Quarkus Configuration Disambiguation strategy for environment variables fails in 3.17.0+

[ryandens]

Describe the bug

The Quarkus configuration reference guide describes how to disambiguate configuration properties with dynamic segments. The recommended approach is to check in the expected configuration key with a value left empty to enable it to be configured via an environment variable.

Expected behavior

The server can start/tests can run without providing an optional entry for a dynamic configuration value.

Actual behavior

This behavior breaks on an upgrade from 3.16.4 to 3.17.0. I tested 3.18.3 and 3.19.0.CR1 to ensure this hasn't been fixed yet.

It fails with the following error in a Quarkus component test:

Configuration validation failed:
	java.util.NoSuchElementException: SRCFG00040: The config property com.ryandens.deployments."fake-deployment-name-1" is defined as the empty String ("") which the following Converter considered to be null: io.smallrye.config.Converters$BuiltInConverter
io.smallrye.config.ConfigValidationException: Configuration validation failed:
	java.util.NoSuchElementException: SRCFG00040: The config property com.ryandens.deployments."fake-deployment-name-1" is defined as the empty String ("") which the following Converter considered to be null: io.smallrye.config.Converters$BuiltInConverter
	at io.smallrye.config.SmallRyeConfig.buildMappings(SmallRyeConfig.java:139)
	at io.smallrye.config.SmallRyeConfig.<init>(SmallRyeConfig.java:93)
	at io.smallrye.config.SmallRyeConfigBuilder.build(SmallRyeConfigBuilder.java:773)
	at io.quarkus.test.component.QuarkusComponentTestExtension.startContainer(QuarkusComponentTestExtension.java:454)
	at io.quarkus.test.component.QuarkusComponentTestExtension.beforeEach(QuarkusComponentTestExtension.java:237)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	Suppressed: java.lang.NullPointerException: Cannot invoke "java.util.List.iterator()" because "injectedParams" is null
		at io.quarkus.test.component.QuarkusComponentTestExtension.destroyDependentTestMethodParams(QuarkusComponentTestExtension.java:349)
		at io.quarkus.test.component.QuarkusComponentTestExtension.afterEach(QuarkusComponentTestExtension.java:249)
		... 2 more

A similar error occurs with the Quarkus test

java.lang.RuntimeException: Failed to start quarkus
java.lang.RuntimeException: java.lang.RuntimeException: Failed to start quarkus
	at io.quarkus.test.junit.QuarkusTestExtension.throwBootFailureException(QuarkusTestExtension.java:611)
	at io.quarkus.test.junit.QuarkusTestExtension.interceptTestClassConstructor(QuarkusTestExtension.java:695)
	at java.base/java.util.Optional.orElseGet(Optional.java:364)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
Caused by: java.lang.RuntimeException: Failed to start quarkus
	at io.quarkus.runner.ApplicationImpl.doStart(Unknown Source)
	at io.quarkus.runtime.Application.start(Application.java:101)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at io.quarkus.runner.bootstrap.StartupActionImpl.run(StartupActionImpl.java:305)
	at io.quarkus.test.junit.QuarkusTestExtension.doJavaStart(QuarkusTestExtension.java:224)
	at io.quarkus.test.junit.QuarkusTestExtension.ensureStarted(QuarkusTestExtension.java:578)
	at io.quarkus.test.junit.QuarkusTestExtension.beforeAll(QuarkusTestExtension.java:628)
	... 1 more
Caused by: io.smallrye.config.ConfigValidationException: Configuration validation failed:
	java.util.NoSuchElementException: SRCFG00040: The config property com.ryandens.deployments."fake-deployment-name-1" is defined as the empty String ("") which the following Converter considered to be null: io.smallrye.config.Converters$BuiltInConverter
	at io.smallrye.config.SmallRyeConfig.buildMappings(SmallRyeConfig.java:139)
	at io.smallrye.config.SmallRyeConfig.<init>(SmallRyeConfig.java:93)
	at io.smallrye.config.SmallRyeConfigBuilder.build(SmallRyeConfigBuilder.java:773)
	at io.quarkus.runtime.generated.Config.readConfig(Unknown Source)
	at io.quarkus.runtime.generated.Config.createRunTimeConfig(Unknown Source)
	at io.quarkus.deployment.steps.RuntimeConfigSetup.deploy(Unknown Source)
	... 8 more


Failed to start quarkus
java.lang.RuntimeException: Failed to start quarkus
	at io.quarkus.runner.ApplicationImpl.doStart(Unknown Source)
	at io.quarkus.runtime.Application.start(Application.java:101)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at io.quarkus.runner.bootstrap.StartupActionImpl.run(StartupActionImpl.java:305)
	at io.quarkus.test.junit.QuarkusTestExtension.doJavaStart(QuarkusTestExtension.java:224)
	at io.quarkus.test.junit.QuarkusTestExtension.ensureStarted(QuarkusTestExtension.java:578)
	at io.quarkus.test.junit.QuarkusTestExtension.beforeAll(QuarkusTestExtension.java:628)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
Caused by: io.smallrye.config.ConfigValidationException: Configuration validation failed:
	java.util.NoSuchElementException: SRCFG00040: The config property com.ryandens.deployments."fake-deployment-name-1" is defined as the empty String ("") which the following Converter considered to be null: io.smallrye.config.Converters$BuiltInConverter
	at io.smallrye.config.SmallRyeConfig.buildMappings(SmallRyeConfig.java:139)
	at io.smallrye.config.SmallRyeConfig.<init>(SmallRyeConfig.java:93)
	at io.smallrye.config.SmallRyeConfigBuilder.build(SmallRyeConfigBuilder.java:773)
	at io.quarkus.runtime.generated.Config.readConfig(Unknown Source)
	at io.quarkus.runtime.generated.Config.createRunTimeConfig(Unknown Source)
	at io.quarkus.deployment.steps.RuntimeConfigSetup.deploy(Unknown Source)
	... 8 more

How to Reproduce?

1. Clone the reproducer: https://github.com/ryandens/quarkus-config-disambiguation-reproducer
2. Run the build, seeing the error in the test report/build scan for the QuarkusComponentTest
3. Run the build, seeing the error in the test report/build scan for the QuarkusTest
4. Run ./gradlew :lib:quarkusDev, seeing that the app fails to start up and serve the API.

Output of uname -a or ver

Darwin mac

Output of java -version

openjdk version "21.0.6" 2025-01-21 LTS

Mandrel or GraalVM version (if different from Java)

No response

Quarkus version or git rev

3.18.3

Build tool (ie. output of mvnw --version or gradlew --version)

8.12.1

Additional information

No response

[quarkus-bot]

/cc @Karm (native-image), @galderz (native-image), @radcortez (config), @zakkak (native-image)

[ryandens]

I believe this issue was incorrectly labeled with area/native-image - though area/config is, of course, appropriate.

[geoand]

cc @radcortez

[ryandens]

I'm wondering, but am unsure, if this has something to do with the behavior change by an upgrade to SmallRye Config 3.10.0 done in 3.17.0.CR1 (quarkus PR: #42227). I skimmed the release notes, and nothing else jumped out at me. There are some in-depth discussions about empty config values in microprofile/microprofile-config#671 and microprofile/microprofile-config#446

[ryandens]

I believe I found the suspect PR for the behavior change. It is in the smallrye upgrade to 3.10.0: smallrye/smallrye-config#1220

This PR adds a new construct to define a required list of keys for a Map like the one I use. I believe changing the behavior of the previously documented config disambiguation was an unintended consequence.

It seems to be tripping up on a call to ConfigMappingInterface.getDefaultValue() in the ConfigMappingGenerator, whereas previously there was a check for if the value was optional

[radcortez]

I'll have a look.