Issue#4 Adding .singleOption

scalasql/core/src/DbApi.scala

@@ -219,7 +219,26 @@ object DbApi {
         }
       }
     }
-
+
+    def runOption[Q, R](query: Q, fetchSize: Int = -1, queryTimeoutSeconds: Int = -1)(
+        implicit qr: Queryable[Q, Option[R]],
+        fileName: sourcecode.FileName,
+        lineNum: sourcecode.Line
+    ): Option[R] = {
+      assert(qr.isSingleRowOption(query))
+      val res = stream(query, fetchSize, queryTimeoutSeconds)(
+        qr.asInstanceOf[Queryable[Q, Seq[?]]],
+        fileName,
+        lineNum
+      )
+      val results = res.take(2).toVector
+      if (results.size == 0) None
+      else if (results.size == 1) Some(results.head.asInstanceOf[R])
+      else {
+        throw new AssertionError(s"Single row query must return 1 result, not ${results.size}")
+      }
+    }
+
     def stream[Q, R](query: Q, fetchSize: Int = -1, queryTimeoutSeconds: Int = -1)(
         implicit qr: Queryable[Q, Seq[R]],
         fileName: sourcecode.FileName,

scalasql/core/src/Queryable.scala

@@ -48,6 +48,15 @@ trait Queryable[-Q, R] {
    */
   def isSingleRow(q: Q): Boolean
 
+  /**
+   * Whether this query expects a single row to be returned, if so we can assert on
+   * the number of rows and raise an error if 2+ rows are present. Returns
+   * None if 0 rows are present.
+   * @param q
+   * @return
+   */
+  def isSingleRowOption(q: Q): Boolean
+
   /**
    * Converts the given queryable value into a [[SqlStr]], that can then be executed
    * by the underlying SQL JDBC interface
@@ -91,6 +100,7 @@ object Queryable {
     def isGetGeneratedKeys(q: Q): Option[Queryable.Row[?, ?]] = None
     def isExecuteUpdate(q: Q): Boolean = false
     def isSingleRow(q: Q): Boolean = true
+    def isSingleRowOption(q: Q): Boolean = true
     def walkLabels(): Seq[List[String]]
     def walkLabels(q: Q): Seq[List[String]] = walkLabels()
 

scalasql/query/src/GetGeneratedKeys.scala

@@ -9,6 +9,7 @@ import scalasql.core.{Context, Expr, Queryable, SqlStr, WithSqlExpr}
  */
 trait GetGeneratedKeys[Q, R] extends Query[Seq[R]] {
   def single: Query.Single[R] = new Query.Single(this)
+  def singleOption: Query.SingleOption[R] = new Query.SingleOption(this)
 }
 
 object GetGeneratedKeys {
@@ -24,6 +25,7 @@ object GetGeneratedKeys {
     protected def queryWalkLabels(): Seq[List[String]] = Nil
     protected def queryWalkExprs(): Seq[Expr[?]] = Nil
     protected override def queryIsSingleRow = false
+    protected override def queryIsSingleRowOption = false
     protected override def queryIsExecuteUpdate = true
 
     override private[scalasql] def renderSql(ctx: Context): SqlStr = Renderable.renderSql(base)(ctx)

scalasql/query/src/Query.scala

@@ -11,6 +11,7 @@ trait Query[R] extends Renderable {
   protected def queryWalkLabels(): Seq[List[String]]
   protected def queryWalkExprs(): Seq[Expr[?]]
   protected def queryIsSingleRow: Boolean
+  protected def queryIsSingleRowOption: Boolean
   protected def queryGetGeneratedKeys: Option[Queryable.Row[?, ?]] = None
   protected def queryIsExecuteUpdate: Boolean = false
 
@@ -26,6 +27,7 @@ object Query {
     protected def queryWalkLabels(): Seq[List[String]] = Nil
     protected def queryWalkExprs(): Seq[Expr[?]] = Nil
     protected override def queryIsSingleRow = true
+    protected override def queryIsSingleRowOption = true
     protected override def queryIsExecuteUpdate = true
   }
 
@@ -38,6 +40,7 @@ object Query {
     protected def queryWalkLabels() = query.queryWalkLabels()
     protected def queryWalkExprs() = query.queryWalkExprs()
     protected override def queryIsSingleRow = query.queryIsSingleRow
+    protected override def queryIsSingleRowOption = query.queryIsSingleRowOption
     protected override def queryIsExecuteUpdate = query.queryIsExecuteUpdate
   }
 
@@ -49,6 +52,7 @@ object Query {
     protected def queryWalkLabels() = qr.walkLabels(expr)
     protected def queryWalkExprs() = qr.walkExprs(expr)
     protected override def queryIsSingleRow = qr.isSingleRow(expr)
+    protected override def queryIsSingleRowOption = qr.isSingleRowOption(expr)
     protected override def queryIsExecuteUpdate = qr.isExecuteUpdate(expr)
   }
 
@@ -57,6 +61,7 @@ object Query {
   def walkLabels[R](q: Query[R]) = q.queryWalkLabels()
   def walkSqlExprs[R](q: Query[R]) = q.queryWalkExprs()
   def isSingleRow[R](q: Query[R]) = q.queryIsSingleRow
+  def isSingleRowOption[R](q: Query[R]) = q.queryIsSingleRowOption
   def construct[R](q: Query[R], args: Queryable.ResultSetIterator) = q.queryConstruct(args)
 
   /**
@@ -70,6 +75,7 @@ object Query {
     override def walkLabels(q: Q) = q.queryWalkLabels()
     override def walkExprs(q: Q) = q.queryWalkExprs()
     override def isSingleRow(q: Q) = q.queryIsSingleRow
+    override def isSingleRowOption(q: Q) = q.queryIsSingleRowOption
 
     def renderSql(q: Q, ctx: Context): SqlStr = q.renderSql(ctx)
 
@@ -86,4 +92,17 @@ object Query {
     protected override def queryConstruct(args: Queryable.ResultSetIterator): R =
       query.queryConstruct(args).asInstanceOf[R]
   }
+
+  /**
+   * A [[Query]] that wraps another [[Query]] but sets [[queryIsSingleRow]] to `true`
+   */
+  class SingleOption[R](protected val query: Query[Seq[R]]) extends Query.DelegateQuery[R]
+  {
+    protected override def queryIsSingleRowOption: Boolean = true
+
+    private[scalasql] def renderSql(ctx: Context): SqlStr = Renderable.renderSql(query)(ctx)
+
+    protected override def queryConstruct(args: Queryable.ResultSetIterator): R =
+      query.queryConstruct(args).asInstanceOf[R]
+  }
 }