Fix for issue 48 (Exception thrown in outer join with subquery member)

the problem was that the ordering of the table expression was not strict, so the from expression
would get mixed with a join expression.

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

@@ -441,6 +441,12 @@ trait QueryableExpressionNode extends ExpressionNode with UniqueIdInAliaseRequir
 
   def inhibited_=(b: Boolean) = _inhibited = b
 
+  /**
+   * When the join syntax is used, isMemberOfJoinList is true if this instance is not in the from clause
+   * but a 'join element'. 
+   */
+  def isMemberOfJoinList = joinKind != None
+
   // new join syntax
   var joinKind: Option[(String,String)] = None
 

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

@@ -95,9 +95,10 @@ trait DatabaseAdapter {
       }
     }
     else {
-      val texp = qen.tableExpressions.splitAt(1)
-      val firstJoinExpr = texp._1.head
-      val restOfJoinExpr = texp._2
+      val singleNonJoinTableExpression = qen.tableExpressions.filter(! _.isMemberOfJoinList)
+      assert(singleNonJoinTableExpression.size == 1, "join query must have exactly one FROM argument, got : " + qen.tableExpressions)
+      val firstJoinExpr = singleNonJoinTableExpression.head
+      val restOfJoinExpr = qen.tableExpressions.filter(_.isMemberOfJoinList)
       firstJoinExpr.write(sw)
       sw.write(" ")
       sw.write(firstJoinExpr.alias)

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

@@ -129,17 +129,43 @@ class MusicDbTestRun extends QueryTester {
 
     val r = q.map(q0 => (q0.key._1, q0.measures)).toSet
 
-    println("!:" + r)
-
     assertEquals(
       Set((herbyHancock.id, 1),
           (ponchoSanchez.id,1),
           (mongoSantaMaria.id,1),
           (alainCaron.id, 0),
           (hossamRamzy.id, 0)),
       r, 'testJoinWithCompute)
+
+    passed('testJoinWithCompute)
   }
 
+  def testOuterJoinWithSubQuery = {
+    import testInstance._
+
+    val artistsQ = artists.where(_.firstName <> "zozo")
+
+    val q =
+      join(artistsQ,songs.leftOuter)((a,s)=>
+        select((a,s))
+        on(a.id === s.map(_.authorId))
+      ).toList
+
+
+    val artistIdsWithoutSongs = q.filter(_._2 == None).map(_._1.id).toSet
+
+    assertEquals(
+      Set(alainCaron.id,hossamRamzy.id),
+      artistIdsWithoutSongs, 'testOuterJoinWithSubQuery)
+
+    val artistIdsWithSongs = q.filter(_._2 != None).map(_._1.id).toSet
+
+    assertEquals(
+      Set(herbyHancock.id,ponchoSanchez.id,mongoSantaMaria.id),
+      artistIdsWithSongs, 'testOuterJoinWithSubQuery)
+
+    passed('testOuterJoinWithSubQuery)
+  }  
 
   def selfJoinNested3Level =
     from(
@@ -284,6 +310,8 @@ class MusicDbTestRun extends QueryTester {
   def working = {
     import testInstance._
 
+    testOuterJoinWithSubQuery
+
     testJoinWithCompute
 
     testInTautology