fix handling default value

Author: mununki

jscomp/test/alias_default_value_test.js

@@ -2,10 +2,10 @@
 
 
 function Alias_default_value_test$C0(props) {
-  var b = props.b;
-  var b$1 = b !== undefined ? b : 2;
   var a = props.a;
   var a$1 = a !== undefined ? a : 2;
+  var b = props.b;
+  var b$1 = b !== undefined ? b : (a$1 << 1);
   return a$1 + b$1 | 0;
 }
 

res_syntax/src/reactjs_jsx_v4.ml

@@ -1064,9 +1064,15 @@ let transformStructureItem ~config mapper item =
                    (Exp.ident {txt = Lident "props"; loc = Location.none})
                    (Location.mknoloc @@ Lident label))
           in
-          let vbMatchList =
-            if hasDefaultValue namedArgList then List.map vbMatch namedArgList
-            else []
+          let vbMatchExpr namedArgList expr =
+            let rec aux namedArgList =
+              match namedArgList with
+              | [] -> expr
+              | [namedArg] -> Exp.let_ Nonrecursive [vbMatch namedArg] expr
+              | namedArg :: rest ->
+                Exp.let_ Nonrecursive [vbMatch namedArg] (aux rest)
+            in
+            aux (List.rev namedArgList)
           in
           (* type props = { ... } *)
           let propsRecordType =
@@ -1186,8 +1192,9 @@ let transformStructureItem ~config mapper item =
           in
           (* add pattern matching for optional prop value *)
           let expression =
-            if List.length vbMatchList = 0 then expression
-            else Exp.let_ Nonrecursive vbMatchList expression
+            if hasDefaultValue namedArgList then
+              vbMatchExpr namedArgList expression
+            else expression
           in
           (* (ref) => expr *)
           let expression =

res_syntax/tests/ppx/react/expected/aliasProps.res.txt

@@ -5,11 +5,11 @@ module C0 = {
 
   @react.component
   let make = (props: props<'priority, 'text>) => {
+    let _ = props.priority
     let text = switch props.text {
     | Some(text) => text
     | None => "Test"
     }
-    and _ = props.priority
 
     React.string(text)
   }
@@ -25,11 +25,11 @@ module C1 = {
 
   @react.component
   let make = (props: props<'priority, 'text>) => {
+    let p = props.priority
     let text = switch props.text {
     | Some(text) => text
     | None => "Test"
     }
-    and p = props.priority
 
     React.string(p ++ text)
   }

res_syntax/tests/ppx/react/expected/defaultValueProp.res.txt

@@ -4,14 +4,14 @@ module C0 = {
 
   @react.component
   let make = (props: props<'a, 'b>) => {
+    let a = switch props.a {
+    | Some(a) => a
+    | None => 2
+    }
     let b = switch props.b {
     | Some(b) => b
     | None => a * 2
     }
-    and a = switch props.a {
-    | Some(a) => a
-    | None => 2
-    }
 
     React.int(a + b)
   }
@@ -27,11 +27,11 @@ module C1 = {
 
   @react.component
   let make = (props: props<'a, 'b>) => {
-    let b = props.b
-    and a = switch props.a {
+    let a = switch props.a {
     | Some(a) => a
     | None => 2
     }
+    let b = props.b
 
     React.int(a + b)
   }