Escaped character in nested placeholder not detected properly and leads to invalid parts

[semeiskii]

Problem
After upgrade from Spring Boot 3.3 to Spring Boot 3.4 a property which uses custom loader and contains placeholder inside it is not resolved properly.

application.yaml:

spring:
  config:
    import: sm-stub://

app:
  environment: qa
  a-service-url: ${sm-stub\://projects/my-project/secrets/${app.environment}_a-service_url/versions/latest}

In the application:

@Value("${app.a-service-url}")
private String aServiceUrl;

The resolved value is "//projects/my-project/secrets/qa_a-service_url/versions/latest" [NOK]
Expected value is the one returned by the custom property source for the "projects/my-project/secrets/qa_a-service_url/versions/latest" location.

Minimal reproducible example
https://github.com/semeiskii/spring-boot-property-resolving-bug

[bclozel]

It looks like a duplicate of #34124. Please check the discussion there for best practices.
Also, this should be "fixed" in Spring Framework 6.2.2 already so you can verify that your application works with that version right now.

[snicoll]

Thanks for the report and the sample.

As pointed out in the related issue, : is a reserved character that you shouldn't be using. That double indirection that you use makes ${sm-stub://projects/my-project/secrets/${app.environment}_a-service_url/versions/latest} very artificial.

If you insist on it, you can escape the separator. However, you need to double backslash it for the backslah to be taken into account, i.e.:

app.a-service-url:${sm-stub\\://projects/my-project/secrets/${app.environment}_a-service_url/versions/latest}

Unfortunately, this makes me discover another regression in the parser so I'll use this issue to fix it.