projectlombok/lombok · error · IllegalArgumentException

Invalid type name

Error message

Invalid type name 

What it means

TypeName.valueOf parses a dotted type name used as a lombok configuration value. It returns null for null/blank input and throws IllegalArgumentException when any dot-separated segment fails JavaIdentifiers.isValidJavaIdentifier. This ensures only syntactically valid type names are stored as configuration values.

Solutions

1. Fix the type name so every dot-separated part is a valid Java identifier (letters, digits, $, _, not starting with a digit)
2. Remove empty segments caused by leading, trailing, or consecutive dots
3. Pre-validate segments with a regex such as ^[A-Za-z_$][A-Za-z0-9_$]*$ for each part

Example fix

// before
TypeName.valueOf("com.example.-.Foo")
// after
TypeName.valueOf("com.example.core.Foo")

boolean isValidTypeName(String s) {
    if (s == null || s.trim().isEmpty()) return true;
    for (String p : s.trim().split("\\."))
        if (!p.matches("[A-Za-z_$][A-Za-z0-9_$]*")) return false;
    return true;
}

try { TypeName t = TypeName.valueOf(cfg); ... } catch (IllegalArgumentException e) { log.configError("Invalid type name in config", e); }

When it happens

Trigger: Calling TypeName.valueOf with a string where at least one segment between dots is not a valid Java identifier: empty segments (leading/trailing/double dots), segments starting with a digit (e.g. "3rdParty.Type"), or segments containing hyphens, spaces or other symbols.

Common situations: A lombok.config value like 'import: lombok/Getter', a typo'd class name such as 'com.example..Foo', or version-qualified names with hyphens passed where a Java type name is expected.

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

• Minor version must be between 0 and 999
• Lombok supports at most v
• Invalid value
• Invalid identifier
• The declaration must follow the pattern: [LoggerType…

AI-assisted analysis of projectlombok/lombok@6d6a3e9fec (2026-09-07). Data as JSON: /api/errors/8320ab9245ea0ad9. Report an issue: GitHub.

Appendix: source

Thrown at src/core/lombok/core/configuration/TypeName.java:38

 * THE SOFTWARE.
 */
package lombok.core.configuration;

import lombok.core.JavaIdentifiers;

public final class TypeName implements ConfigurationValueType {
	private final String name;
	
	private TypeName(String name) {
		this.name = name;
	}
	
	public static TypeName valueOf(String name) {
		if (name == null || name.trim().isEmpty()) return null;
		
		String trimmedName = name.trim();
		for (String identifier : trimmedName.split("\\.")) {
			if (!JavaIdentifiers.isValidJavaIdentifier(identifier)) throw new IllegalArgumentException("Invalid type name " + trimmedName + " (part " + identifier + ")");
		}
		return new TypeName(trimmedName);
	}
	
	public static String description() {
		return "type-name";
	}
	
	public static String exampleValue() {
		return "<fully.qualified.Type>";
	}
	
	@Override public boolean equals(Object obj) {
		if (!(obj instanceof TypeName)) return false;
		return name.equals(((TypeName) obj).name);
	}
	
	@Override public int hashCode() {

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