optional chaining

todesking · Apr 14, 2024 · d650cd9 · d650cd9
1 parent 14eeaa7
commit d650cd9
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Showing 5 changed files with 28 additions and 2 deletions.
diff --git a/src/ast.rs b/src/ast.rs
@@ -97,6 +97,8 @@ pub enum Expr {
     Paren { expr: Box<Expr> },
     #[serde(rename = "expr_prop")]
     Prop { expr: Box<Expr>, name: Ident },
+    #[serde(rename = "expr_prop_opt")]
+    PropOpt { expr: Box<Expr>, name: Ident },
     #[serde(rename = "expr_index")]
     Index { expr: Box<Expr>, index: Box<Expr> },
     #[serde(rename = "expr_binop")]

diff --git a/src/evaluator.rs b/src/evaluator.rs
@@ -266,6 +266,14 @@ impl Env {
                 let value = self.eval_expr(expr, local_env)?;
                 self.get_prop(&value, name)
             }
+            Expr::PropOpt { expr, name } => {
+                let value = self.eval_expr(expr, local_env)?;
+                if value.is_null() {
+                    Ok(Value::null())
+                } else {
+                    self.get_prop(&value, name)
+                }
+            }
             Expr::Index { expr, index } => {
                 let value = self.eval_expr(expr, local_env)?;
                 let index = self.eval_expr(index, local_env)?;

diff --git a/src/lib.rs b/src/lib.rs
@@ -279,6 +279,12 @@ mod test {
         assert_eval_ok!("{foo: 123, bar: {baz: 999}}.bar.baz", 999);
     }
 
+    #[test]
+    fn optional_chain() {
+        assert_eval_ok!("null?.foo", Value::null());
+        assert_eval_ok!("{foo: 1}?.foo", 1);
+    }
+
     #[test]
     fn array() {
         assert_eval_ok!("[]", array_value![]);

diff --git a/src/value.rs b/src/value.rs
@@ -51,13 +51,13 @@ impl Value {
 
     pub fn use_array<T, F: FnOnce(&[Value]) -> EvalResult<T>>(&self, f: F) -> EvalResult<T> {
         match self {
-            Value::Atom(_) => Err(EvalError::TypeError("Array".into(), self.clone())),
+            Value::Atom(_) => Err(EvalError::type_error("Array", self.clone())),
             Value::Ref(ref_value) => match &**ref_value {
                 RefValue::Array(arr) => {
                     let arr = arr.borrow();
                     f(&arr)
                 }
-                _ => Err(EvalError::TypeError("Array".into(), self.clone())),
+                _ => Err(EvalError::type_error("Array", self.clone())),
             },
         }
     }
@@ -94,6 +94,10 @@ impl Value {
             _ => Err(EvalError::type_error("Object", self.clone())),
         }
     }
+
+    pub fn is_null(&self) -> bool {
+        matches!(self, Value::Atom(AtomValue::Null))
+    }
 }
 
 impl Display for Value {

diff --git a/tree-sitter-borlang/rules.js b/tree-sitter-borlang/rules.js
@@ -39,6 +39,7 @@ const common_rules = {
     $.expr_fun,
     $.expr_if,
     $.expr_prop,
+    $.expr_prop_opt,
     $.expr_index,
   ),
   expr_int: _ => /[0-9]+/,
@@ -143,6 +144,11 @@ const common_rules = {
     '.',
     field('name', $.ident),
   )),
+  expr_prop_opt: $ => prec(Prec.prop, seq(
+    field('expr', $._expr),
+    '?.',
+    field('name', $.ident),
+  )),
   expr_index: $ => prec.left(Prec.index, seq(
     field('expr', $._expr),
     '[',