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kotlinlang

In 2.4.0-Beta1, I noticed that multiple diagnostics reported at the same location with the same name but different messages (for example - multiple different issues) now only print the first one (though both are hit in the debugger). Is this intentional behavior and plugins should merge the messages their-side or is this a bug I should report?

Yes, it is expected.
In 2.4.0 we <https://github.com/JetBrains/kotlin/commit/94d1947f8695e78742fb83f1e2ad90dca935d038|started> using <https://github.com/JetBrains/kotlin/blob/77f32f134fe34b3cfe2e0d422af6c0bb0d1a6d0e/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/impl/DeduplicatingDiagnosticReporter.kt#L12|DeduplicatingDiagnosticReporter> not only for frontend, but for backends too. So two diagnostics on the same source element with the same diagnostic factory are considered duplicated everywhere.

gotcha. Do you have thoughts on deduping by message too? Metro uses a pattern in a few places of reporting errors from anywhere and then exiting processing if any were reported during analysis

It's not that easy. The message does not exists until it was explicitly asked to generate.
Did you consider using different diagnostic factories for different errors?

Generally yes, but sometimes it's multiple instances of the same diagnostic but different messages. For example, multiple missing bindings from a graph where the only location we have to report is the graph itself