[Repo Assist] fix: activate empty-string guard in DesignTimeConnectionString.Parse; add parse edge-case tests

src/SqlClient.DesignTime/DesignTimeConnectionString.fs

@@ -12,7 +12,9 @@ type internal DesignTimeConnectionString =
     | NameInConfig of name: string * value: string * provider: string
 
     static member Parse(s: string, resolutionFolder, fileName) =
-        match s.Trim().Split([|'='|], 2, StringSplitOptions.RemoveEmptyEntries) with
+        // Use StringSplitOptions.None so that the empty-string guard actually fires:
+        // RemoveEmptyEntries turns "" into [||] which skips the [|""|] branch.
+        match s.Trim().Split([|'='|], 2, StringSplitOptions.None) with
             | [| "" |] -> invalidArg "ConnectionStringOrName" "Value is empty!"
             | [| prefix; tail |] when prefix.Trim().ToLower() = "name" -> 
                 let name = tail.Trim()

tests/SqlClient.DesignTime.Tests/DesignTimeConnectionStringTests.fs

@@ -28,3 +28,37 @@ let RuntimeConfig() =
     let x = DesignTimeConnectionString.Parse("name=AdventureWorks", __SOURCE_DIRECTORY__, "app.config")
     let actual = Linq.RuntimeHelpers.LeafExpressionConverter.EvaluateQuotation( x.RunTimeValueExpr(isHostedExecution = false)) |> unbox
     Assert.Equal<string>( adventureWorks, actual)
+
+// ---- Edge case tests for Parse ----
+
+[<Fact>]
+let ``Empty string throws ArgumentException`` () =
+    // The [| "" |] guard in Parse must fire — not be skipped by RemoveEmptyEntries.
+    Assert.Throws<System.ArgumentException>(
+        fun () -> DesignTimeConnectionString.Parse("", resolutionFolder = "", fileName = "") |> box
+    ) |> ignore
+
+[<Fact>]
+let ``Whitespace-only string throws ArgumentException`` () =
+    Assert.Throws<System.ArgumentException>(
+        fun () -> DesignTimeConnectionString.Parse("   ", resolutionFolder = "", fileName = "") |> box
+    ) |> ignore
+
+[<Fact>]
+let ``Literal connection string is parsed correctly`` () =
+    let cs = "Data Source=.;Initial Catalog=Test;Integrated Security=True"
+    let x = DesignTimeConnectionString.Parse(cs, resolutionFolder = "", fileName = "")
+    match x with
+    | Literal value -> Assert.Equal<string>(cs, value)
+    | _ -> failwith "Expected Literal"
+
+[<Fact>]
+let ``Literal IsDefinedByLiteral is true`` () =
+    let x = DesignTimeConnectionString.Parse("Server=.;Database=Test", resolutionFolder = "", fileName = "")
+    Assert.True(x.IsDefinedByLiteral)
+
+[<Fact>]
+let ``Literal Value returns the connection string`` () =
+    let cs = "Server=.;Database=Northwind"
+    let x = DesignTimeConnectionString.Parse(cs, resolutionFolder = "", fileName = "")
+    Assert.Equal<string>(cs, x.Value)