fix: unknown span for special variables $in/$it (#14789)

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# Description
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This PR addresses the issue of inconsistent spans of special variables
of `$in/$in`, as discussed in
https://github.com/nushell/nushell/pull/14770#discussion_r1908729364.

Instead of making the `declaration_span` to be Option, which will cause
too many changes that we may want to avoid, this PR set the spans to be
`unknown`.


# User-Facing Changes
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No

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crates/nu-lsp/src/symbols.rs

@@ -118,10 +118,6 @@ impl SymbolCache {
                 }
                 let range = span_to_range(&span, doc, doc_span.start);
                 let name = doc.get_content(Some(range));
-                // TODO: better way to filter closures with type any
-                if name.contains('\r') || name.contains('\n') || name.contains('{') {
-                    return None;
-                }
                 Some(Symbol {
                     name: name.to_string(),
                     kind: SymbolKind::VARIABLE,
@@ -343,6 +339,29 @@ mod tests {
             .unwrap()
     }
 
+    #[test]
+    // for variable `$in/$it`, should not appear in symbols
+    fn document_symbol_special_variables() {
+        let (client_connection, _recv) = initialize_language_server();
+
+        let mut script = fixtures();
+        script.push("lsp");
+        script.push("symbols");
+        script.push("span.nu");
+        let script = path_to_uri(&script);
+
+        open_unchecked(&client_connection, script.clone());
+
+        let resp = document_symbol_test(&client_connection, script.clone());
+        let result = if let Message::Response(response) = resp {
+            response.result
+        } else {
+            panic!()
+        };
+
+        assert_json_eq!(result, serde_json::json!([]));
+    }
+
     #[test]
     fn document_symbol_basic() {
         let (client_connection, _recv) = initialize_language_server();

crates/nu-parser/src/parser.rs

@@ -3435,7 +3435,7 @@ pub fn parse_full_signature(working_set: &mut StateWorkingSet, spans: &[Span]) -
 }
 
 pub fn parse_row_condition(working_set: &mut StateWorkingSet, spans: &[Span]) -> Expression {
-    let var_id = working_set.add_variable(b"$it".to_vec(), Span::concat(spans), Type::Any, false);
+    let var_id = working_set.add_variable(b"$it".to_vec(), Span::unknown(), Type::Any, false);
     let expression = parse_math_expression(working_set, spans, Some(var_id));
     let span = Span::concat(spans);
 
@@ -6633,7 +6633,7 @@ fn wrap_expr_with_collect(working_set: &mut StateWorkingSet, expr: Expression) -
 
     // IN_VARIABLE_ID should get replaced with a unique variable, so that we don't have to
     // execute as a closure
-    let var_id = working_set.add_variable(b"$in".into(), expr.span, Type::Any, false);
+    let var_id = working_set.add_variable(b"$in".into(), Span::unknown(), Type::Any, false);
     let mut expr = expr.clone();
     expr.replace_in_variable(working_set, var_id);
 

tests/fixtures/lsp/symbols/span.nu

@@ -0,0 +1,3 @@
+ls | where name != foo
+ls | each { $in }
+ls | $in.name