quarkusio/quarkus · error · IOException

You can't create a project when the directory is not empty:

Error message

You can't create a project when the directory is not empty: + targetDirectory

What it means

CodestartProcessor.checkTargetDir validates the target directory before generating project files. This error means the given path exists, is a directory, but already contains files, so generating a project would risk overwriting existing content. The library refuses to proceed to protect the existing directory contents.

Source

Thrown at independent-projects/tools/codestarts/src/main/java/io/quarkus/devtools/codestarts/core/CodestartProcessor.java:75

                    .filter(l::dirExists)
                    .forEach(languageDir -> processLanguageDir(projectResource, l, languageDir, finalData));
        });
    }

    public void checkTargetDir() throws IOException {
        if (!Files.exists(targetDirectory)) {
            boolean mkdirStatus = targetDirectory.toFile().mkdirs();
            if (!mkdirStatus) {
                throw new IOException("Failed to create the project directory: " + targetDirectory);
            }
            return;
        }
        if (!Files.isDirectory(targetDirectory)) {
            throw new IOException("Project path needs to point to a directory: " + targetDirectory);
        }
        final String[] files = targetDirectory.toFile().list();
        if (files != null && files.length > 0) {
            throw new IOException("You can't create a project when the directory is not empty: " + targetDirectory);
        }
    }

    public void writeFiles() throws IOException {
        for (Map.Entry<String, List<TargetFile>> e : files.entrySet()) {
            final String relativePath = e.getKey();
            final CodestartFileStrategyHandler strategy = getStrategy(relativePath).orElse(getSelectedDefaultStrategy());
            log.debug("processing file '%s' with strategy %s", relativePath, strategy.name());
            strategy.process(targetDirectory, relativePath, e.getValue(), data);
        }
    }

    public static List<CodestartFileStrategy> buildStrategies(Map<String, String> spec) {
        final List<CodestartFileStrategy> codestartFileStrategyHandlers = new ArrayList<>(spec.size());

        for (Map.Entry<String, String> entry : spec.entrySet()) {
            final CodestartFileStrategyHandler handler = CodestartFileStrategyHandler.BY_NAME.get(entry.getValue());
            if (handler == null) {

View on GitHub (pinned to e1c734241f)

Solutions

1. Empty the target directory (remove or move its contents) and re-run generation
2. Choose a different, empty or non-existent target directory
3. Pre-check the directory yourself with Files.list and abort or warn the user before calling generate

Example fix

// before
generate.generateProject(targetDir);
// after
try (Stream<Path> s = Files.list(targetDir)) {
    if (s.findAny().isPresent()) {
        throw new IllegalStateException("Target dir must be empty: " + targetDir);
    }
}
generate.generateProject(targetDir);

try (Stream<Path> s = Files.list(targetDir)) {
    if (s.findAny().isPresent()) throw new IllegalStateException("Target dir not empty: " + targetDir);
} else if (!Files.isDirectory(targetDir)) {
    throw new IllegalStateException("Target path is not a directory: " + targetDir);
}

try {
    generate.generateProject(targetDir);
} catch (IOException e) {
    if (e.getMessage() != null && e.getMessage().startsWith("You can't create a project when the directory is not empty")) {
        // clean up or choose a different directory, then retry
    } else throw e;
}

When it happens

Trigger: Calling generateProject (via CodestartProjectGeneration/CodestartLoader APIs or quarkus CLI create) into an existing, non-empty directory.

Common situations: Running project generation twice into the same folder; generating into a folder that already contains a git repo, README, or IDE files; accidentally pointing targetDir at the parent project directory.

Related errors

• Could not create directory ${outputDirectory}
• Failed to create the project directory: + targetDirectory
• Project path needs to point to a directory: + targetDirector
• Could not create directory ${dir}
• Failed to create output directory for generated sources: %s

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/e07625879cd7e9aa. Report an issue: GitHub.