Yml endpoint error

Config server build from initiazer using spring-boot-starter-parent:2.0.4.RELEASE.

Having these files packed into an app and run with native profile.

$ cat src/main/resources/config/foo.properties 
foo: from foo props
democonfigclient.message: hello spring io

$ cat src/main/resources/config/foo-db.properties 
foo.db: mycooldb

$ cat src/main/resources/config/foo-development.properties 
bar: spam
foo: from foo development

$ cat src/main/resources/config/foo-development-db.properties 
combined: true

Using properties endpoint works but yml errors out:

$ curl localhost:8888/foo-db.properties
democonfigclient.message: hello spring io
foo: from foo props
foo.db: mycooldb

$ curl localhost:8888/foo-db.yml
{"timestamp":"2018-08-20T07:01:13.249+0000","status":500,"error":"Internal Server Error","message":"java.lang.String cannot be cast to java.util.Map","path":"/foo-db.yml"}

With error on a server side.

2018-08-20 10:01:13.247 ERROR 19223 --- [nio-8888-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.ClassCastException: java.lang.String cannot be cast to java.util.Map] with root cause

java.lang.ClassCastException: java.lang.String cannot be cast to java.util.Map
	at org.springframework.cloud.config.server.environment.EnvironmentController$PropertyNavigator.setMapValue(EnvironmentController.java:367) ~[spring-cloud-config-server-2.0.1.RELEASE.jar!/:2.0.1.RELEASE]
	at org.springframework.cloud.config.server.environment.EnvironmentController$PropertyNavigator.access$100(EnvironmentController.java:349) ~[spring-cloud-config-server-2.0.1.RELEASE.jar!/:2.0.1.RELEASE]
	at org.springframework.cloud.config.server.environment.EnvironmentController.convertToMap(EnvironmentController.java:240) ~[spring-cloud-config-server-2.0.1.RELEASE.jar!/:2.0.1.RELEASE]
	at org.springframework.cloud.config.server.environment.EnvironmentController.labelledYaml(EnvironmentController.java:204) ~[spring-cloud-config-server-2.0.1.RELEASE.jar!/:2.0.1.RELEASE]
	at org.springframework.cloud.config.server.environment.EnvironmentController.yaml(EnvironmentController.java:193) ~[spring-cloud-config-server-2.0.1.RELEASE.jar!/:2.0.1.RELEASE]

Maybe we should handle these cases with yml where we have foo and foo.db in props.

Start at EnvironmentController.yaml and its convertToMap/setMapValue methods, identified by the stack trace, and reproduce the failure with the foo-db.yml endpoint using the shown property files. The work is done when YAML output handles overlapping foo and foo.db properties without a ClassCastException and retains the expected values.