ANTLR installation corrupted; cannot find ANTLR messages for

Error message

ANTLR installation corrupted; cannot find ANTLR messages format file  + fileName

What it means

Emitted by the ANTLR tool's ErrorManager when the classloader cannot locate the StringTemplate messages group file (org/antlr/v4/tool/templates/messages/format/antlr.stg) that defines all tool message formats. The tool then calls panic(), aborting, because without the format file it cannot render any diagnostics. This almost always means the antlr jar/classpath is broken or incomplete.

Source

Thrown at tool/src/org/antlr/v4/tool/ErrorManager.java:232

    /** The format gets reset either from the Tool if the user supplied a command line option to that effect
     *  Otherwise we just use the default "antlr".
     */
    public void setFormat(String formatName) {
		STGroupFile loadedFormat;

		synchronized (loadedFormats) {
			loadedFormat = loadedFormats.get(formatName);
			if (loadedFormat == null) {
				String fileName = FORMATS_DIR + formatName + STGroup.GROUP_FILE_EXTENSION;
				ClassLoader cl = Thread.currentThread().getContextClassLoader();
				URL url = cl.getResource(fileName);
				if (url == null) {
					cl = ErrorManager.class.getClassLoader();
					url = cl.getResource(fileName);
				}
				if (url == null && formatName.equals("antlr")) {
					rawError("ANTLR installation corrupted; cannot find ANTLR messages format file " + fileName);
					panic();
				}
				else if (url == null) {
					rawError("no such message format file " + fileName + " retrying with default ANTLR format");
					setFormat("antlr"); // recurse on this rule, trying the default message format
					return;
				}
				loadedFormat = new STGroupFile(url, "UTF-8", '<', '>');
				loadedFormat.load();

				loadedFormats.put(formatName, loadedFormat);
			}
		}

		this.formatName = formatName;
		this.format = loadedFormat;

		if (!initSTListener.errors.isEmpty()) {

View on GitHub (pinned to 7d5770395b)

Solutions

Re-download the official antlr-4.x-complete.jar from maven central and replace the broken one
Verify the jar contains org/antlr/v4/tool/templates/messages/formats/ group files: jar tf antlr-4.x-complete.jar | grep messages
Check the build plugin/dependency did not shade or minimize-jar the ANTLR tool resources away
If embedding the tool, ensure the context classloader can see ANTLR resources (Thread.currentThread().setContextClassLoader(...))

Example fix

# verify jar resources (before: missing -> corrupted)
jar tf antlr-4.13.1-complete.jar | grep 'tool/templates/messages'

# after: re-fetch the official artifact
mvn org.apache.maven.plugins:maven-dependency-plugin:3.6.1:get \
  -Dartifact=org.antlr:antlr4:4.13.1

Defensive patterns

Strategy: validation

Validate before calling

// verify the tool jar carries its message templates before invoking it
ClassLoader cl = ErrorManager.class.getClassLoader();
if (cl.getResource("org/antlr/v4/tool/templates/messages/formats/antlr.stg") == null) {
    throw new IllegalStateException("antlr jar incomplete: missing messages format file");
}

Prevention

Use the official antlr-4.x-complete.jar from Maven Central
Avoid shading/minimizing the ANTLR tool jar in build plugins
Verify jar integrity with 'jar tf ... | grep messages' after any packaging change

When it happens

Trigger: Running the ANTLR Tool (antlr4 generation) where the resources directory is missing from the jar, a shaded/repackaged jar dropped the templates, or a custom classloader (e.g. in an app server or build plugin) fails to expose the resource.

Common situations: Corrupted download of antlr-4.x-complete.jar, wrong jar on classpath, overly aggressive shading/proguard stripping resources, or running the tool with a non-standard context classloader.

Related errors

AI-assisted analysis of antlr/antlr4@7d5770395b (2026-08-14). Data as JSON: /api/errors/bcca395c0eaafbd8. Report an issue: GitHub.