From 5a33609b348a48a7e2f659dc663cd198e539760b Mon Sep 17 00:00:00 2001
From: nojaf <florian.verdonck@outlook.com>
Date: Tue, 22 Dec 2020 22:11:32 +0100
Subject: [PATCH 1/2] Put multiline when condition on the next line. Fixes
 #1320.

---
 src/Fantomas.Tests/PatternMatchingTests.fs | 33 ++++++++++++++++++++++
 src/Fantomas/CodePrinter.fs                |  6 +++-
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/Fantomas.Tests/PatternMatchingTests.fs b/src/Fantomas.Tests/PatternMatchingTests.fs
index ddcc4e04b6..02ce481631 100644
--- a/src/Fantomas.Tests/PatternMatchingTests.fs
+++ b/src/Fantomas.Tests/PatternMatchingTests.fs
@@ -1060,3 +1060,36 @@ let rec (|DoExprAttributesL|_|) =
     | Attributes _ as x :: ys -> Some([ x ], ys)
     | _ -> None
 """
+
+[<Test>]
+let ``multiline when condition, 1320`` () =
+    formatSourceString
+        false
+        """
+module Foo =
+    module Bar =
+            let buildUsage argInfos =
+                match v.IsMember, v.IsInstanceMember, v.LogicalName, v.DisplayName with
+                // Ordinary functions or values
+                | false, _, _, name when
+                    not (hasAttribute<RequireQualifiedAccessAttribute> v.ApparentEnclosingEntity.Attributes) ->
+                    name + " " + parArgs
+                // Ordinary static members or things (?) that require fully qualified access
+                | _, _, _, name -> name + parArgs
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+module Foo =
+    module Bar =
+        let buildUsage argInfos =
+            match v.IsMember, v.IsInstanceMember, v.LogicalName, v.DisplayName with
+            // Ordinary functions or values
+            | false, _, _, name when
+                not (hasAttribute<RequireQualifiedAccessAttribute> v.ApparentEnclosingEntity.Attributes) ->
+                  name + " " + parArgs
+            // Ordinary static members or things (?) that require fully qualified access
+            | _, _, _, name -> name + parArgs
+"""
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index 07e3fe3fe1..cd5d2987e2 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -4230,7 +4230,11 @@ and genClause astContext hasBar (Clause (p, e, eo)) =
         mkRange "arrowRange" p.Range.End e.Range.Start
 
     let body =
-        optPre (!- " when ") sepNone eo (genExpr astContext)
+        optPre
+            (!- " when")
+            sepNone
+            eo
+            (fun e -> sepSpaceOrIndentAndNlnIfExpressionExceedsPageWidth (genExpr astContext e))
         +> sepArrow
         +> leaveNodeTokenByName arrowRange RARROW
         +> clauseBody e

From d02ab8c181d05052e92f7041f48feed7824d2586 Mon Sep 17 00:00:00 2001
From: nojaf <florian.verdonck@outlook.com>
Date: Tue, 22 Dec 2020 22:35:07 +0100
Subject: [PATCH 2/2] Correct indentation of clause body if when condition is
 multiline.

---
 src/Fantomas.Tests/PatternMatchingTests.fs | 37 +++++++++++++++++++++-
 src/Fantomas/CodePrinter.fs                | 18 +++++------
 2 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/src/Fantomas.Tests/PatternMatchingTests.fs b/src/Fantomas.Tests/PatternMatchingTests.fs
index 02ce481631..2e8c75b0a9 100644
--- a/src/Fantomas.Tests/PatternMatchingTests.fs
+++ b/src/Fantomas.Tests/PatternMatchingTests.fs
@@ -1089,7 +1089,42 @@ module Foo =
             // Ordinary functions or values
             | false, _, _, name when
                 not (hasAttribute<RequireQualifiedAccessAttribute> v.ApparentEnclosingEntity.Attributes) ->
-                  name + " " + parArgs
+                name + " " + parArgs
             // Ordinary static members or things (?) that require fully qualified access
             | _, _, _, name -> name + parArgs
 """
+
+[<Test>]
+let ``maintain indent if when condition is multiline`` () =
+    formatSourceString
+        false
+        """
+    match foo with
+    | headToken :: rest when (isOperatorOrKeyword headToken && List.exists (fun k -> headToken.TokenInfo.TokenName = k) keywordTrivia) ->
+          let range =
+              getRangeBetween "keyword" headToken headToken
+
+          let info =
+              Trivia.Create(Keyword(headToken)) range
+              |> List.prependItem foundTrivia
+
+          getTriviaFromTokensThemSelves allTokens rest info
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+match foo with
+| headToken :: rest when
+    (isOperatorOrKeyword headToken
+     && List.exists (fun k -> headToken.TokenInfo.TokenName = k) keywordTrivia) ->
+    let range =
+        getRangeBetween "keyword" headToken headToken
+
+    let info =
+        Trivia.Create(Keyword(headToken)) range
+        |> List.prependItem foundTrivia
+
+    getTriviaFromTokensThemSelves allTokens rest info
+"""
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index cd5d2987e2..c044e49255 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -4229,21 +4229,21 @@ and genClause astContext hasBar (Clause (p, e, eo)) =
     let arrowRange =
         mkRange "arrowRange" p.Range.End e.Range.Start
 
-    let body =
-        optPre
+    let body = clauseBody e
+
+    let astCtx =
+        { astContext with
+              IsInsideMatchClausePattern = true }
+
+    let pat =
+        genPat astCtx p
+        +> optPre
             (!- " when")
             sepNone
             eo
             (fun e -> sepSpaceOrIndentAndNlnIfExpressionExceedsPageWidth (genExpr astContext e))
         +> sepArrow
         +> leaveNodeTokenByName arrowRange RARROW
-        +> clauseBody e
-
-    let astCtx =
-        { astContext with
-              IsInsideMatchClausePattern = true }
-
-    let pat = genPat astCtx p
 
     genTriviaBeforeClausePipe p.Range
     +> ifElse hasBar (sepBar +> atCurrentColumnWithPrepend pat body) (pat +> body)