What causes "Incomplete escape sequence at the end of input in glob %s" in quarkusio/quarkus?

Remove the trailing backslash or escape it explicitly ('\\') if a literal backslash is intended

quarkusio/quarkus · error · IllegalStateException

Incomplete escape sequence at the end of input in glob %s

Error message

Incomplete escape sequence at the end of input in glob %s

What it means

GlobUtil.unescape() throws IllegalStateException when a backslash is the last character of the glob pattern with nothing following to unescape. An escape sequence requires at least one character after the backslash, so a trailing '\' is incomplete input.

Source

Thrown at independent-projects/bootstrap/app-model/src/main/java/io/quarkus/util/GlobUtil.java:145

                    i--;
                    i = glob(glob, i, length, ",}", result);
                    break;
            }
        }
        throw new IllegalStateException(String.format("Missing } at the end of input in glob %s", glob));
    }

    private static int unescape(String glob, int i, int length, StringBuilder result, boolean charClass) {
        if (i < length) {
            final char current = glob.charAt(i++);
            if (charClass) {
                escapeCharClassIfNeeded(current, result);
            } else {
                escapeIfNeeded(current, result);
            }
            return i;
        } else {
            throw new IllegalStateException(
                    String.format("Incomplete escape sequence at the end of input in glob %s", glob));
        }
    }

    private static int charClass(String glob, int i, int length, StringBuilder result) {
        result.append("[[^/]&&[");
        if (i < length && glob.charAt(i) == '!') {
            i++;
            result.append('^');
        }
        while (i < length) {
            char current = glob.charAt(i++);
            switch (current) {
                case ']':
                    result.append("]]");
                    return i;
                case '-':
                    result.append('-');

View on GitHub (pinned to e1c734241f)

Solutions

Remove the trailing backslash or escape it explicitly ('\\') if a literal backslash is intended
Use forward slashes in glob patterns ('path/to/**') since globs are not Windows-path aware
Check upstream string building so the character after '\' is not stripped by another escaping layer

Example fix

// before
GlobUtil.toRegexPattern("src/main\\");
// after
GlobUtil.toRegexPattern("src/main/**");

Defensive patterns

Strategy: validation

Validate before calling

static boolean endsWithCompleteEscape(String glob) {
    int backslashes = 0;
    for (int i = glob.length() - 1; i >= 0 && glob.charAt(i) == '\\'; i--) backslashes++;
    return backslashes % 2 == 0;
}

Try / catch

try {
    return GlobUtil.toRegexPattern(glob);
} catch (IllegalStateException e) {
    if (e.getMessage().startsWith("Incomplete escape sequence")) {
        throw new IllegalArgumentException("Trailing backslash in glob: " + glob, e);
    }
    throw e;
}

Prevention

Use forward slashes in glob patterns instead of Windows backslashes
When escaping is needed, ensure the escaped character survives any upstream string escaping (config files, templates, shells)
Reject or repair patterns ending in an odd number of backslashes before use

When it happens

Trigger: Passing a glob ending in '\', e.g. 'path\to\' or 'foo\', to GlobUtil; unescape is reached from glob() or charClass() whenever it consumes a backslash at end of input.

Common situations: Windows-style path separators used in patterns instead of '/'; string concatenation or templating that dropped the final escaped character (e.g. 'foo\*' losing the '*'); shell/config escaping layers eating the trailing char.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/8bee44af4095579b. Report an issue: GitHub.