There is no need for to be rude and disrespectful. Please change the title of this issue to something that is more respectful to the nushell contributors.

The fuzzy matcher returns a number based on how well the given string matches, but that number is not used anywhere to order the results. This often means even verbatim substrings not found in any other filename do not appear at the top of the suggestions.

I concur on this: the fuzzy finder matches without taking into account the score often give very surprising results.

As a temporary fix, I have replaced the fuzzy matching by a substring search akin to what I had in zsh. It stands between the prefix algorithm and the fuzzy one in terms of flexibility.

diff --git a/crates/nu-cli/src/completions/completion_options.rs b/crates/nu-cli/src/completions/completion_options.rs
index a414aafed..c1eaf540c 100644
--- a/crates/nu-cli/src/completions/completion_options.rs
+++ b/crates/nu-cli/src/completions/completion_options.rs
@@ -1,6 +1,7 @@
 use fuzzy_matcher::{skim::SkimMatcherV2, FuzzyMatcher};
 use nu_parser::trim_quotes_str;
 use nu_protocol::CompletionAlgorithm;
+use std::borrow::Borrow;
 use std::fmt::Display;

 #[derive(Copy, Clone)]
@@ -33,10 +34,7 @@ impl MatchAlgorithm {
         let needle = trim_quotes_str(needle);
         match *self {
             MatchAlgorithm::Prefix => haystack.starts_with(needle),
-            MatchAlgorithm::Fuzzy => {
-                let matcher = SkimMatcherV2::default();
-                matcher.fuzzy_match(haystack, needle).is_some()
-            }
+            MatchAlgorithm::Fuzzy => haystack.contains(needle),
         }
     }

@@ -46,10 +44,10 @@ impl MatchAlgorithm {
             MatchAlgorithm::Prefix => haystack.starts_with(needle),
             MatchAlgorithm::Fuzzy => {
                 let haystack_str = String::from_utf8_lossy(haystack);
+                let haystack_str: &str = haystack_str.borrow();
                 let needle_str = String::from_utf8_lossy(needle);

-                let matcher = SkimMatcherV2::default();
-                matcher.fuzzy_match(&haystack_str, &needle_str).is_some()
+                haystack_str.contains(&*needle_str)
             }
         }
     }

To properly fix the fuzzy matching, one needs to:

• decide on a score threshold and/or
• implement result ordering, taking into account the score. See also Completion algorithm: try prefix, fallback to fuzzy if, and only if, prefix gives no results #11211

I think there would be also value in adding a completions.algorithm = "substring" option, corresponding to the above. I'm happy to send a PR if you wish.

@cpg314 I believe you can already do completions based on substrings by using the prefix algorithm and then setting positional to false. I agree, though, an explicit substring option would be nicer than having a separate positional option (since it doesn't seem all that useful for fuzzy matching)

Edit: positional: true is only an option when custom completions are provided, not for all completions.

From playing around with version 0.101.0, issues 1) and 2) appear to have been fixed, only 3) remains.

The reproducible example panic is resolved by nushell/reedline#886 as shipped with #15310

But there remains a case for non-prefix matches that @ysthakur is trying to address with nushell/reedline#887

This is triggered if the file doesn't start with the searched for character

e.g.

touch æææa
open 'a<TAB>