multiline validation

crates/nu-cli/src/lib.rs

@@ -1,7 +1,9 @@
 mod completions;
 mod errors;
 mod syntax_highlight;
+mod validation;
 
 pub use completions::NuCompleter;
 pub use errors::report_error;
 pub use syntax_highlight::NuHighlighter;
+pub use validation::NuValidator;

crates/nu-cli/src/validation.rs

@@ -0,0 +1,23 @@
+use std::{cell::RefCell, rc::Rc};
+
+use nu_parser::{parse, ParseError};
+use nu_protocol::engine::{EngineState, StateWorkingSet};
+use reedline::{ValidationResult, Validator};
+
+pub struct NuValidator {
+    pub engine_state: Rc<RefCell<EngineState>>,
+}
+
+impl Validator for NuValidator {
+    fn validate(&self, line: &str) -> ValidationResult {
+        let engine_state = self.engine_state.borrow();
+        let mut working_set = StateWorkingSet::new(&*engine_state);
+        let (_, err) = parse(&mut working_set, None, line.as_bytes(), false);
+
+        if matches!(err, Some(ParseError::UnexpectedEof(..))) {
+            ValidationResult::Incomplete
+        } else {
+            ValidationResult::Complete
+        }
+    }
+}