apache/iceberg · error · GradleException

Found unsupported Scala version:

Error message

Found unsupported Scala version: 

What it means

settings.gradle validates the Scala version (from -DscalaVersion or defaultScalaVersion) against knownScalaVersions. Since the build supports only specific Scala minor versions per Spark release, an unknown value throws this GradleException naming the unsupported Scala version.

Solutions

1. Use one of the known Scala versions, typically -DscalaVersion=2.12 or 2.13 (check knownScalaVersions in gradle.properties).
2. Omit -DscalaVersion to use defaultScalaVersion.
3. Ensure the Scala version is compatible with the requested Spark versions (e.g. Spark 3.x with 2.12/2.13).
4. Fix typos in the property value.

Example fix

// before
./gradlew build -DscalaVersion=2.11
// after
./gradlew build -DscalaVersion=2.13

KNOWN=$(grep knownScalaVersions gradle.properties | cut -d= -f2); [[ ",$KNOWN," == *",$SCALA_VERSION,"* ]] || echo "Unsupported Scala: $SCALA_VERSION"

When it happens

Trigger: Running Gradle with -DscalaVersion=2.11 (or another value not in knownScalaVersions, e.g. only 2.12 and 2.13 are known); setting scalaVersion in gradle.properties to a typo or unsupported minor.

Common situations: Attempting a Scala 2.11 build on a modern Iceberg; typo like '2.14'; copying flags from an older branch where different Scala versions were supported.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Found unsupported Flink versions:
• Found unsupported Kafka versions:
• Found unsupported Spark versions:
• Cannot assume role to sign REST requests because is not…
• Cannot clean files incrementally when snapshot IDs are…

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/e9badd2d6f6e8751. Report an issue: GitHub.

Appendix: source

Thrown at settings.gradle:107

List<String> sparkVersions = sparkVersionsString != null && !sparkVersionsString.isEmpty() ? sparkVersionsString.split(",") : []

if (!knownSparkVersions.containsAll(sparkVersions)) {
  throw new GradleException("Found unsupported Spark versions: " + (sparkVersions - knownSparkVersions))
}

List<String> knownKafkaVersions = System.getProperty("knownKafkaVersions").split(",")
String kafkaVersionsString = System.getProperty("kafkaVersions") != null ? System.getProperty("kafkaVersions") : System.getProperty("defaultKafkaVersions")
List<String> kafkaVersions = kafkaVersionsString != null && !kafkaVersionsString.isEmpty() ? kafkaVersionsString.split(",") : []

if (!knownKafkaVersions.containsAll(kafkaVersions)) {
  throw new GradleException("Found unsupported Kafka versions: " + (kafkaVersions - knownKafkaVersions))
}

List<String> knownScalaVersions = System.getProperty("knownScalaVersions").split(",")
String scalaVersion = System.getProperty("scalaVersion") != null ? System.getProperty("scalaVersion") : System.getProperty("defaultScalaVersion")

if (!knownScalaVersions.contains(scalaVersion)) {
  throw new GradleException("Found unsupported Scala version: " + scalaVersion)
}

if (!flinkVersions.isEmpty()) {
  include 'flink'
  project(':flink').name = 'iceberg-flink'
}

if (flinkVersions.contains("1.20")) {
  include ":iceberg-flink:flink-1.20"
  include ":iceberg-flink:flink-runtime-1.20"
  project(":iceberg-flink:flink-1.20").projectDir = file('flink/v1.20/flink')
  project(":iceberg-flink:flink-1.20").name = "iceberg-flink-1.20"
  project(":iceberg-flink:flink-runtime-1.20").projectDir = file('flink/v1.20/flink-runtime')
  project(":iceberg-flink:flink-runtime-1.20").name = "iceberg-flink-runtime-1.20"
}

if (flinkVersions.contains("2.1")) {
  include ":iceberg-flink:flink-2.1"

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