From c0e56ec82a259229654bcd0112f108b05c82da17 Mon Sep 17 00:00:00 2001
From: Retheesh Erathu <sumod8898@gmail.com>
Date: Tue, 26 Oct 2021 14:46:38 +0200
Subject: [PATCH] Avoid vanity alignment in long pattern match

Fixes https://github.com/fsprojects/fantomas/issues/1926
---
 src/Fantomas.Tests/PatternMatchingTests.fs | 31 ++++++++++++++++++++++
 src/Fantomas/CodePrinter.fs                | 23 +++++++++++++---
 2 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/src/Fantomas.Tests/PatternMatchingTests.fs b/src/Fantomas.Tests/PatternMatchingTests.fs
index ed05a9f262..f0050737e2 100644
--- a/src/Fantomas.Tests/PatternMatchingTests.fs
+++ b/src/Fantomas.Tests/PatternMatchingTests.fs
@@ -2056,3 +2056,34 @@ match!
 | None -> false
 | Some balance -> someRetrievedBalance = balance
 """
+
+[<Test>]
+let ``vanity alignment used when using long case in match block, 1926`` () =
+    formatSourceString
+        false
+        """
+match foo with
+| SomeVeryLongMatchCase(1234567890, 1234567890, 1234567890, 1234567890, 1234567890, 1234567890, 1234567890, 1234567890, 1234567890, 1234567890) ->
+    bar()
+| _ -> () """
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+match foo with
+| SomeVeryLongMatchCase
+    (
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890,
+        1234567890
+    ) -> bar ()
+| _ -> ()
+"""
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index 79e956f2b7..b9bcc1ae00 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -4971,10 +4971,25 @@ and genPat astContext pat =
                     | _ -> true
                 | _ -> true
 
-        ifElse isParenNecessary sepOpenT sepSpace
-        +> genPat astContext p
-        +> enterNodeTokenByName pat.Range RPAREN
-        +> ifElse isParenNecessary sepCloseT sepNone
+        let shortExpr =
+            ifElse isParenNecessary sepOpenT sepSpace
+            +> genPat astContext p
+            +> enterNodeTokenByName pat.Range RPAREN
+            +> ifElse isParenNecessary sepCloseT sepNone
+
+        let longExpr =
+            ifElse
+                astContext.IsInsideMatchClausePattern
+                (ifElse isParenNecessary ((indent +> sepNln +> sepOpenT +> indent +> sepNln)) sepNone)
+                (ifElse isParenNecessary sepOpenT sepSpace)
+            +> genPat astContext p
+            +> enterNodeTokenByName pat.Range RPAREN
+            +> (ifElse
+                    astContext.IsInsideMatchClausePattern
+                    (ifElse isParenNecessary (unindent +> sepNln +> sepCloseT +> unindent) sepNone)
+                    (ifElse isParenNecessary sepCloseT sepNone))
+
+        expressionFitsOnRestOfLine shortExpr longExpr
     | PatTuple ps ->
         expressionFitsOnRestOfLine
             (col sepComma ps (genPat astContext))