Add newline if there is trivia after the bar in a union case. Fixes #2182. (#2199)

Author: nojaf

CHANGELOG.md

@@ -4,6 +4,9 @@
 
 ### Fixed
 * Multiline parentheses objectExpression in indexer expression. [#2176](https://github.com/fsprojects/fantomas/issues/2176)
+* Blank line over SynEnumCase is restored incorrectly. [#2155](https://github.com/fsprojects/fantomas/issues/2155)
+* XML Doc comments on DU cases seem to get shuffled. [#2188](https://github.com/fsprojects/fantomas/issues/2188)
+* Comment after bar is lost in single case DU. [#2182](https://github.com/fsprojects/fantomas/issues/2182)
 
 ## [4.7.6] - 2022-04-04
 

src/Fantomas.Tests/UnionTests.fs

@@ -996,3 +996,30 @@ type Meh =
     /// When the editor lost focus.
     | Few of DateTime
 """
+
+[<Test>]
+let ``comment after bar of single case DU, 2182`` () =
+    formatSourceString
+        false
+        """
+type LongIdentWithDots =
+    | //[<Experimental("This construct is subject to change in future versions of FSharp.Compiler.Service and should only be used if no adequate alternative is available.")>]
+      LongIdentWithDots of
+       leadingId: LongIdent *
+       operatorName: OperatorName option *
+       trailingId: LongIdent *
+       dotRanges: range list
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+type LongIdentWithDots =
+    | //[<Experimental("This construct is subject to change in future versions of FSharp.Compiler.Service and should only be used if no adequate alternative is available.")>]
+      LongIdentWithDots of
+        leadingId: LongIdent *
+        operatorName: OperatorName option *
+        trailingId: LongIdent *
+        dotRanges: range list
+"""

src/Fantomas/CodePrinter.fs

@@ -4212,20 +4212,23 @@ and genUnionCase
     (hasVerticalBar: bool)
     (UnionCase (ats, px, barRange, _, s, identRange, UnionCaseType fs, range))
     =
-    let shortExpr =
-        colPre wordOf sepStar fs (genField { astContext with IsUnionField = true } "")
+    let shortExpr = col sepStar fs (genField { astContext with IsUnionField = true } "")
 
     let longExpr =
-        wordOf
-        +> indent
+        indent
         +> sepNln
         +> atCurrentColumn (col (sepStar +> sepNln) fs (genField { astContext with IsUnionField = true } ""))
         +> unindent
 
     genPreXmlDoc px
-    +> ifElse hasVerticalBar (genTriviaForOptionOr SynUnionCase_Bar barRange sepBar) sepNone
-    +> genOnelinerAttributes astContext ats
-    +> genTriviaFor Ident_ identRange !-s
+    +> genTriviaForOptionOr SynUnionCase_Bar barRange (ifElse hasVerticalBar sepBar sepNone)
+    +> atCurrentColumn (
+        // If the bar has a comment after, add a newline and print the identifier on the same column on the next line.
+        sepNlnWhenWriteBeforeNewlineNotEmpty sepNone
+        +> genOnelinerAttributes astContext ats
+        +> genTriviaFor Ident_ identRange !-s
+        +> onlyIf (List.isNotEmpty fs) wordOf
+    )
     +> onlyIf (List.isNotEmpty fs) (expressionFitsOnRestOfLine shortExpr longExpr)
     |> genTriviaFor SynUnionCase_ range