AST mapping

Author: cknitt

compiler/ml/ast_mapper_from0.ml

@@ -310,6 +310,20 @@ module E = struct
         | _ -> true)
       attrs
 
+  let extract_finally_attribute attrs =
+    List.find_map
+      (function
+        | {Location.txt = "res.finally"}, Pt.PPat (_, Some expr) -> Some expr
+        | _ -> None)
+      attrs
+
+  let remove_finally_attribute attrs =
+    List.filter
+      (function
+        | {Location.txt = "res.finally"}, _ -> false
+        | _ -> true)
+      attrs
+
   let map_jsx_children sub (e : expression) : Pt.jsx_children =
     let rec visit (e : expression) : Pt.expression list =
       match e.pexp_desc with
@@ -460,8 +474,9 @@ module E = struct
     | Pexp_match (e, pel) ->
       match_ ~loc ~attrs (sub.expr sub e) (sub.cases sub pel)
     | Pexp_try (e, pel) ->
-      try_ ~loc ~attrs (sub.expr sub e) (sub.cases sub pel)
-        (Some (ident {txt = Longident.Lident "_"; loc}))
+      let finally_expr = extract_finally_attribute attrs in
+      let attrs = remove_finally_attribute attrs in
+      try_ ~loc ~attrs (sub.expr sub e) (sub.cases sub pel) finally_expr
     | Pexp_tuple el -> tuple ~loc ~attrs (List.map (sub.expr sub) el)
     (* <></> *)
     | Pexp_construct ({txt = Longident.Lident "[]" | Longident.Lident "::"}, _)

compiler/ml/ast_mapper_to0.ml

@@ -419,7 +419,16 @@ module E = struct
            args)
     | Pexp_match (e, pel) ->
       match_ ~loc ~attrs (sub.expr sub e) (sub.cases sub pel)
-    | Pexp_try (e, pel, _) ->
+    | Pexp_try (e, pel, finally_expr) ->
+      let attrs =
+        match finally_expr with
+        | Some expr ->
+          let finally_attr =
+            sub.attribute sub (Location.mknoloc "res.finally", Parsetree.PPat (Ast_helper.Pat.any (), Some expr))
+          in
+          finally_attr :: attrs
+        | None -> attrs
+      in
       try_ ~loc ~attrs (sub.expr sub e) (sub.cases sub pel)
     | Pexp_tuple el -> tuple ~loc ~attrs (List.map (sub.expr sub) el)
     | Pexp_construct (lid, arg) ->

tests/syntax_tests/data/ast-mapping/TryExpressions.res

@@ -0,0 +1,45 @@
+// Test for try..catch (existing syntax)
+let tryCatch = try {
+  Console.log("Trying")
+} catch {
+| _ => Console.log("Caught")
+}
+
+// Test for try..finally (new syntax)
+let tryFinally = try {
+  Console.log("Trying")
+} finally {
+  Console.log("Finally")
+}
+
+// Test for try..catch..finally (new syntax)
+let tryCatchFinally = try {
+  Console.log("Trying")
+} catch {
+| _ => Console.log("Caught")
+} finally {
+  Console.log("Finally")
+}
+
+// Test with complex expressions
+let complexTry = try {
+  let x = 1 + 2
+  let y = x * 3
+  Some(y)
+} catch {
+| Not_found => None
+| exn => Console.log("Error: " ++ Js.String.make(exn))
+}
+
+// Test nested try expressions
+let nestedTry = try {
+  try {
+    dangerousOperation()
+  } catch {
+  | InnerError => Console.log("Inner caught")
+  }
+} catch {
+| OuterError => Console.log("Outer caught")
+} finally {
+  Console.log("Outer finally")
+}

tests/syntax_tests/data/ast-mapping/expected/TryExpressions.res.txt

@@ -0,0 +1,45 @@
+// Test for try..catch (existing syntax)
+let tryCatch = try {
+  Console.log("Trying")
+} catch {
+| _ => Console.log("Caught")
+}
+
+// Test for try..finally (new syntax)
+let tryFinally = try {
+  Console.log("Trying")
+} finally {
+  Console.log("Finally")
+}
+
+// Test for try..catch..finally (new syntax)
+let tryCatchFinally = try {
+  Console.log("Trying")
+} catch {
+| _ => Console.log("Caught")
+} finally {
+  Console.log("Finally")
+}
+
+// Test with complex expressions
+let complexTry = try {
+  let x = 1 + 2
+  let y = x * 3
+  Some(y)
+} catch {
+| Not_found => None
+| exn => Console.log("Error: " ++ Js.String.make(exn))
+}
+
+// Test nested try expressions
+let nestedTry = try {
+  try {
+    dangerousOperation()
+  } catch {
+  | InnerError => Console.log("Inner caught")
+  }
+} catch {
+| OuterError => Console.log("Outer caught")
+} finally {
+  Console.log("Outer finally")
+}