Improve support for completing within quotes. (#2474)

We ensure the partially cimpleted item doesn't include the end quote. We also
ensure that the appropriate span is replaced, not just the suggested position up
to the cursor position.

crates/nu-cli/src/shell/completer.rs

@@ -63,7 +63,7 @@ impl NuCompleter {
 
                             let partial = if let Some(quote_char) = quote_char {
                                 if partial.ends_with(quote_char) {
-                                    &partial[..partial.len()]
+                                    &partial[..partial.len() - 1]
                                 } else {
                                     partial
                                 }

crates/nu-cli/src/shell/helper.rs

@@ -52,6 +52,11 @@ impl rustyline::completion::Completer for Helper {
         let ctx = completion::Context::new(&self.context);
         Ok(self.completer.complete(line, pos, &ctx))
     }
+
+    fn update(&self, line: &mut rustyline::line_buffer::LineBuffer, start: usize, elected: &str) {
+        let end = (start + elected.len()).min(line.len());
+        line.replace(start..end, elected)
+    }
 }
 
 impl rustyline::hint::Hinter for Helper {