projectlombok/lombok · error · BuildException

You can't specify both 'from' attribute and nested…

Error message

You can't specify both 'from' attribute and nested filesets. You need one or the other.

What it means

DelombokTaskImpl.execute rejects mutually exclusive input specifications: `from` (single directory) and nested filesets cannot both be present, because the task would not know whether to scan one directory or the fileset list. Both set at once throws BuildException.

Solutions

Remove the `from` attribute and keep the `<fileset>` elements, or
Remove the `<fileset>` elements and keep `from`
To narrow a `from` directory scan, switch entirely to filesets with include/exclude patterns

Example fix

<!-- before -->
<delombok from="src/main/java" to="out">
  <fileset dir="src/main/java"><include name="**/*.java"/></fileset>
</delombok>
<!-- after -->
<delombok to="out">
  <fileset dir="src/main/java"><include name="**/*.java"/></fileset>
</delombok>

Defensive patterns

Strategy: validation

Validate before calling

if (fromDir != null && (path != null || hasFilesets)) throw new IllegalStateException("use from OR filesets, not both");

Try / catch

catch (BuildException e) { if (e.getMessage().contains("both 'from'")) { /* remove one input spec */ } throw e; }

Prevention

Pick one input style per task and document it in the build
Review diffs that merge ant targets
Use include/exclude patterns in filesets instead of adding from

When it happens

Trigger: An Ant `<delombok from="src" to="out">` that also contains `<fileset>` children; calling `setFrom(...)` and `createFileset()`/`setPath(...)` on the task instance programmatically.

Common situations: Merging two working delombok task definitions into one; adding a fileset to narrow the scan while forgetting to remove `from`.

Related errors

AI-assisted analysis of projectlombok/lombok@6d6a3e9fec (2026-09-07). Data as JSON: /api/errors/2a7753c2dfc1fad6. Report an issue: GitHub.

Appendix: source

Thrown at src/delombok/lombok/delombok/ant/DelombokTaskImpl.java:51

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Location;
import org.apache.tools.ant.types.Path;
import org.apache.tools.ant.types.resources.FileResource;

public class DelombokTaskImpl {
	private File fromDir, toDir;
	private Path classpath;
	private Path sourcepath;
	private Path modulepath;
	private boolean verbose;
	private String encoding;
	private Path path;
	private List<String> formatOptions = new ArrayList<String>();
	
	public void execute(Location location) throws BuildException {
		if (fromDir == null && path == null) throw new BuildException("Either 'from' attribute, or nested <fileset> tags are required.");
		if (fromDir != null && path != null) throw new BuildException("You can't specify both 'from' attribute and nested filesets. You need one or the other.");
		if (toDir == null) throw new BuildException("The to attribute is required.");
		
		Delombok delombok = new Delombok();
		if (verbose) delombok.setVerbose(true);
		try {
			if (encoding != null) delombok.setCharset(encoding);
		} catch (UnsupportedCharsetException e) {
			throw new BuildException("Unknown charset: " + encoding, location);
		}
		
		if (classpath != null) delombok.setClasspath(classpath.toString());
		if (sourcepath != null) delombok.setSourcepath(sourcepath.toString());
		if (modulepath != null) delombok.setModulepath(modulepath.toString());
		
		try {
			delombok.setFormatPreferences(Delombok.formatOptionsToMap(formatOptions));
		} catch (InvalidFormatOptionException e) {
			throw new BuildException(e.getMessage() + " Run java -jar lombok.jar --format-help for detailed format help.");

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