apache/maven · warning · IllegalArgumentException

Repository list contains duplicate entries. Each repository

Error message

Repository list contains duplicate entries. Each repository must be unique based on its ID and URL. Found {} repositories but only {} unique entries.

What it means

Maven evaluates a profile <activation><file><missing>...</missing> condition by running the configured interpolator over the path expression before checking file existence. If interpolation throws InterpolationException (typically a ${...} expression such as ${env.VAR} or a property that cannot be resolved at activation time), FileProfileActivator catches it, logs this warning (stack trace only with -X), falls through to return false, and the profile is silently treated as NOT active.

Source

Thrown at api/maven-api-core/src/main/java/org/apache/maven/api/services/RepositoryAwareRequest.java:106

     *   <li>Ensures no duplicate repositories exist in the list</li>
     *   <li>Ensures no null repository entries exist in the list</li>
     * </ul>
     *
     * <p>Duplicate detection is based on the {@code RemoteRepository#equals(Object)}
     * method, which typically compares repository IDs and URLs.
     *
     * @param repositories the list of repositories to validate, may be {@code null}
     * @return the same list if validation passes, or {@code null} if input was {@code null}
     * @throws IllegalArgumentException if the list contains duplicate repositories
     * @throws IllegalArgumentException if the list contains null repository entries
     */
    default List<RemoteRepository> validate(List<RemoteRepository> repositories) {
        if (repositories == null) {
            return null;
        }
        HashSet<RemoteRepository> set = new HashSet<>(repositories);
        if (repositories.size() != set.size()) {
            throw new IllegalArgumentException(
                    "Repository list contains duplicate entries. Each repository must be unique based on its ID and URL. "
                            + "Found " + repositories.size() + " repositories but only " + set.size()
                            + " unique entries.");
        }
        if (repositories.stream().anyMatch(Objects::isNull)) {
            throw new IllegalArgumentException(
                    "Repository list contains null entries. All repository entries must be non-null RemoteRepository instances.");
        }
        return repositories;
    }
}

View on GitHub (pinned to e4093d4e12)

Solutions

1. Define the referenced property before the build: -Dprop=value on the mvn command line, <properties> in the POM, or a settings.xml profile
2. Run mvn -X once and read the logged InterpolationException stack to identify the exact expression that fails
3. Replace the expression with a literal path relative to the module basedir (for example target/skip-tests.flag), which needs no interpolation
4. If the marker file is not essential, remove the <missing> condition or switch to <exists> with a stable file

Example fix

<!-- before -->
<activation>
  <file>
    <missing>${env.CI_MARKER}/skip-tests.flag</missing>
  </file>
</activation>
<!-- after: literal module-relative path, no interpolation needed -->
<activation>
  <file>
    <missing>target/skip-tests.flag</missing>
  </file>
</activation>

# fail fast if profile <file> activation still contains unresolved expressions
grep -nE '<(missing|exists)>[^<]*\$\{[^}]+\}' pom.xml */pom.xml && {
  echo 'unresolved expression in profile <file> activation; define the property or use a literal path'
  exit 1
}

When it happens

Trigger: A POM declares <activation><file><missing>${some.expression}/marker</missing></file></activation> and the referenced property or environment variable is undefined when Maven evaluates profile activation; every build emits the warning and the profile never activates.

Common situations: CI agents missing an env var referenced in the activation; a typo in the property name inside <missing>; the property being defined only in one developer's settings.xml profile; activation expressions written for a different Maven version whose activation context exposes different keys.

Related errors

• Repository list contains null entries. All repository entrie
• Bad substitution operator in: ${variable}
• Failed to activate profiles for CI-friendly version processi
• groupId can neither be null, empty nor blank
• artifactId can neither be null, empty nor blank

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/29a037c53521dead. Report an issue: GitHub.