fix: EXPOSED-815 Check types for QueryAlias.get() at runtime

[ntkoopman]

Description

Check types for QueryAlias.get() at runtime.

Relying purely on compile time checks causes issues when trying to dynamically select fields. E.g.:

object Tasks : UUIDTable("tasks") {
    val weight = integer("weight").nullable()
}

fun main() {
    val expression = Tasks.weight.sum()
    val alias = expression.alias("task_weight")
    val query = Tasks.select(Tasks.weight, alias).alias("all_weight")
    println(query[Tasks.weight]) // works
    println(query[alias]) // works
    val type = if (Random.nextInt(0..2) == 0) Tasks.weight else alias
    println(query[type]) // doesn't work half of the time
}

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Type of Change

Please mark the relevant options with an "X":

• Bug fix
• New feature
• Documentation update

Updates/remove existing public API methods:

• Is breaking change

Affected databases:

• MariaDB
• Mysql5
• Mysql8
• Oracle
• Postgres
• SqlServer
• H2
• SQLite

Checklist

• Unit tests are in place
• The build is green (including the Detekt check)
• All public methods affected by my PR has up to date API docs
• Documentation for my change is up to date

---

Related Issues

[obabichevjb]

As far as I know Column extends ExpressionWithColumnType, so these 2 checks could be joined

[ntkoopman]

Ah, you are right. I've updated it to also handle Columns that are casted to Expression or ExpressionWithColumnType

[obabichevjb]

It would be nice also to filter it for IExpressionAlias

[obabichevjb]

It looks like there is a problem with PR. The test test union with expression and alias in org.jetbrains.exposed.v1.r2dbc.sql.tests.shared.dml.UnionTests fails with java.lang.IllegalStateException: Column not found in original table. Could you check if it's the result of the changes in the PR?

[ntkoopman]

Fixed by inverting the if. This did make me realise you can't get a literal on an alias, and I'm not sure how it should be fixed (probably not in this PR anyway).

select my_alias.??? from (select 10 from some_table) my_alias

The union also generates

SELECT unionAlias.id, exp1, exp2 FROM (SELECT users.id, 10 exp1, 'aaa' exp2 FROM users WHERE users.id = 'andrey' UNION ALL SELECT users.id, 100, 'bbb' FROM users WHERE users.id = 'andrey') unionAlias

while it should probably reference unionAlias.exp1 and unionAlias.exp2

[obabichevjb]

It would be nice to replace it with (added lowercase()):

assertEquals("all_weight.weight", query[column].toExpressionString().lowercase())
            assertEquals("all_weight.weight", query[column as Expression<Int>].toExpressionString().lowercase())
            assertEquals("all_weight.weight", query[column as ExpressionWithColumnType<Int>].toExpressionString().lowercase())

otherwise it fails on some dialects like H2

[ntkoopman]

Oops, fixed, my apologies

[obabichevjb]

In general PR looks good, the added test fails for some databases but it fixable. I'd merge the PR if you fix the test to make it working for all the dialects.

[obabichevjb]

Thank you for contributing, it would be delivered in the next version (should be 1.0.0-beta-5)