null-coalesce operator

src/Terrabuild.Configuration.Tests/TestFiles/WORKSPACE2

@@ -26,7 +26,8 @@ configuration release {
     }
     list: [ 1
             2+3
-            "tutu" ]
+            "tutu"
+            nothing ?? 42 ]
   }
 }
 

src/Terrabuild.Configuration.Tests/Workspace.fs

@@ -72,7 +72,8 @@ let parseWorkspace2() =
                                                        "titi", Expr.String "tagada" ])
                                 "list", Expr.List [ Expr.Number 1
                                                     Expr.Function (Function.Plus, [ Expr.Number 2; Expr.Number 3 ])
-                                                    Expr.String "tutu" ] ] }
+                                                    Expr.String "tutu"
+                                                    Expr.Function (Function.Coalesce, [ Expr.Nothing; Expr.Number 42 ]) ] ] }
         let envDummy =
             { Variables = Map.empty }
         let envSecret =

src/Terrabuild.Configuration/ProjectParser/Lexer.fsl

@@ -27,7 +27,7 @@ rule token = parse
     | "upper" { UPPER }
     | "lower" { LOWER }
     | "version" { VERSION }
-    | "coalesce" { COALESCE }
+    | "??" { COALESCE }
 
     | "project" { PROJECT }
     | "target" { TARGET }

src/Terrabuild.Configuration/ProjectParser/Parser.fsy

@@ -152,7 +152,7 @@ Expr:
     | LOWER LPAREN Expr RPAREN { Expr.Function (Function.Lower, [$3]) }
     | VERSION LPAREN Expr RPAREN { Expr.Function (Function.Version, [$3]) }
     | Expr DOT_LSQBRACKET ExprIndex RSQBRACKET { Expr.Function (Function.Item, [$1; $3]) }
-    | COALESCE LPAREN ExprListContent RPAREN { Expr.Function (Function.Coalesce, $3) }
+    | Expr COALESCE Expr { Expr.Function (Function.Coalesce, [$1; $3]) }
 
 ExprIndex:
     | Expr { $1 }

src/Terrabuild.Configuration/WorkspaceParser/Lexer.fsl

@@ -27,7 +27,7 @@ rule token = parse
     | "upper" { UPPER }
     | "lower" { LOWER }
     | "version" { VERSION }
-    | "coalesce" { COALESCE }
+    | "??" { COALESCE }
 
     | "workspace" { WORKSPACE }
     | "target" { TARGET }

src/Terrabuild.Configuration/WorkspaceParser/Parser.fsy

@@ -143,7 +143,7 @@ Expr:
     | LOWER LPAREN Expr RPAREN { Expr.Function (Function.Lower, [$3]) }
     | VERSION LPAREN Expr RPAREN { Expr.Function (Function.Version, [$3]) }
     | Expr DOT_LSQBRACKET ExprIndex RSQBRACKET { Expr.Function (Function.Item, [$1; $3]) }
-    | COALESCE LPAREN ExprListContent RPAREN { Expr.Function (Function.Coalesce, $3) }
+    | Expr COALESCE Expr { Expr.Function (Function.Coalesce, [$1; $3]) }
 
 ExprIndex:
     | Expr { $1 }

src/Terrabuild.Expressions.Tests/Eval.fs

@@ -72,7 +72,7 @@ let subNumber() =
 [<Test>]
 let coalesce() =
     let expected = Value.Number 42
-    let varUsed, result = eval evaluationContext (Expr.Function (Function.Coalesce, [Expr.Nothing; Expr.Number 42; Expr.String "toto"]))
+    let varUsed, result = eval evaluationContext (Expr.Function (Function.Coalesce, [Expr.Nothing; Expr.Number 42]))
     varUsed |> should be Empty
     result |> should equal expected