projectlombok/lombok · error

Legal values for ' ' are ' ', or ' '.

Error message

Legal values for '%s' are '%s', or '%s'.

What it means

`unrollBoolean` validates boolean format options in FormatPreferences. Each option accepts only its designated true-string, false-string, or absence (default). Any other value throws IllegalArgumentException naming the option and its two legal values.

Solutions

1. Read the message: set the named option to exactly the quoted true value or the quoted false value
2. Remove the key to get the default value
3. Run `java -jar lombok.jar --format-help` to see legal values per option

Example fix

// before
formatOptions.add("finalParams:yes");
// after
formatOptions.add("finalParams:generate"); // or "skip"

if (v != null && !trueStr.equalsIgnoreCase(v) && !falseStr.equalsIgnoreCase(v))
    throw new IllegalArgumentException(name + " must be " + trueStr + " or " + falseStr);

try { delombok.setFormatPreferences(opts); } catch (IllegalArgumentException e) { /* set option to one of the two legal values quoted in the message */ throw e; }

When it happens

Trigger: Supplying a value for a boolean format key (e.g. `suppressWarnings`, `generated`, `finalParams`) that is neither its trueStr nor falseStr, e.g. `getters.final=true` or `skip:maybe`. Fires inside `setFormatPreferences` for every option registered via unrollBoolean.

Common situations: Using generic 'true'/'false' where the option expects 'generate'/'skip' (or vice versa); typos like 'genrate'; tooling that blindly serializes booleans into format options.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Legal values for 'emptyLines' are 'scan', 'indent', or…
• Run java -jar lombok.jar --format-help for detailed format…
• Minor version must be between 0 and 999
• Lombok supports at most v
• Invalid value

AI-assisted analysis of projectlombok/lombok@6d6a3e9fec (2026-09-07). Data as JSON: /api/errors/d9b6e2743a39a6a1. Report an issue: GitHub.

Appendix: source

Thrown at src/delombok/lombok/delombok/FormatPreferences.java:98

		
		this.indent = indent;
		this.filledEmpties = filledEmpties;
		
		this.generateFinalParams = unrollBoolean(preferences, "finalParams", "generate", "skip", true);
		this.generateConstructorProperties = unrollBoolean(preferences, "constructorProperties", "generate", "skip", true);
		this.generateSuppressWarnings = unrollBoolean(preferences, "suppressWarnings", "generate", "skip", true);
		this.generateGenerated = unrollBoolean(preferences, "generated", "generate", "skip", true);
		this.danceAroundIdeChecks = unrollBoolean(preferences, "danceAroundIdeChecks", "generate", "skip", true);
		this.generateDelombokComment = unrollBoolean(preferences, "generateDelombokComment", "generate", "skip", true);
		this.javaLangAsFqn = unrollBoolean(preferences, "javaLangAsFQN", "generate", "skip", true);
	}
	
	private static boolean unrollBoolean(Map<String, String> preferences, String name, String trueStr, String falseStr, boolean defaultVal) {
		String v_ = preferences.get(name.toLowerCase());
		if (v_ == null) return defaultVal;
		if (trueStr.equalsIgnoreCase(v_)) return true;
		if (falseStr.equalsIgnoreCase(v_)) return false;
		throw new IllegalArgumentException("Legal values for '" + name + "' are '" + trueStr + "', or '" + falseStr + "'.");
	}
	
	public static Map<String, String> getKeysAndDescriptions() {
		return KEYS;
	}
	
	/** If true, empty lines should still be appropriately indented. If false, empty lines should be completely blank. */
	public boolean fillEmpties() {
		return filledEmpties == null ? false : filledEmpties;
	}
	
	public String indent() {
		return indent == null ? "\t" : indent;
	}
	
	public boolean generateSuppressWarnings() {
		return generateSuppressWarnings;
	}

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