improvements of load driver file

LINQ/LINQ/Interpreter/Expressions/Keywords/ImportDataDriver.vb

@@ -1,4 +1,6 @@
-Namespace Interpreter.Expressions
+Imports Microsoft.VisualBasic.Language
+
+Namespace Interpreter.Expressions
 
     Public Class ImportDataDriver : Inherits KeywordExpression
 
@@ -15,7 +17,28 @@
         End Sub
 
         Public Overrides Function Exec(context As ExecutableContext) As Object
-            Throw New NotImplementedException()
+            If dllName.FileExists Then
+                Return dllName
+            End If
+
+            Dim fileName As Value(Of String) = ""
+            Dim driver As String = dllName
+
+            If driver.ExtensionSuffix <> "dll" Then
+                driver = $"{driver}.dll"
+            End If
+
+            For Each dir As String In {App.HOME, App.CurrentDirectory}
+                If (fileName = $"{dir}/{driver}").FileExists Then
+                    Return fileName
+                End If
+            Next
+
+            Throw New BadImageFormatException($"driver module '{driver}' not found!")
+        End Function
+
+        Public Overrides Function ToString() As String
+            Return $"load driver: {dllName}"
         End Function
     End Class
 End Namespace

LINQ/LINQ/Interpreter/Query/QueryExpression.vb

@@ -73,7 +73,7 @@ Namespace Interpreter.Query
             Dim registry As Registry = globalEnv.registry
 
             For Each name As ImportDataDriver In attaches
-                Call registry.Register(driver:=name.dllName)
+                Call registry.Register(driverDll:=name.Exec(context))
             Next
         End Sub
 

LINQ/LINQ/Runtime/Registry.vb

@@ -50,9 +50,8 @@ Namespace Runtime
 
         ReadOnly drivers As New Dictionary(Of String, IDriverLoader)
 
-        Public Sub Register(driver As String)
-            Dim dll As String = getDllFile(driver)
-            Dim assembly As Assembly = Assembly.LoadFile(dll)
+        Public Sub Register(driverDll As String)
+            Dim assembly As Assembly = Assembly.LoadFile(driverDll)
 
             For Each type As Type In From m As Type
                                      In assembly.GetTypes
@@ -68,26 +67,6 @@ Namespace Runtime
             Next
         End Sub
 
-        Private Function getDllFile(driver As String) As String
-            If driver.FileExists Then
-                Return driver
-            End If
-
-            Dim fileName As Value(Of String) = ""
-
-            If driver.ExtensionSuffix <> "dll" Then
-                driver = $"{driver}.dll"
-            End If
-
-            For Each dir As String In {App.HOME, App.CurrentDirectory}
-                If (fileName = $"{dir}/{driver}").FileExists Then
-                    Return fileName
-                End If
-            Next
-
-            Throw New BadImageFormatException($"driver module '{driver}' not found!")
-        End Function
-
         Public Function GetTypeCodeName(type As Type) As String
             Select Case type
                 Case GetType(Integer) : Return "i32"