[BUG] Failing generation with PatternSyntaxException for security with - apiKey: []

Bug Report Checklist

• [y ] Have you provided a full/minimal spec to reproduce the issue?
• [y] Have you validated the input using an OpenAPI validator (example)?
• [n]Have you tested with the latest master to confirm the issue still exists?
  DOES NOT BUILD, REQUIRES "org.gradle:gradle-tooling-api🫙7.6" WHICH DOES NOT EXIST IN MY WORLD
• [y ] Have you searched for related issues/PRs?
• [y ] What's the actual output vs expected output?
• [n ] [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

This definition is copied from the documentation https://swagger.io/docs/specification/authentication/api-keys/ and leads to a generation error:

security:
- apiKey: []
- appId: []

[ERROR]
java.util.regex.PatternSyntaxException: Unclosed character class near index 22
^- apiKey: [[^\\]&&[]]$

The definition with space in between the brackets works:

security:
- apiKey: [ ]
- appId: [ ]

But even this fails with slightly older libraries (which exactly: don't know)

openapi-generator version

6.3.0
also 6.1.0

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  version: 0.0.1
  title: Bugreport
  description: API key openapitools demonstration
servers:
  - url: http://localhost:8080/v3/api-docs/
  - url: http://localhost:8080/swagger-ui.html
paths:
  /example:
    get:
      operationId: listVersionsv2
      summary: List API versions
      responses:
        '200':
          description: OK
        '401':
          description: Authorization failed
      security:
        - apiKey: []
        - appId: []
components:
  securitySchemes:
    apiKey:
      type: apiKey
      in: header
      name: X-API-KEY
    appId:
      type: apiKey
      in: header
      name: X-APP-ID

Generation Details

With mvn install.

Output:

[ERROR]
java.util.regex.PatternSyntaxException: Unclosed character class near index 22
^- apiKey: [[^\\]&&[]]$
                      ^
    at java.util.regex.Pattern.error (Pattern.java:2028)
    at java.util.regex.Pattern.clazz (Pattern.java:2690)
    at java.util.regex.Pattern.clazz (Pattern.java:2658)
    at java.util.regex.Pattern.sequence (Pattern.java:2139)
    at java.util.regex.Pattern.expr (Pattern.java:2069)
    at java.util.regex.Pattern.compile (Pattern.java:1783)
    at java.util.regex.Pattern.<init> (Pattern.java:1430)
    at java.util.regex.Pattern.compile (Pattern.java:1095)
    at sun.nio.fs.WindowsFileSystem.getPathMatcher (WindowsFileSystem.java:282)
    at org.openapitools.codegen.ignore.rules.FileRule.<init> (FileRule.java:30)
    at org.openapitools.codegen.ignore.rules.Rule.create (Rule.java:115)
    at org.openapitools.codegen.ignore.CodegenIgnoreProcessor.loadCodegenRules (CodegenIgnoreProcessor.java:121)
    at org.openapitools.codegen.ignore.CodegenIgnoreProcessor.loadFromFile (CodegenIgnoreProcessor.java:82)
    at org.openapitools.codegen.ignore.CodegenIgnoreProcessor.<init> (CodegenIgnoreProcessor.java:76)
    at org.openapitools.codegen.DefaultGenerator.opts (DefaultGenerator.java:148)
    at org.openapitools.codegen.plugin.CodeGenMojo.execute (CodeGenMojo.java:837)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:370)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:351)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:215)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:171)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:163)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:294)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:960)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:293)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:196)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:77)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:568)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  14.093 s
[INFO] Finished at: 2023-02-16T11:56:11+01:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.openapitools:openapi-generator-maven-plugin:6.3.0:generate (bugreport-example-client) on project apikey-security-fails: Code generation failed. See above for the full exception. -> [Help 1]

My build definition for reference.

    <build>
        <sourceDirectory>src/main/java</sourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <!-- plugin configuration added for bug report -->
            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>${openapi-generator-version}</version>
                <executions>
                    <execution>
                        <id>bugreport-example-client</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.basedir}/src/main/resources/apiKey-openapitools-bug.yaml</inputSpec>
                            <generatorName>spring</generatorName>
                            <library>spring-cloud</library>
                            <apiPackage>nl.bugreport.api</apiPackage>
                            <modelPackage>nl.bugreport.model</modelPackage>
                            <ignoreFileOverride>${project.basedir}/src/main/resources/apiKey-openapitools-bug.yaml</ignoreFileOverride>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

My local example project is based on Spring Boot 2.7.7 and uses the newest available packages apart from that.

Steps to reproduce

Generate code.

Related issues/PRs

To my knowledge none.

Suggest a fix

Apparently the regular expression or the regex library has a bug.

Start with org.openapitools.codegen.ignore.rules.FileRule and the loading path through Rule.create, CodegenIgnoreProcessor.loadCodegenRules, and DefaultGenerator.opts. Reproduce the Maven generation using the supplied OpenAPI declaration and ignoreFileOverride, then trace how the empty security arrays reach the file-rule pattern handling. Done means generation completes successfully for the reported specification without the PatternSyntaxException.