What causes "Unexpected end of input: ${str}" in quarkusio/quarkus?

Print and inspect the full type string reported in the message and locate where it ends prematurely

quarkusio/quarkus · error · IllegalArgumentException

Unexpected end of input: ${str}

Error message

Unexpected end of input: ${str}

What it means

TypeParser parses Java type signature strings (e.g. 'java.util.List<java.lang.String>') into Jandex type structures. This IllegalArgumentException is thrown by the unexpected() helper when the parser runs out of input while expecting another token, i.e. the type string is truncated/incomplete. The library throws it because a partial type string cannot describe a complete, well-formed type.

Source

Thrown at core/deployment/src/main/java/io/quarkus/deployment/types/TypeParser.java:180

        try {
            return Class.forName(token, true, Thread.currentThread().getContextClassLoader());
        } catch (ClassNotFoundException e) {
            throw new IllegalArgumentException("Unknown class: " + token, e);
        }
    }

    // ---

    private void expect(String expected) {
        String token = nextToken();
        if (!expected.equals(token)) {
            throw unexpected(token);
        }
    }

    private IllegalArgumentException unexpected(String token) {
        if (token.isEmpty()) {
            throw new IllegalArgumentException("Unexpected end of input: " + str);
        }
        return new IllegalArgumentException("Unexpected token '" + token + "' at position " + (pos - token.length())
                + ": " + str);
    }

    private String peekToken() {
        // skip whitespace
        while (pos < str.length() && Character.isWhitespace(str.charAt(pos))) {
            pos++;
        }

        // end of input
        if (pos == str.length()) {
            return "";
        }

        int pos = this.pos;

View on GitHub (pinned to e1c734241f)

Solutions

Print and inspect the full type string reported in the message and locate where it ends prematurely
Complete the type signature (close generics with >, finish package/class name, add array brackets)
Check the code or template that builds the string for truncation (substring, limit, line-wrap)
Validate the string parses as a Java type signature before passing it to TypeParser

Example fix

// before
new TypeParser("java.util.List<java.lang.String").parse();
// after
new TypeParser("java.util.List<java.lang.String>").parse();

Defensive patterns

Strategy: validation

Validate before calling

boolean isCompleteTypeSignature(String s) {
    if (s == null || s.isBlank()) return false;
    int depth = 0;
    for (char c : s.toCharArray()) {
        if (c == '<') depth++;
        if (c == '>') depth--;
        if (depth < 0) return false;
    }
    return depth == 0 && !s.endsWith(".") && !s.endsWith(",");
}

Try / catch

try {
    new TypeParser(sig).parse();
} catch (IllegalArgumentException e) {
    if (e.getMessage().startsWith("Unexpected end of input")) {
        throw new IllegalArgumentException("Truncated type signature: " + sig, e);
    }
    throw e;
}

Prevention

Always build signatures with helper methods, not raw string concatenation
Balance < > and [ ] brackets programmatically when composing generics
Unit-test every configured type-string before it reaches build time
Log the full signature on failure (the exception already includes it)

When it happens

Trigger: Calling TypeParser.parse/parseReferenceType/parsePrimitiveType with a string that terminates where another token is required — e.g. 'java.util.', 'java.util.List<java.util', or 'Lcom/foo/' with the closing segment missing. unexpected("") is invoked when a consumed/peeked token is empty.

Common situations: Configuration properties (e.g. quarkus config referencing custom types) where the value was cut off; generated code emitting half-built type signatures; hand-edited annotations like @ConfigMapping signatures that were truncated by templating or string slicing.

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/3416ba02775e8457. Report an issue: GitHub.