From 0d6a70bd0f93f10a493f4c99aaab2d02ddcb8ad3 Mon Sep 17 00:00:00 2001
From: seb-bl <31244011+seb-bl@users.noreply.github.com>
Date: Sun, 10 May 2020 10:44:24 +0200
Subject: [PATCH] Interface::run returns a Cow<'a>

Changed `Interface::run` to return a `Cow` with the lifetime of the borrowed slice of strings.

The `Owned` case occurs when the search does not match anything. In that case, the search string is taken out of the `Interface` and replaced by an empty string.

Using a `Cow` with the lifetime of the given strings allows to drop the `Interface` struct after a run, without needing to clone the returned `&str` to keep the result. It also allows the caller to know whether the result is from the given list, or comes from a search that had no match.
---
 src/interface.rs | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/interface.rs b/src/interface.rs
index eea8c86..153733a 100644
--- a/src/interface.rs
+++ b/src/interface.rs
@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::io::{self, Write, BufWriter};
 
 use super::{MatchWithPositions, match_and_score_with_positions};
@@ -57,8 +58,9 @@ impl<'a> Interface<'a> {
         }
     }
 
-    // Runs the Interface, returning either the final selection, or an error
-    pub fn run(&mut self) -> Result<&str, Error> {
+    // Runs the Interface, returning either the final selection, the final
+    // search string if nothing matches, or an error
+    pub fn run(&mut self) -> Result<Cow<'a, str>, Error> {
         self.filter_matches();
         self.render()?;
 
@@ -108,7 +110,7 @@ impl<'a> Interface<'a> {
         }
 
         self.reset()?;
-        Ok(self.result())
+        Ok(self.take_result())
     }
 
     // Matches and scores `lines` by `search`, sorting the result
@@ -205,10 +207,13 @@ impl<'a> Interface<'a> {
         Ok(())
     }
 
-    fn result(&mut self) -> &str {
+    // Get a reference to the selected item, or take the search (and replace it with empty)
+    fn take_result(&mut self) -> Cow<'a, str> {
         self.matches.iter().
             nth(self.selected).
-            map(|choice| choice.0).
-            unwrap_or(&self.search)
+            map(|choice| Cow::Borrowed(choice.0)).
+            unwrap_or_else(||
+                Cow::Owned(std::mem::take(&mut self.search))
+            )
     }
 }