Instant type mapper now allows NULL values

[aboisvert]

When doing a .leftJoin() operation, it's often the case that the right hand side will consist of all null values if the join expression does not match a row.

In my case, I was using an java.time.Instant-typed field, and I was getting exceptions such as,

scala.MatchError: null
    at scalasql.dialects.Dialect$InstantType.get(Dialect.scala:156)
    at scalasql.dialects.Dialect$InstantType.get(Dialect.scala:144)
    at scalasql.core.Queryable$ResultSetIterator.get(Queryable.scala:73)
    at scalasql.core.Expr$ExprQueryable.construct(Expr.scala:50)
    at fanstake.model.Teams$.Teams$$superArg$1$$anonfun$3$$anonfun$2(Team.scala:23)
    at scalasql.query.Table$Internal$TableQueryable.construct(Table.scala:97)
    at scalasql.query.Table$Internal$TableQueryable.construct(Table.scala:97)
    at scalasql.core.Queryable$Row$$anon$1.construct(Queryable.scala:147)
    at scalasql.core.Queryable$Row$$anon$1.construct(Queryable.scala:145)
    at scalasql.core.generated.QueryableRow.Tuple2Queryable$$anonfun$2(Generated.scala:11)
    at scalasql.core.Queryable$Row$TupleNQueryable.construct(Queryable.scala:133)
    at scalasql.core.Queryable$Row$TupleNQueryable.construct(Queryable.scala:133)
    at scalasql.core.generated.QueryableRow.Tuple2Queryable$$anonfun$2(Generated.scala:11)
    at scalasql.core.Queryable$Row$TupleNQueryable.construct(Queryable.scala:133)
    at scalasql.core.Queryable$Row$TupleNQueryable.construct(Queryable.scala:133)
    at scalasql.query.SimpleSelect.queryConstruct(SimpleSelect.scala:225)
    at scalasql.query.SimpleSelect.queryConstruct(SimpleSelect.scala:224)
    at scalasql.query.Query$QueryQueryable.construct(Query.scala:76)
    at scalasql.query.Query$QueryQueryable.construct(Query.scala:76)
    at scalasql.core.DbApi$.scalasql$core$DbApi$Impl$$_$stream$$anonfun$1(DbApi.scala:231)
    at scalasql.core.DbApi$Impl$$anon$1.generate$$anonfun$2(DbApi.scala:417)
    at scalasql.core.DbApi$Impl.configureRunCloseStatement(DbApi.scala:504)
    at scalasql.core.DbApi$Impl$$anon$1.generate(DbApi.scala:420)
    at geny.Generator.foreach(Generator.scala:51)
    at geny.Generator.foreach$(Generator.scala:33)
    at scalasql.core.DbApi$Impl$$anon$1.foreach(DbApi.scala:401)
    at geny.Generator.toBuffer(Generator.scala:127)
    at geny.Generator.toBuffer$(Generator.scala:33)
    at scalasql.core.DbApi$Impl$$anon$1.toBuffer(DbApi.scala:401)
    at geny.Generator.toVector(Generator.scala:135)
    at geny.Generator.toVector$(Generator.scala:33)
    at scalasql.core.DbApi$Impl$$anon$1.toVector(DbApi.scala:401)
    at scalasql.core.DbApi$Impl.run(DbApi.scala:218)
    at fanstake.webapp.controllers.AtlasDTO$.unsafeFindAll(AtlasDTO.scala:88)

The short of it is that Dialect.InstantType, which is a TypeMapper[Instant] didn't allow NULL values to go through.

The fix is trivial - just adding a null pass-through for the match expression.

PS: Similar to InstantType, I noticed that some other TypeMappers do not pass NULL values through. If this PR looks like the right approach to solve this, I can submit a different PR that addresses these other issues.

[lihaoyi]

@aboisvert thanks, this looks great

[lihaoyi]

Let me know if you want to submit further PRs, if so I'll wait for those to land before releasing. If not I can cut a release now for this one

[aboisvert]

Great, thanks! I'd prefer releasing now since we need this fix. That will give me more time to address the others.

[lihaoyi]

@aboisvert 0.1.10 should be out