Liquibase diff without indexes fails when diffChangeLog declared - indexing

Question

i'm new to liquibase and i was playing around with the diff command. It works perfectly fine but recently found this and i can't figure out why it's not functioning in this specific context.
so the main problem is that i want to compare two databases but without indexes. these are dynamically generated on primary keys and get different names, but are in fact equivalent. liquibase does not understand so i want to run diff without indexes.
so i add this to my pom.xml:
<diffTypes>tables, views, columns, primaryKeys, foreignKeys, uniqueconstraints</diffTypes>
it runs as expected, liquibase does not compare indexes.
in the next step, i want to generate the diff as changelog, so i add a diffChangeLog-File
<diffTypes>tables, views, columns, primaryKeys, foreignKeys, uniqueconstraints</diffTypes>
<diffChangeLogFile>src/main/diffs/diff_test.xml</diffChangeLogFile>
when running liquibase:diff, it fails:
[ERROR] Failed to execute goal org.liquibase:liquibase-maven-plugin:3.4.1:diff (default-cli) on project liquibase_artifactID: Error setting up or running Liquibase: liquibase.command.CommandExecutionException: liquibase.exception.UnexpectedLiquibaseException: Could not resolve MissingObjectChangeGenerator dependencies due to dependency cycle. Dependencies:
[ERROR] [] -> Catalog -> []
[ERROR] [] -> Schema -> []
[ERROR] [Index] -> ForeignKey -> []
[ERROR] [] -> UniqueConstraint -> []
[ERROR] [] -> Column -> []
[ERROR] [] -> Table -> []
[ERROR] [] -> PrimaryKey -> []
[ERROR] [] -> View -> []
[ERROR] -> [Help 1]
Why does liquibase act like this? Is it "illegal" to generate a diffChangeLog without indexes?
When including indexes to diffTypes it works, but the generated Changelog is unusable because liquibase wants to change the indexes with createIndex and dropIndex. But these statements are not executable (it fails to drop an index on primary keys and it can't create an index when it already exists).
Any ideas how to generate a usable changelog without indexes? Or did i just miss something?

Answer 1

The answer to the question is there in the exception message:
Could not resolve MissingObjectChangeGenerator dependencies due to dependency cycle.
It then lists the dependencies.
Internally, Liquibase is generating a directed graph of dependencies and making sure that the dependencies are all satisfied. If you would like to see the code that does this, see the class DiffToChangeLog and its internal private class DependencyGraph