Fix for issue 16 : SQL 'in' operator now accepts empty lists and inhi…

…bits

"not in (empty)" tautology and returns an always false for "in (empty)"

  http://github.com/max-l/Squeryl/issues#issue/16

src/main/scala/org/squeryl/dsl/FieldTypes.scala

@@ -101,8 +101,8 @@ trait NumericalExpression[A] extends TypedExpressionNode[A] {
   def in[B <% NumericalExpression[_]](e: Query[B]) = new BinaryOperatorNodeLogicalBoolean(this, e.ast, "in")
   def notIn[B <% NumericalExpression[_]](e: Query[B]) = new BinaryOperatorNodeLogicalBoolean(this, e.ast, "not in")
 
-  def in(l: ListNumerical) = new BinaryOperatorNodeLogicalBoolean(this, l, "in")
-  def notIn(l: ListNumerical) = new BinaryOperatorNodeLogicalBoolean(this, l, "not in")
+  def in(l: ListNumerical) = new InListExpression(this, l, true)
+  def notIn(l: ListNumerical) = new InListExpression(this, l, false)
 
   def between[B,C](b: NumericalExpression[B], c: NumericalExpression[C]) = new BetweenExpression(this, b, c)
 
@@ -147,8 +147,8 @@ trait EnumExpression[A] extends NonNumericalExpression[A] {
 trait StringExpression[A] extends NonNumericalExpression[A] {
   outer =>
 
-  def in(e: ListString) = new BinaryOperatorNodeLogicalBoolean(this, e, "in")
-  def notIn(e: ListString) = new BinaryOperatorNodeLogicalBoolean(this, e, "not in")
+  def in(e: ListString) = new InListExpression(this, e, true)
+  def notIn(e: ListString) = new InListExpression(this, e, false)
 
   //def between(lower: BaseScalarString, upper: BaseScalarString): LogicalBoolean = error("implement me") //new BinaryOperatorNode(this, lower, div) with LogicalBoolean
   def like(e: StringExpression[_])  = new BinaryOperatorNodeLogicalBoolean(this, e, "like")
@@ -164,8 +164,8 @@ trait StringExpression[A] extends NonNumericalExpression[A] {
 
 trait DateExpression[A] extends NonNumericalExpression[A] {
 
-  def in(e: ListDate) = new BinaryOperatorNodeLogicalBoolean(this, e, "in")
-  def notIn(e: ListDate) = new BinaryOperatorNodeLogicalBoolean(this, e, "not in")
+  def in(e: ListDate) = new InListExpression(this, e, true)
+  def notIn(e: ListDate) = new InListExpression(this, e, false)
 
   def ~ = this
 }

src/main/scala/org/squeryl/dsl/ast/ExpressionNode.scala

@@ -86,7 +86,10 @@ trait ExpressionNode {
 
 
 trait ListExpressionNode extends ExpressionNode {
+
   def quotesElement = false
+
+  def isEmpty: Boolean
 }
 
 trait ListNumerical extends ListExpressionNode
@@ -105,6 +108,22 @@ trait ListString extends ListExpressionNode {
 
 class EqualityExpression(override val left: TypedExpressionNode[_], override val right: TypedExpressionNode[_]) extends BinaryOperatorNodeLogicalBoolean(left, right, "=")
 
+class InListExpression(left: ExpressionNode, right: ListExpressionNode, inclusion: Boolean) extends BinaryOperatorNodeLogicalBoolean(left, right, if(inclusion) "in" else "not in") {
+
+  override def inhibited =
+    if(right.isEmpty)
+      (! inclusion)
+    else
+      super.inhibited
+
+  override def doWrite(sw: StatementWriter) =
+    if(inclusion  && right.isEmpty)
+      sw.write("(1 = 0)")
+    else
+      super.doWrite(sw)
+}
+
+
 class BinaryOperatorNodeLogicalBoolean(left: ExpressionNode, right: ExpressionNode, op: String)
   extends BinaryOperatorNode(left,right, op) with LogicalBoolean {
 
@@ -324,7 +343,10 @@ class ConstantExpressionNode[T](val value: T) extends ExpressionNode {
 }
 
 class ConstantExpressionNodeList[T](val value: Traversable[T]) extends ExpressionNode with ListExpressionNode {
-
+
+  def isEmpty =
+    value == Nil
+
   def doWrite(sw: StatementWriter) =
     if(quotesElement)
       sw.write(this.value.map(e=>"'" +e+"'").mkString("(",",",")"))

src/main/scala/org/squeryl/dsl/ast/QueryExpressionElements.scala

@@ -43,6 +43,11 @@ trait QueryExpressionElements extends ExpressionNode {
 
   def whereClause: Option[ExpressionNode]
 
+  def hasUnInhibitedWhereClause =
+    whereClause != None &&
+    (! whereClause.get.inhibited) &&
+    (whereClause.get.children.filter(c => !c.inhibited) != Nil)
+
   def havingClause: Option[ExpressionNode]
 
   def groupByClause: Iterable[ExpressionNode]

src/main/scala/org/squeryl/internals/DatabaseAdapter.scala

@@ -111,7 +111,7 @@ trait DatabaseAdapter {
       }
     }
 
-    if(qen.whereClause != None && qen.whereClause.get.children.filter(c => !c.inhibited) != Nil) {      
+    if(qen.hasUnInhibitedWhereClause) {      
       sw.write("Where")
       sw.nextLine
       sw.writeIndented {

src/test/scala/org/squeryl/tests/musicdb/MusicDb.scala

@@ -260,6 +260,10 @@ class MusicDbTestRun extends QueryTester {
   def working = {
     import testInstance._
 
+    testInTautology
+
+    testNotInTautology
+
     testDynamicWhereClause1
 
     testEnums
@@ -762,6 +766,25 @@ class MusicDbTestRun extends QueryTester {
         select(a)
       )
 
+  def testInTautology = {
+
+    val q = artists.where(_.firstName in Nil).toList
+
+    assertEquals(Nil, q, 'testInTautology)
+
+    passed('testInTautology)
+  }
+
+  def testNotInTautology = {
+
+   val allArtists = artists.map(_.id).toSet
+
+   val q = artists.where(_.firstName notIn Nil).map(_.id).toSet
+
+    assertEquals(allArtists, q, 'testNotInTautology)
+
+    passed('testNotInTautology)
+  }  
 
 //  //class EnumE[A <: Enumeration#Value](val a: A) {
 //  class EnumE[A](val a: A) {