quarkusio/quarkus · error · MojoExecutionException

Unable to collect the target directories

Error message

Unable to collect the target directories

What it means

findTargetDirectories walks the scan directory looking for extension target directories; any IOException during that walk is wrapped in a MojoExecutionException 'Unable to collect the target directories'. This happens before any generation work starts.

Source

Thrown at devtools/config-doc-maven-plugin/src/main/java/io/quarkus/maven/config/doc/GenerateConfigDocMojo.java:311

                    // a directory containing a .git file or directory is the root of a separate checkout
                    // (e.g. a git worktree for another branch kept inside the project directory); its
                    // target/ directories belong to a different build and must not be merged into this one.
                    // this doesn't apply to the scan root itself, which is normally the project's own repo root.
                    if (!dir.equals(scanDirectory) && Files.exists(dir.resolve(".git"))) {
                        return FileVisitResult.SKIP_SUBTREE;
                    }

                    return FileVisitResult.CONTINUE;
                }
            });

            // Make sure we are deterministic
            Collections.sort(targets);

            return targets;
        } catch (IOException e) {
            throw new MojoExecutionException("Unable to collect the target directories", e);
        }
    }

    private static Engine initializeQuteEngine(Formatter formatter, Set<String> duplicatePropertyPaths, Format format,
            String theme) {
        EngineBuilder engineBuilder = Engine.builder()
                .addDefaults()
                .addSectionHelper(new UserTagSectionHelper.Factory("configProperty", "configProperty"))
                .addSectionHelper(new UserTagSectionHelper.Factory("configSection", "configSection"))
                .addSectionHelper(new UserTagSectionHelper.Factory("envVar", "envVar"))
                .addSectionHelper(new UserTagSectionHelper.Factory("durationNote", "durationNote"))
                .addSectionHelper(new UserTagSectionHelper.Factory("memorySizeNote", "memorySizeNote"))
                .addValueResolver(new ReflectionValueResolver())
                .addValueResolver(ValueResolver.builder()
                        .applyToBaseClass(String.class)
                        .applyToName("escapeCellContent")
                        .applyToNoParameters()
                        .resolveSync(ctx -> formatter.escapeCellContent((String) ctx.getBase()))

View on GitHub (pinned to e1c734241f)

Solutions

1. Verify the configured scanDirectory exists and is readable
2. Run the plugin from the repository root of a Quarkus extensions checkout
3. Check directory permissions and remove broken symlinks before retrying

Example fix

// before (dir missing)
mvn quarkus:generate-config-doc -DscanDirectory=./missing-extensions
// after
mvn quarkus:generate-config-doc -DscanDirectory=${project.basedir}/extensions

Path scan = Paths.get(scanDirectory);
if (!Files.isDirectory(scan) || !Files.isReadable(scan)) {
    throw new IllegalStateException("Invalid scanDirectory: " + scan);
}

try {
    mojo.execute();
} catch (MojoExecutionException e) {
    if (e.getMessage().contains("Unable to collect the target directories")) {
        logger.error("Check scanDirectory exists and is readable", e.getCause());
    }
}

When it happens

Trigger: findTargetDirectories (invoked via targetDirectories) cannot traverse scanDirectory — it does not exist, lacks read permission, or an I/O error occurs during Files.walk/DirectoryStream iteration.

Common situations: Running the plugin outside a Quarkus multi-module checkout so the scan directory is missing; CI checkouts with restricted permissions; symlink loops or deleted directories mid-scan.

Related errors

• Unable to create directory: ${directory}
• Could not create directory ${outputDirectory}
• Could not create directory ${outputDirectory}
• Failed to create <classesDir>
• Failed to create the output dir ${projectFile}

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/f6e2f2a6e6985607. Report an issue: GitHub.