Github user HyukjinKwon commented on the issue:
https://github.com/apache/spark/pull/18749
For source compatibility, in the commit,
https://github.com/apache/spark/pull/18749/commits/389fc6ef788bf971f846ca36f49cea6a1c98b0d0,
I tried to move back to `extended` to show it passes the tests and keep the
source compatibility.
For binary compatibility, I tested in the way I described before -
https://github.com/databricks/scala-style-guide/issues/46.
With `ExpressionDescription.java` assuming this is Spark 2.2.0:
```java
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
public @interface ExpressionDescription {
String usage() default "";
String extended() default "";
}
```
With `Main.scala` assuming this is the user application compiled with Spark
2.2.0:
```scala
@ExpressionDescription(
usage = "I am usage",
extended = """
I am extended
""")
case class A()
object Main {
def main(args: Array[String]): Unit = {
val df =
scala.reflect.classTag[A].runtimeClass.getAnnotation(classOf[ExpressionDescription]).
println(df.usage())
println(df.extended())
}
}
```
```
javac ExpressionDescription.java
scalac Main.scala
scala Main
```
prints
```
I am usage
I am extended
```
And then, I changed `ExpressionDescription.java` assuming we merged this
change into Spark's next release:
```diff
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
public @interface ExpressionDescription {
String usage() default "";
String extended() default "";
+ String arguments() default "";
+ String examples() default "";
+ String note() default "";
+ String since() default "";
}
```
and then I ran
```
javac ExpressionDescription.java
scala Main
```
this looks working fine as below:
```
I am usage
I am extended
```
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