From 33dfe680d17b885b7fee364a9a908109d9b5d1df Mon Sep 17 00:00:00 2001
From: Florian Verdonck <florian.verdonck@outlook.com>
Date: Tue, 20 Apr 2021 19:50:55 +0200
Subject: [PATCH] Keep lambda at same line in multiline dotget. Fixes #1662.
 (#1663)

---
 src/Fantomas.Tests/DotGetTests.fs | 82 +++++++++++++++++++++++++++++++
 src/Fantomas/CodePrinter.fs       | 29 +++++++++++
 src/Fantomas/SourceParser.fs      |  6 +++
 3 files changed, 117 insertions(+)

diff --git a/src/Fantomas.Tests/DotGetTests.fs b/src/Fantomas.Tests/DotGetTests.fs
index a75ac7df96..29b79c0008 100644
--- a/src/Fantomas.Tests/DotGetTests.fs
+++ b/src/Fantomas.Tests/DotGetTests.fs
@@ -1125,3 +1125,85 @@ module Foo =
 
         ()
 """
+
+[<Test>]
+let ``single line dotget lambda, followed by application`` () =
+    formatSourceString
+        false
+        """
+Foo(fun x ->  x).Bar().Meh
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+Foo(fun x -> x).Bar().Meh
+"""
+
+[<Test>]
+let ``multiline dotget lambda, followed by application, 1662`` () =
+    formatSourceString
+        false
+        """
+type Class() =
+    member this.``kk``() =
+        async {
+            mock
+                .Setup(fun m ->
+                m.CreateBlah
+                    (It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Id>(), It.IsAny<uint32>()))
+                .Returns(Some mock)
+                .End
+        }
+        |> Async.StartImmediate
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+type Class() =
+    member this.kk() =
+        async {
+            mock
+                .Setup(fun m ->
+                    m.CreateBlah(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Id>(), It.IsAny<uint32>()))
+                .Returns(Some mock)
+                .End
+        }
+        |> Async.StartImmediate
+"""
+
+[<Test>]
+let ``multiline dotget lambda, followed by multiple applications`` () =
+    formatSourceString
+        false
+        """
+mock
+                .Setup(fun m ->
+                // some comment
+                m.CreateBlah
+                    (It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Id>(), It.IsAny<uint32>()))
+                .Returns(Some mock)
+                .OrNot()
+                .End
+"""
+        { config with MaxLineLength = 80 }
+    |> prepend newline
+    |> should
+        equal
+        """
+mock
+    .Setup(fun m ->
+        // some comment
+        m.CreateBlah(
+            It.IsAny<string>(),
+            It.IsAny<string>(),
+            It.IsAny<Id>(),
+            It.IsAny<uint32>()
+        ))
+    .Returns(Some mock)
+    .OrNot()
+    .End
+"""
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index 52e53a04b6..22880ea406 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -1815,6 +1815,35 @@ and genExpr astContext synExpr ctx =
             +> !-(sprintf ".%s" s)
             +> sepSpaceOrIndentAndNlnIfExpressionExceedsPageWidth (col sepSpace es (genExpr astContext))
 
+        // Foo(fun x -> x).Bar().Meh
+        | DotGetAppDotGetAppParenLambda (e, px, appLids, es, lids) ->
+            let short =
+                genExpr astContext e
+                +> genExpr astContext px
+                +> genLidsWithDots appLids
+                +> col sepComma es (genExpr astContext)
+                +> genLidsWithDots lids
+
+            let long =
+                let functionName =
+                    match e with
+                    | LongIdentPieces lids when (List.moreThanOne lids) -> genFunctionNameWithMultilineLids id lids
+                    | TypeApp (LongIdentPieces lids, ts) when (List.moreThanOne lids) ->
+                        genFunctionNameWithMultilineLids (genGenericTypeParameters astContext ts) lids
+                    | _ -> genExpr astContext e
+
+                functionName
+                +> indent
+                +> genExpr astContext px
+                +> sepNln
+                +> genLidsWithDotsAndNewlines appLids
+                +> col sepComma es (genExpr astContext)
+                +> sepNln
+                +> genLidsWithDotsAndNewlines lids
+                +> unindent
+
+            fun ctx -> isShortExpression ctx.Config.MaxDotGetExpressionWidth short long ctx
+
         // Foo().Bar
         | DotGetAppParen (e, px, lids) ->
             let shortAppExpr =
diff --git a/src/Fantomas/SourceParser.fs b/src/Fantomas/SourceParser.fs
index 8be6a72602..769291c755 100644
--- a/src/Fantomas/SourceParser.fs
+++ b/src/Fantomas/SourceParser.fs
@@ -995,6 +995,12 @@ let (|DotGetAppParen|_|) e =
     | DotGet (App (e, [ ConstExpr (SynConst.Unit, _) as px ]), lids) -> Some(e, px, lids)
     | _ -> None
 
+let (|DotGetAppDotGetAppParenLambda|_|) (e: SynExpr) =
+    match e with
+    | DotGet (App (DotGet (App (e, [ Paren (_, SynExpr.Lambda _, _, _) as px ]), appLids), es), lids) ->
+        Some(e, px, appLids, es, lids)
+    | _ -> None
+
 /// Gather series of application for line breaking
 let rec (|DotGetApp|_|) =
     function