tracing-enabled: metrics-only fails to start

[Scree]

Hi,
i was trying to get a GraphQL API running and connect it to prometheus. I want to collect metrics on field level, but not expose the tracing data to the request. Luckily there seems to be a property for that: tracing-enabled: metrics-only
But when i set it, the program will crash on start with:

2020-04-14 13:56:57.741 ERROR 101694 --- [           main] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalStateException: Error processing condition on graphql.kickstart.spring.web.boot.GraphQLInstrumentationAutoConfiguration.tracingInstrumentation
	at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:60) ~[spring-boot-autoconfigure-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:108) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForBeanMethod(ConfigurationClassBeanDefinitionReader.java:184) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForConfigurationClass(ConfigurationClassBeanDefinitionReader.java:144) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitions(ConfigurationClassBeanDefinitionReader.java:120) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:331) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:236) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:275) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:95) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:706) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at com.scree.gw2api.Application.main(Application.java:16) ~[classes/:na]
Caused by: org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'metrics' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public or not valid?
	at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:164) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.boot.autoconfigure.condition.OnExpressionCondition.evaluateExpression(OnExpressionCondition.java:60) ~[spring-boot-autoconfigure-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.autoconfigure.condition.OnExpressionCondition.getMatchOutcome(OnExpressionCondition.java:48) ~[spring-boot-autoconfigure-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47) ~[spring-boot-autoconfigure-2.2.6.RELEASE.jar:2.2.6.RELEASE]
	... 17 common frames omitted
Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'metrics' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public or not valid?
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:217) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:104) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:91) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.OpMinus.getValueInternal(OpMinus.java:98) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:188) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.OpOr.getBooleanValue(OpOr.java:56) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.OpOr.getValueInternal(OpOr.java:47) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.OpOr.getValueInternal(OpOr.java:37) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:112) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:272) ~[spring-expression-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:161) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
	... 20 common frames omitted

I think the problem comes from GraphQLInstrumentationAutoConfiguration with

@ConditionalOnExpression("${graphql.servlet.tracing-enabled:'false'}.equals('metrics-only')"
      + "|| ${graphql.servlet.tracing-enabled:'false'}.equals(true)")

${graphql.servlet.tracing-enabled:'false'} will evaluate to true, false or metrics-only. The first two work fine, but for the last one, spring tries to find a matching property instead of interpretating it as a string. With additional quotes around the placeholder it should work.
@ConditionalOnExpression("'${graphql.servlet.tracing-enabled:'false'}'.equals('metrics-only')" + "|| '${graphql.servlet.tracing-enabled:'false'}'.equals(true)")
But i'm not sure if that will impact on the true/false cases as they will compare a string to a boolean then.

As a workaround i'm currently using a double quoted proerty:
tracing-enabled: "'metrics-only'"

[oliemansm]

Thanks for reporting and providing the workaround 👍