Multiline pattern proof of concept.

src/Fantomas.Core.Tests/AlignedMultilineBracketStyleTests.fs

@@ -1009,7 +1009,7 @@ let ``record destructuring in let binding`` () =
               printfn "Last Name: %s" ln
               printfn "Age: %i" age
 """
-        config
+        { config with MaxLineLength = 50 }
     |> prepend newline
     |> should
         equal

src/Fantomas.Core.Tests/CrampedMultilineBracketStyleTests.fs

@@ -1453,7 +1453,7 @@ let internal sepSemi (ctx: Context) =
     | true, true -> str " ; "
     <| ctx
 """
-        config
+        { config with MaxLineLength = 80 }
     |> prepend newline
     |> should
         equal
@@ -1578,7 +1578,7 @@ match entities with
       Type = Elephant } ] -> ()
 | _ -> ()
 """
-        config
+        { config with MaxLineLength = 40 }
     |> prepend newline
     |> should
         equal
@@ -1607,7 +1607,7 @@ match entities with
       Type = Elephant } ] -> ()
 | _ -> ()
 """
-        config
+        { config with MaxLineLength = 40 }
     |> prepend newline
     |> should
         equal
@@ -1636,18 +1636,19 @@ match entities with
        Type = Elephant } |] -> ()
 | _ -> ()
 """
-        config
+        { config with MaxLineLength = 40 }
     |> prepend newline
     |> should
         equal
         """
 match entities with
-| [| { Key = "0031ff53-e59b-49e3-8e0f-53f72a3890d1"
-       Type = Elephant }
-     { Key = "0031ff53-e59b-49e3-8e0f-53f72a3890d2"
-       Type = Elephant }
-     { Key = "0031ff53-e59b-49e3-8e0f-53f72a3890d3"
-       Type = Elephant } |] -> ()
+| [|
+    { Key = "0031ff53-e59b-49e3-8e0f-53f72a3890d1"
+      Type = Elephant }
+    { Key = "0031ff53-e59b-49e3-8e0f-53f72a3890d2"
+      Type = Elephant }
+    { Key = "0031ff53-e59b-49e3-8e0f-53f72a3890d3"
+      Type = Elephant } |] -> ()
 | _ -> ()
 """
 

src/Fantomas.Core.Tests/Fantomas.Core.Tests.fsproj

@@ -128,6 +128,8 @@
     <Compile Include="CursorTests.fs" />
     <Compile Include="MultipleDefineCombinationsTests.fs" />
     <Compile Include="ParenthesesTests.fs" />
+    <Compile Include="MultilinePatterns.fs" />
+    <Compile Include="MultilineNamedExpressions.fs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Fantomas.Core\Fantomas.Core.fsproj" />

src/Fantomas.Core.Tests/LambdaTests.fs

@@ -1108,7 +1108,7 @@ let g =
                revisionNumber = r
                processName = pn } -> p, r, pn)
 """
-        config
+        { config with MaxLineLength = 60 }
     |> prepend newline
     |> should
         equal

src/Fantomas.Core.Tests/MultilineNamedExpressions.fs

@@ -0,0 +1,72 @@
+module Fantomas.Core.Tests.MultilineNamedExpressions
+
+open NUnit.Framework
+open FsUnit
+open Fantomas.Core
+open Fantomas.Core.Tests.TestHelpers
+
+[<Test>]
+let ``single named item expression`` () =
+    formatSourceString
+        false
+        """
+let x =
+    ParsedInput.ImplFile(
+        ParsedImplFileInput(
+            contents =
+                [ SynModuleOrNamespace.SynModuleOrNamespace(
+                      decls =
+                          [ a
+                            //
+                            b ]
+                  ) ]
+        )
+    )
+"""
+        { config with MaxLineLength = 80 }
+    |> prepend newline
+    |> should
+        equal
+        """
+let x =
+    ParsedInput.ImplFile(
+        ParsedImplFileInput(contents = [
+            SynModuleOrNamespace.SynModuleOrNamespace(decls = [
+                a
+                //
+                b
+            ])
+        ])
+    )
+"""
+
+// TODO: there is currently no check whether `(a =` fits on the remainder of the line.
+
+[<Test>]
+let ``multiline long identifier in named argument function call`` () =
+    formatSourceString
+        false
+        """
+XXXXXXXXXXXXXXXX
+    // Some comment
+    .YYYYYYYYYYYYYY
+    .ZZZZZZZZZZZZZZZ(
+    a =
+        try b () with ex -> c 
+)
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+XXXXXXXXXXXXXXXX
+    // Some comment
+    .YYYYYYYYYYYYYY
+    .ZZZZZZZZZZZZZZZ(a =
+        try
+            b ()
+        with ex ->
+            c
+    )
+"""