf_v2(
     (slab, is_candidate_ascii): (&mut V2Slab, bool),
     ranges: &mut MatchedRanges,
 ) -> Option<Score> {
+    if pattern.is_empty() {
+        return Some(0);
+    }
+
     let (matches, last_match_offset) = matches(
         &mut slab.matched_indices,
         pattern,

tests/fzf_v2.rs

@@ -237,3 +237,16 @@ fn fzf_v2_score_1() {
 
     assert_eq!(mach.matched_ranges().sorted(), [0..5]);
 }
+
+#[test]
+fn fzf_v2_score_2() {
+    let mut fzf = FzfV2::new()
+        .with_case_sensitivity(CaseSensitivity::Sensitive)
+        .with_matched_ranges(true);
+
+    let mut parser = FzfParser::new();
+
+    let mach = fzf.distance(parser.parse("!$"), "$$2");
+
+    assert!(mach.is_none());
+}