Fix formatter handling of wildcard pattern matching in record (#7224)

Author: shulhi

CHANGELOG.md

@@ -23,6 +23,7 @@
 - Handle absolute file paths in gentype. https://github.com/rescript-lang/rescript-compiler/pull/7111
 - Fix "rescript format" with many files. https://github.com/rescript-lang/rescript-compiler/pull/7081
 - Fix exponential notation syntax. https://github.com/rescript-lang/rescript/pull/7174
+- Fix formatter handling of wildcard in pattern matching records with no fields specified. https://github.com/rescript-lang/rescript/pull/7224
 
 #### :house: Internal
 

jscomp/syntax/src/res_printer.ml

@@ -2377,6 +2377,8 @@ and printPattern ~state (p : Parsetree.pattern) cmtTbl =
       Doc.group (Doc.concat [variantName; argsDoc])
     | Ppat_type ident ->
       Doc.concat [Doc.text "#..."; printIdentPath ident cmtTbl]
+    | Ppat_record ([], Open) ->
+      Doc.concat [Doc.lbrace; Doc.text "_"; Doc.rbrace]
     | Ppat_record (rows, openFlag) ->
       Doc.group
         (Doc.concat

jscomp/syntax/tests/printer/pattern/expected/record.res.txt

@@ -116,3 +116,14 @@ let get_age3 = ({age: module(P: S), name: _}) => age2
 let get_age3 = ({age: exception Exit, name: _}) => age2
 
 let get_age3 = ({age: %raw("__GC"), name: _}) => age2
+
+let get_age3 = ({age, _}) => age
+let get_age3 = ({_}) => ""
+let get_age3 = () =>
+  switch x {
+  | {age, _} => age
+  }
+let get_age3 = () =>
+  switch x {
+  | {_} => ""
+  }

jscomp/syntax/tests/printer/pattern/record.res

@@ -60,3 +60,14 @@ let get_age3 = ({age: module(P: S), name: _}) => age2
 let get_age3 = ({age: exception Exit, name: _}) => age2
 
 let get_age3 = ({age: %raw("__GC"), name: _}) => age2
+
+let get_age3 = ({age, _}) => age
+let get_age3 = ({_}) => ""
+let get_age3 = () => 
+  switch x {
+  | {age, _} => age
+  }
+let get_age3 = () => 
+  switch x {
+  | {_} => ""
+  }