@@ -28,6 +28,7 @@
 - A little performance improvement for JSX V4 runtime helper by removing one object allocation for components with key prop. https://.com/rescript-lang/rescript-compiler/pull/6376
 - The error message for "toplevel expressions should evaluate to unit" has been revamped and improved. https://.com/rescript-lang/rescript-compiler/pull/6407
 - Improve "Somewhere wanted" error messages by changing wording and adding more context + suggested solutions to the error messages where appropriate. https://.com/rescript-lang/rescript-compiler/pull/6410
+- Add smart printer for pipe-chains. https://.com/rescript-lang/rescript-compiler/pull/6411
 
 # 11.0.0-rc.3
 

@@ -11,8 +11,7 @@ let rec addAnnotationsToTypes_ ~config ~(expr : Typedtree.expression)
 let aName =
 if aName = "*opt*" then
 match arg_label with
-| Optional l ->
-l
+| Optional l -> l
 | _ -> "" (* should not happen *)
 else aName
 in
@@ -56,6 +55,7 @@ and addAnnotationsToFields ~config (expr : Typedtree.expression)
 in
 ({field with nameJS = name} :: nextFields1, types1)
 | _ -> (fields, argTypes)
+[@@live]
 
 (** Recover from expr the renaming annotations on named arguments. *)
 let addAnnotationsToFunctionType ~config (expr : Typedtree.expression)

@@ -3527,8 +3527,8 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 Doc.concat
 [spacingBeforeOperator; Doc.text operatorTxt; spacingAfterOperator]
 in
-let printOperand ~isLhs expr parentOperator =
-let rec flatten ~isLhs expr parentOperator =
+let printOperand ~isLhs ~isMultiline expr parentOperator =
+let rec flatten ~isLhs ~isMultiline expr parentOperator =
 if ParsetreeViewer.isBinaryExpression expr then
 match expr with
 | {
@@ -3541,7 +3541,7 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 ParsetreeViewer.flattenableOperators parentOperator operator
 && not (ParsetreeViewer.hasAttributes expr.pexp_attributes)
 then
-let leftPrinted = flatten ~isLhs:true left operator in
+let leftPrinted = flatten ~isLhs:true ~isMultiline left operator in
 let rightPrinted =
 let rightPrinteableAttrs, rightInternalAttrs =
 ParsetreeViewer.partitionPrintableAttributes
@@ -3585,12 +3585,26 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 Doc.rparen;
 ]
 else
-Doc.concat
-[
-leftPrinted;
-printBinaryOperator ~inlineRhs:false operator;
-rightPrinted;
-]
+match operator with
+| ("|." | "|.u") when isMultiline ->
+(* If the pipe-chain is written over multiple lines, break automatically
+* `let x = a->b->c -> same line, break when line-width exceeded
+* `let x = a->
+* b->c` -> pipe-chain is written on multiple lines, break the group *)
+Doc.breakableGroup ~forceBreak:true
+(Doc.concat
+[
+leftPrinted;
+printBinaryOperator ~inlineRhs:false operator;
+rightPrinted;
+])
+| _ ->
+Doc.concat
+[
+leftPrinted;
+printBinaryOperator ~inlineRhs:false operator;
+rightPrinted;
+]
 in
 
 let doc =
@@ -3665,7 +3679,7 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 | Braced braces -> printBraces doc expr braces
 | Nothing -> doc)
 in
-flatten ~isLhs expr parentOperator
+flatten ~isLhs ~isMultiline expr parentOperator
 in
 match expr.pexp_desc with
 | Pexp_apply
@@ -3679,8 +3693,8 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 || ParsetreeViewer.isBinaryExpression rhs
 || printAttributes ~state expr.pexp_attributes cmtTbl <> Doc.nil) ->
 let lhsHasCommentBelow = hasCommentBelow cmtTbl lhs.pexp_loc in
-let lhsDoc = printOperand ~isLhs:true lhs op in
-let rhsDoc = printOperand ~isLhs:false rhs op in
+let lhsDoc = printOperand ~isLhs:true ~isMultiline:false lhs op in
+let rhsDoc = printOperand ~isLhs:false ~isMultiline:false rhs op in
 Doc.group
 (Doc.concat
 [
@@ -3697,12 +3711,16 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 | Pexp_apply
 ( {pexp_desc = Pexp_ident {txt = Longident.Lident operator}},
 [(Nolabel, lhs); (Nolabel, rhs)] ) ->
+let isMultiline =
+lhs.pexp_loc.loc_start.pos_lnum < rhs.pexp_loc.loc_start.pos_lnum
+in
+
 let right =
 let operatorWithRhs =
 let rhsDoc =
 printOperand
 ~isLhs:(ParsetreeViewer.isRhsBinaryOperator operator)
-rhs operator
+~isMultiline rhs operator
 in
 Doc.concat
 [
@@ -3722,7 +3740,7 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
 [
 printOperand
 ~isLhs:(not @@ ParsetreeViewer.isRhsBinaryOperator operator)
-lhs operator;
+~isMultiline lhs operator;
 right;
 ])
 in

@@ -215,13 +215,16 @@ let f = () => {
 </div>
 }
 
-myPromise->Js.Promise.then_(value => {
+myPromise
+->Js.Promise.then_(value => {
 Js.log(value)
 Js.Promise.resolve(value + 2)
-}, _)->Js.Promise.then_(value => {
+}, _)
+->Js.Promise.then_(value => {
 Js.log(value)
 Js.Promise.resolve(value + 3)
-}, _)->Js.Promise.catch(err => {
+}, _)
+->Js.Promise.catch(err => {
 Js.log2("Failure!!", err)
 Js.Promise.resolve(-2)
 }, _)

@@ -0,0 +1,33 @@
+let myFunc = (strA, strB) => strA ++ strB
+
+"expr1"->myFunc("expr2")->myFunc("expr3")
+
+"expr1"
+->myFunc("expr2")
+->myFunc("expr3")
+
+"expr1"
+->myFunc("expr2")
+->myFunc("expr3")
+
+"expr1"
+->myFunc("expr2")
+->myFunc("expr3")
+->myFunc("expr4")
+
+myPromise->Promise.then(v => {
+Js.log(v)
+Promise.resolve(v)
+})
+
+myPromise->Promise.then(v => {
+Js.log(v)
+Promise.resolve(v)
+})
+
+let messages = React.useMemo(() =>
+messagesById
+->StringMap.valuesToArray
+->Array.filter(ChatMessage.isVisibleInSimpleFilter)
+->Array.toSorted(ChatMessage.compareByDateAsc)
+, [messagesById])

@@ -0,0 +1,31 @@
+let myFunc = (strA, strB) => strA ++ strB
+
+"expr1"->myFunc("expr2")->myFunc("expr3")
+
+"expr1"
+->myFunc("expr2")->myFunc("expr3")
+
+"expr1"->myFunc("expr2")
+->myFunc("expr3")
+
+"expr1"->myFunc("expr2")
+->myFunc("expr3")->myFunc("expr4")
+
+myPromise->Promise.then(v => {
+Js.log(v)
+Promise.resolve(v)
+})
+
+myPromise
+->Promise.then(v => {
+Js.log(v)
+Promise.resolve(v)
+})
+
+let messages = React.useMemo(() =>
+messagesById
+->StringMap.valuesToArray
+->Array.filter(ChatMessage.isVisibleInSimpleFilter)
+->Array.toSorted(ChatMessage.compareByDateAsc)
+, [messagesById])
+