OpenAPITools/openapi-generator · error · ParserException

Negation with no negated pattern.

Error message

Negation with no negated pattern.

What it means

IgnoreLineParser throws ParserException when a line in .openapi-generator-ignore consists of exactly '!' with nothing after it. '!' negates the pattern that follows; with no negated pattern the gitignore-style rule cannot be built, so parsing fails fast.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/ignore/rules/IgnoreLineParser.java:69

        StringBuilder sb = new StringBuilder();
        String current = null;
        String next = null;

        char[] characters = text.toCharArray();
        for (int i = 0, totalLength = characters.length; i < totalLength; i++) {
            char character = characters[i];
            current = String.valueOf(character);
            next = i < totalLength - 1 ? String.valueOf(characters[i + 1]) : null;

            if (i == 0) {
                if ("#".equals(current)) {
                    //: A line starting with # serves as a comment.
                    parts.add(new Part(Token.COMMENT, text));
                    i = totalLength; // rather than early return
                    continue;
                } else if ("!".equals(current)) {
                    if (i == totalLength - 1) {
                        throw new ParserException("Negation with no negated pattern.");
                    } else {
                        parts.add(new Part(Token.NEGATE));
                        continue;
                    }
                } else if ("\\".equals(current) && "#".equals(next)) {
                    //: Put a backslash ("`\`") in front of the first hash for patterns
                    //: that begin with a hash.
                    // NOTE: Just push forward and drop the escape character. Falls through to TEXT token.
                    current = next;
                    next = null;
                    i++;
                }
            }

            if (Token.MATCH_ANY.pattern.equals(current)) {

                if (Token.MATCH_ANY.pattern.equals(next)) {
                    // peek ahead for invalid pattern. Slightly inefficient, but acceptable.

View on GitHub (pinned to fcec517be3)

Solutions

1. Delete the bare '!' line from .openapi-generator-ignore.
2. Complete the negation if one was intended, e.g. '!/docs/README.md' to re-include a file ignored by a broader pattern.
3. Scan the file for merge-conflict markers or truncated edits that left the line incomplete.

Example fix

# .openapi-generator-ignore (before):
!
/docs/**
# after:
/docs/**
!/docs/README.md

// Pre-flight: lint .openapi-generator-ignore before generation
import java.nio.file.*;

for (String line : Files.readAllLines(Paths.get(outputDir, ".openapi-generator-ignore"))) {
    if (line.trim().equals("!"))
        throw new IllegalStateException("Invalid ignore line '!' — negation with no pattern");
}

When it happens

Trigger: The .openapi-generator-ignore file in the output directory contains a line whose only character is '!' (the parser checks i == totalLength - 1 at position 0). Parsing of the ignore file aborts and generation stops.

Common situations: Hand-editing the ignore file and leaving a stray '!'; git merge-conflict leftovers; misunderstanding the syntax by assuming a lone '!' flips the default ignore behavior.

Related errors

• The pattern *** is invalid.
• Failed to generate .openapi-generator-ignore when the option
• Could not generate supporting file '{ignoreFileNameTarget}'

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/78460e177bbbdfca. Report an issue: GitHub.