Properties migrator causes an application to fail to start if it tries to map a property whose metadata data entry contains an invalid configuration property name

[larsgrefer]

TL;DR: The spring-boot-configuration-processor should check for (or fix) invalid configuration property names found in META-INF/additional-spring-configuration-metadata.json at compile time.

We currently have the following situation:

1. There is an invalid property name in META-INF/additional-spring-configuration-metadata.json of an external library.
2. When the library is compiled, spring-boot-configuration-processor copies the invalid property name over to META-INF/spring-configuration-metadata.json.
3. Our application depends on both the library and spring-boot-properties-migrator
4. Our application fails to start with a org.springframework.boot.context.properties.source.InvalidConfigurationPropertyNameException.

Since the library is an external dependency out of our control, our only option is to exclude spring-boot-properties-migrator in our application until the metadata is fixed by the author of the external library.

This problem could have been prevented, if the invalid name were already caught in Step 2.
I therefore propose that spring-boot-configuration-processor should check META-INF/additional-spring-configuration-metadata.json for invalid property names, before copying them over to META-INF/spring-configuration-metadata.json. It can then either fail the compilation or convert the properties to their correct form.

[wilkinsona]

Thanks for the suggestion. Unfortunately, I cannot reproduce the behavior that you have described.

I have some json describing the properties that looks like this:

{
  "groups": [
    {
      "name": "some",
      "type": "com.example.demo.SomeProperties",
      "sourceType": "com.example.demo.SomeProperties"
    }
  ],
  "properties": [
    {
      "name": "broken¢∞§¢#¢∞broken",
      "type": "java.lang.Boolean"
    },
    {
      "name": "some.two",
      "type": "java.lang.String",
      "sourceType": "com.example.demo.SomeProperties"
    },
    {
      "name": "some.one",
      "type": "java.lang.String",
      "sourceType": "com.example.demo.SomeProperties",
      "deprecated": true,
      "deprecation": {
        "replacement": "some.two"
      }
    }
  ],
  "hints": []
}

And some configuration that sets the deprecated property:

some.one=alpha

The app then starts successfully, warning me about the deprecated property and its mapping:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.7.5)

2022-11-17 17:47:22.196  INFO 72755 --- [           main] com.example.demo.Gh32729Application      : Starting Gh32729Application using Java 17.0.5 on wilkinsona-a01.vmware.com with PID 72755 (/Users/awilkinson/dev/workspaces/spring-projects/spring-boot/main/gh-32729/build/classes/java/main started by awilkinson in /Users/awilkinson/dev/workspaces/spring-projects/spring-boot/main/gh-32729)
2022-11-17 17:47:22.197  INFO 72755 --- [           main] com.example.demo.Gh32729Application      : No active profile set, falling back to 1 default profile: "default"
2022-11-17 17:47:22.523  INFO 72755 --- [           main] com.example.demo.Gh32729Application      : Started Gh32729Application in 0.537 seconds (JVM running for 0.751)
2022-11-17 17:47:22.526  WARN 72755 --- [           main] o.s.b.c.p.m.PropertiesMigrationListener  : 
The use of configuration keys that have been renamed was found in the environment:

Property source 'Config resource 'class path resource [application.properties]' via location 'optional:classpath:/'':
        Key: some.one
                Line: 1
                Replacement: some.two


Each configuration key has been temporarily mapped to its replacement for your convenience. To silence this warning, please update your configuration to use the new keys.

Can you please provide a minimal example that shows the property with invalid characters causing a failure?

[larsgrefer]

Thanks for looking into this.

Running ./gradlew app:bootRun on https://github.com/larsgrefer/spring-boot-32729 should reproduce the issue.

[wilkinsona]

Thanks, @larsgrefer. I've reproduced the problem now.

[wilkinsona]

I don't think we can address this by failing compile time as it may result in compilation failures for things that are currently harmless. Without the properties migrator on the classpath, everything works nice with the IDE reporting that old.serverSSLPort has been deprecated and that new.server-ssl-port is its replacement. It's also possible to retrieve old.serverSSLPort from the environment using old.serverSSLPort or old.server-ssl-port. We could perhaps issue a warning at compile time that old.serverSSLPort isn't in the canonical form. I think we should also look at updating the properties migrator so that it doesn't cause a failure.

[wilkinsona]

Possible change to the properties migrator that I'd like to discuss with @snicoll.

[larsgrefer]

Allowing the properties migrator to work with non-canonical property keys would be Ideal.

This way it's easier to provide migration metadata for older (before spring boot) properties.

[snicoll]

That change looks good @wilkinsona, thanks!