Format to canonical form before checking for idempotency test

Author: shulhi

compiler/syntax/src/res_parsetree_viewer.ml

@@ -161,8 +161,9 @@ let rewrite_underscore_apply_in_pipe expr =
           (fun arg ->
             match arg with
             | ( lbl,
-                ({pexp_desc = Pexp_ident ({txt = Longident.Lident "__x"} as lid)}
-                 as arg_expr) ) ->
+                ({
+                   pexp_desc = Pexp_ident ({txt = Longident.Lident "__x"} as lid);
+                 } as arg_expr) ) ->
               ( lbl,
                 {
                   arg_expr with

compiler/syntax/src/res_parsetree_viewer.mli

@@ -146,7 +146,8 @@ val is_single_pipe_expr : Parsetree.expression -> bool
 (* (__x) => f(a, __x, c) -----> f(a, _, c)  *)
 val rewrite_underscore_apply : Parsetree.expression -> Parsetree.expression
 
-val rewrite_underscore_apply_in_pipe : Parsetree.expression -> Parsetree.expression
+val rewrite_underscore_apply_in_pipe :
+  Parsetree.expression -> Parsetree.expression
 
 (* (__x) => f(a, __x, c) -----> f(a, _, c)  *)
 val is_underscore_apply_sugar : Parsetree.expression -> bool

scripts/test_syntax.sh

@@ -81,6 +81,7 @@ if [[ $ROUNDTRIP_TEST = 1 ]]; then
     mkdir -p temp/$(dirname $file)
     sexpAst1=temp/$file.sexp
     sexpAst2=temp/$file.2.sexp
+    sexpAst3=temp/$file.3.sexp
     rescript1=temp/$file.res
     rescript2=temp/$file.2.res
 
@@ -89,14 +90,21 @@ if [[ $ROUNDTRIP_TEST = 1 ]]; then
       *.resi ) resIntf=-interface ;;
     esac
 
+    # First pass: original file -> AST1 and text1
     $DUNE_BIN_DIR/res_parser $resIntf -print sexp $file > $sexpAst1
     $DUNE_BIN_DIR/res_parser $resIntf -print res $file > $rescript1
 
+    # Second pass: text1 -> AST2 and text2
     $DUNE_BIN_DIR/res_parser $resIntf -print sexp $rescript1 > $sexpAst2
     $DUNE_BIN_DIR/res_parser $resIntf -print res $rescript1 > $rescript2
 
-    diff --unified $sexpAst1 $sexpAst2
+    # Third pass: text2 -> AST3 (to check idempotency after normalization)
+    $DUNE_BIN_DIR/res_parser $resIntf -print sexp $rescript2 > $sexpAst3
+
+    # Check AST idempotency: AST2 should equal AST3 (allows AST1 != AST2 for canonicalization)
+    diff --unified $sexpAst2 $sexpAst3
     [[ "$?" = 1 ]] && echo 1 > $roundtripTestsResult
+    # Check text idempotency: text1 should equal text2
     diff --unified $rescript1 $rescript2
     [[ "$?" = 1 ]] && echo 1 > $roundtripTestsResult
   } & maybeWait