fix(repl): improve validator to mark more code as incomplete (#17443)

Closes #17442

cli/tools/repl/editor.rs

@@ -235,17 +235,34 @@ impl Validator for EditorHelper {
     &self,
     ctx: &mut ValidationContext,
   ) -> Result<ValidationResult, ReadlineError> {
+    Ok(validate(ctx.input()))
+  }
+}
+
+fn validate(input: &str) -> ValidationResult {
+  let line_info = text_lines::TextLines::new(input);
   let mut stack: Vec<Token> = Vec::new();
   let mut in_template = false;
+  let mut div_token_count_on_current_line = 0;
+  let mut last_line_index = 0;
 
-    for item in deno_ast::lex(ctx.input(), deno_ast::MediaType::TypeScript) {
+  for item in deno_ast::lex(input, deno_ast::MediaType::TypeScript) {
+    let current_line_index = line_info.line_index(item.range.start);
+    if current_line_index != last_line_index {
+      div_token_count_on_current_line = 0;
+      last_line_index = current_line_index;
+    }
     if let deno_ast::TokenOrComment::Token(token) = item.inner {
       match token {
         Token::BinOp(BinOpToken::Div)
         | Token::AssignOp(AssignOp::DivAssign) => {
           // it's too complicated to write code to detect regular expression literals
-            // which are no longer tokenized, so if a `/` or `/=` happens, then we bail
-            return Ok(ValidationResult::Valid(None));
+          // which are no longer tokenized, so if a `/` or `/=` happens twice on the same
+          // line, then we bail
+          div_token_count_on_current_line += 1;
+          if div_token_count_on_current_line >= 2 {
+            return ValidationResult::Valid(None);
+          }
         }
         Token::BackQuote => in_template = !in_template,
         Token::LParen
@@ -259,15 +276,15 @@ impl Validator for EditorHelper {
             | (Some(Token::LBrace), Token::RBrace)
             | (Some(Token::DollarLBrace), Token::RBrace) => {}
             (Some(left), _) => {
-                return Ok(ValidationResult::Invalid(Some(format!(
+              return ValidationResult::Invalid(Some(format!(
                 "Mismatched pairs: {:?} is not properly closed",
                 left
-                ))))
+              )))
             }
             (None, _) => {
               // While technically invalid when unpaired, it should be V8's task to output error instead.
               // Thus marked as valid with no info.
-                return Ok(ValidationResult::Valid(None));
+              return ValidationResult::Valid(None);
             }
           }
         }
@@ -278,7 +295,7 @@ impl Validator for EditorHelper {
             _ => {
               // If it failed parsing, it should be V8's task to output error instead.
               // Thus marked as valid with no info.
-                return Ok(ValidationResult::Valid(None));
+              return ValidationResult::Valid(None);
             }
           }
         }
@@ -288,11 +305,10 @@ impl Validator for EditorHelper {
   }
 
   if !stack.is_empty() || in_template {
-      return Ok(ValidationResult::Incomplete);
+    return ValidationResult::Incomplete;
   }
 
-    Ok(ValidationResult::Valid(None))
-  }
+  ValidationResult::Valid(None)
 }
 
 impl Highlighter for EditorHelper {
@@ -512,3 +528,24 @@ impl ConditionalEventHandler for TabEventHandler {
     }
   }
 }
+
+#[cfg(test)]
+mod test {
+  use rustyline::validate::ValidationResult;
+
+  use super::validate;
+
+  #[test]
+  fn validate_only_one_forward_slash_per_line() {
+    let code = r#"function test(arr){
+if( arr.length <= 1) return arr.map(a => a / 2)
+let left = test( arr.slice( 0 , arr.length/2 ) )"#;
+    assert!(matches!(validate(code), ValidationResult::Incomplete));
+  }
+
+  #[test]
+  fn validate_regex_looking_code() {
+    let code = r#"/testing/;"#;
+    assert!(matches!(validate(code), ValidationResult::Valid(_)));
+  }
+}