Fix spans passed to external_completer (#11008)

close #10973

crates/nu-cli/tests/completions.rs

@@ -59,6 +59,29 @@ fn extern_completer() -> NuCompleter {
     NuCompleter::new(std::sync::Arc::new(engine), stack)
 }
 
+#[fixture]
+fn custom_completer() -> NuCompleter {
+    // Create a new engine
+    let (dir, _, mut engine, mut stack) = new_engine();
+
+    // Add record value as example
+    let record = r#"
+        let external_completer = {|spans| 
+            $spans
+        }
+
+        $env.config.completions.external = {
+            enable: true
+            max_results: 100
+            completer: $external_completer
+        }
+    "#;
+    assert!(support::merge_input(record.as_bytes(), &mut engine, &mut stack, dir).is_ok());
+
+    // Instantiate a new completer
+    NuCompleter::new(std::sync::Arc::new(engine), stack)
+}
+
 #[test]
 fn variables_dollar_sign_with_varialblecompletion() {
     let (_, _, engine, stack) = new_engine();
@@ -938,6 +961,34 @@ fn extern_complete_flags(mut extern_completer: NuCompleter) {
     match_suggestions(expected, suggestions);
 }
 
+#[rstest]
+fn custom_completer_triggers_cursor_before_word(mut custom_completer: NuCompleter) {
+    let suggestions = custom_completer.complete("cmd foo  bar", 8);
+    let expected: Vec<String> = vec!["cmd".into(), "foo".into(), "".into()];
+    match_suggestions(expected, suggestions);
+}
+
+#[rstest]
+fn custom_completer_triggers_cursor_on_word_left_boundary(mut custom_completer: NuCompleter) {
+    let suggestions = custom_completer.complete("cmd foo bar", 8);
+    let expected: Vec<String> = vec!["cmd".into(), "foo".into(), "".into()];
+    match_suggestions(expected, suggestions);
+}
+
+#[rstest]
+fn custom_completer_triggers_cursor_next_to_word(mut custom_completer: NuCompleter) {
+    let suggestions = custom_completer.complete("cmd foo bar", 11);
+    let expected: Vec<String> = vec!["cmd".into(), "foo".into(), "bar".into()];
+    match_suggestions(expected, suggestions);
+}
+
+#[rstest]
+fn custom_completer_triggers_cursor_after_word(mut custom_completer: NuCompleter) {
+    let suggestions = custom_completer.complete("cmd foo bar ", 12);
+    let expected: Vec<String> = vec!["cmd".into(), "foo".into(), "bar".into(), "".into()];
+    match_suggestions(expected, suggestions);
+}
+
 #[ignore = "was reverted, still needs fixing"]
 #[rstest]
 fn alias_offset_bug_7648() {