New error message

before

Unable to find a matching variant of project :platform:
  - Variant 'apiElements' capability org.test:platform:1.9:
      - Incompatible attribute:
          - Required org.gradle.category 'library' and found incompatible value 'platform'.
      - Other attributes:
          - Required org.gradle.dependency.bundling 'external' but no value provided.
          - Required org.gradle.jvm.version '8' but no value provided.
          - Required org.gradle.libraryelements 'classes' but no value provided.
          - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
  - Variant 'enforcedApiElements' capability org.test:platform-derived-enforced-platform:1.9:
      - Incompatible attribute:
          - Required org.gradle.category 'library' and found incompatible value 'enforced-platform'.
      - Other attributes:
          - Required org.gradle.dependency.bundling 'external' but no value provided.
          - Required org.gradle.jvm.version '8' but no value provided.
          - Required org.gradle.libraryelements 'classes' but no value provided.
          - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
  - Variant 'enforcedRuntimeElements' capability org.test:platform-derived-enforced-platform:1.9:
      - Incompatible attribute:
          - Required org.gradle.category 'library' and found incompatible value 'enforced-platform'.
      - Other attributes:
          - Required org.gradle.dependency.bundling 'external' but no value provided.
          - Required org.gradle.jvm.version '8' but no value provided.
          - Required org.gradle.libraryelements 'classes' but no value provided.
          - Required org.gradle.usage 'java-api' and found compatible value 'java-runtime'.
  - Variant 'runtimeElements' capability org.test:platform:1.9:
      - Incompatible attribute:
          - Required org.gradle.category 'library' and found incompatible value 'platform'.
      - Other attributes:
          - Required org.gradle.dependency.bundling 'external' but no value provided.
          - Required org.gradle.jvm.version '8' but no value provided.
          - Required org.gradle.libraryelements 'classes' but no value provided.
          - Required org.gradle.usage 'java-api' and found compatible value 'java-runtime'.

new

The consumer was configured to find an API of a library compatible with Java 8, preferably in the form of class files, and its dependencies declared externally but no matching variant of project :platform was found.
  - Variant 'apiElements' capability org.test:platform:1.9:
      - Incompatible attribute:
          - Required a library but found a platform
      - Other attributes:
          - Doesn't say anything about how its dependencies are found (required its dependencies declared externally)
          - Doesn't say anything about its target Java version (required compatibility with Java 8)
          - Doesn't say anything about its elements (required them preferably in the form of class files)
          - Provides an API
  - Variant 'enforcedApiElements' capability org.test:platform-derived-enforced-platform:1.9:
      - Incompatible attribute:
          - Required a library but found an enforced platform
      - Other attributes:
          - Doesn't say anything about how its dependencies are found (required its dependencies declared externally)
          - Doesn't say anything about its target Java version (required compatibility with Java 8)
          - Doesn't say anything about its elements (required them preferably in the form of class files)
          - Provides an API
  - Variant 'enforcedRuntimeElements' capability org.test:platform-derived-enforced-platform:1.9:
      - Incompatible attribute:
          - Required a library but found an enforced platform
      - Other attributes:
          - Doesn't say anything about how its dependencies are found (required its dependencies declared externally)
          - Doesn't say anything about its target Java version (required compatibility with Java 8)
          - Doesn't say anything about its elements (required them preferably in the form of class files)
          - Required an API but found a runtime
  - Variant 'runtimeElements' capability org.test:platform:1.9:
      - Incompatible attribute:
          - Required a library but found a platform
      - Other attributes:
          - Doesn't say anything about how its dependencies are found (required its dependencies declared externally)
          - Doesn't say anything about its target Java version (required compatibility with Java 8)
          - Doesn't say anything about its elements (required them preferably in the form of class files)
          - Required an API but found a runtime

@melix, do you think the common part can be factored out?

For instance:

• Doesn't say anything about how its dependencies are found (required its dependencies declared externally)
• Doesn't say anything about its target Java version (required compatibility with Java 8)
• Doesn't say anything about its elements (required them preferably in the form of class files)

The attributes are common for all the items. Is it worth the repetition?

For instance:

The consumer was configured to find an API of a library compatible with Java 8, preferably in the form of class files, and its dependencies declared externally but no matching variant of project :platform was found.
  - Variant 'apiElements' capability org.test:platform:1.9:
      - Incompatible attribute:
          - Required a library but found a platform
      - Other attributes:
          - Provides an API
  - Variant 'enforcedApiElements' capability org.test:platform-derived-enforced-platform:1.9:
      - Incompatible attribute:
          - Required a library but found an enforced platform
      - Other attributes:
          - Provides an API
  - Variant 'enforcedRuntimeElements' capability org.test:platform-derived-enforced-platform:1.9:
      - Incompatible attribute:
          - Required a library but found an enforced platform
      - Other attributes:
          - Required an API but found a runtime
  - Variant 'runtimeElements' capability org.test:platform:1.9:
      - Incompatible attribute:
          - Required a library but found a platform
      - Other attributes:
          - Required an API but found a runtime

Common attributes for all the variants:
      - Other attributes:
          - Doesn't say anything about how its dependencies are found (required its dependencies declared externally)
          - Doesn't say anything about its target Java version (required compatibility with Java 8)
          - Doesn't say anything about its elements (required them preferably in the form of class files)

It's a good idea, more refactoring for me :)

Required an API but found a runtime

Is it compatible or not? I read it as incompatible, however, it sits in other attributes group for some reason.

By the way, is there color coding in Required a library but found an enforced platform?
For instance:

Required a library but found an enforced platform

Thanks I'm indeed adding the compatibility aspect too. It's hard to be terse and give the right amount of info at the same time. Regarding colors, no, there's no option for the moment (it's an exception string, basically).

Since you can't use colors, maybe backticks or asterisks (pseudo markdown?). Btw, this does look so much friendlier!

I would really like to have colors (e.g. bold vs regular).
It makes a huge difference.