[BUG][JAVA] Generate from spec within JAR-dependency - File found then File _not found_

Description

When migrated from swagger-codegen-maven-plugin to openapi-generator-maven-plugin we are no longer able to generate Java code from an OpenAPI specification located in a Maven JAR-dependency. The specification file is first found, then at a later stage it's no longer found.

Please note that the codegen is successful with the exact same configuration if I put the api.yml in the local project and point <inputSpec> to the local file, e.g.

<inputSpec>${project.basedir}/src/main/resources/api.yml</inputSpec>

Hence:

• The OpenAPI 3.0.2 YML file is correct.
• The generator (maven plugin) configuration is OK.

Detailed Description

When building verbose I can see that the generator first prints my YML-file (api.yml) as JSON (OK):

{
  "openapi" : "3.0.2",
  "info" : {
    "title" : "Example API",
    "description" : "Example API",
    "contact" : {
      "name" : "John Doe",
      "email" : "john.doe@example.com"
    },
    "version" : "1.0"
  },
...
}

Then writing model files (schemas), e.g.

[INFO] writing file C:\code\example-impl\functions\target\generated-sources\swagger\com\example\api\model\SomeModel.java

Then Model Info is printed (OK):

############ Model info ############
{...}

Then Supporting file info is printed (OK):

############ Supporting file info ############`
{...}

Then writing supporting files:

[INFO] writing file C:\code\example-impl\functions\target\generated-sources\swagger/com/example/api\ApiClient.java
[INFO] writing file C:\code\example-impl\functions\target\generated-sources\swagger/com/example/api\ApiException.java
...

So far everything looks ok and the YML-file has obviously been found by the plugin. But directly after the supporting files have been generated I get a FileNotFoundException:

[ERROR] C:\code\example-impl\api.yml [0:0]: unexpected error in Open-API generation
java.io.FileNotFoundException: api.yml (The system cannot find the file specified)
	at java.io.FileInputStream.open0(Native Method)
	at java.io.FileInputStream.open(FileInputStream.java:195)
	at java.io.FileInputStream.<init>(FileInputStream.java:138)
	at com.google.common.io.Files$FileByteSource.openStream(Files.java:129)
	at com.google.common.io.Files$FileByteSource.openStream(Files.java:119)
	at com.google.common.io.ByteSource.copyTo(ByteSource.java:245)
	at com.google.common.io.ByteSource.hash(ByteSource.java:329)
	at org.openapitools.codegen.plugin.CodeGenMojo.execute(CodeGenMojo.java:637)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.MojoExecutor.executeForkedExecutions(MojoExecutor.java:352)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:197)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
	at org.codehaus.classworlds.Launcher.main(Launcher.java:47)
[ERROR] 
java.io.FileNotFoundException: api.yml (The system cannot find the file specified)
	at java.io.FileInputStream.open0(Native Method)
	at java.io.FileInputStream.open(FileInputStream.java:195)
	at java.io.FileInputStream.<init>(FileInputStream.java:138)
	at com.google.common.io.Files$FileByteSource.openStream(Files.java:129)
	at com.google.common.io.Files$FileByteSource.openStream(Files.java:119)
	at com.google.common.io.ByteSource.copyTo(ByteSource.java:245)
	at com.google.common.io.ByteSource.hash(ByteSource.java:329)
	at org.openapitools.codegen.plugin.CodeGenMojo.execute(CodeGenMojo.java:637)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.MojoExecutor.executeForkedExecutions(MojoExecutor.java:352)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:197)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
	at org.codehaus.classworlds.Launcher.main(Launcher.java:47)

The maven plugin is located at C:\code\example-impl\functions\pom.xml
I run mvn clean install from C:\code\example-impl\ which has a parent pom.xml to the functions\pom.xml (functions is a module).
One thing I noticed is that the error message above looks for the file at C:\code\example-impl\api.yml, i.e. the folder of the POM I'm running. If I run mvn clean install on the module POM C:\code\example-impl\functions\pom.xml then it's the same error, but it now fails with:

[ERROR] C:\code\example-impl\functions\api.yml [0:0]: unexpected error in Open-API generation
java.io.FileNotFoundException: api.yml (The system cannot find the file specified)
	at java.io.FileInputStream.open0(Native Method)

The file is inside the JAR-dependency, not on any of the project paths.

My plugin definition:

In C:\code\example-impl\functions\pom.xml:

      <plugin>
        <groupId>org.openapitools</groupId>
        <artifactId>openapi-generator-maven-plugin</artifactId>
        <version>3.3.4</version>
        <dependencies>
          <dependency>
            <groupId>com.example</groupId>
            <artifactId>example-api</artifactId>
            <version>${example-api.version}</version>
          </dependency>
        </dependencies>
        <executions>
          <execution>
            <goals>
              <goal>generate</goal>
            </goals>
            <configuration>
              <validateSpec>true</validateSpec>
              <inputSpec>api.yml</inputSpec>
              <generatorName>java</generatorName>
              <modelNamePrefix>ExApi</modelNamePrefix>
              <verbose>true</verbose>
              <configOptions>
                <sourceFolder>swagger</sourceFolder>
                <dateLibrary>java8</dateLibrary>
              </configOptions>
              <typeMappings>
                <typeMapping>OffsetDateTime=Instant</typeMapping>
              </typeMappings>
              <importMappings>
                <importMapping>java.time.OffsetDateTime=java.time.Instant</importMapping>
              </importMappings>
              <library>jersey2</library>
              <output>${project.build.directory}/generated-sources</output>
              <modelPackage>${default.package}.api.model</modelPackage>
              <generateModels>true</generateModels>
              <generateApis>false</generateApis>
              <generateApiTests>false</generateApiTests>
              <generateApiDocumentation>false</generateApiDocumentation>
              <generateModelTests>false</generateModelTests>
              <generateModelDocumentation>false</generateModelDocumentation>
            </configuration>
          </execution>
        </executions>
      </plugin>

openapi-generator version

3.3.4

OpenAPI declaration file content or url

N/A

Steps to reproduce

See description.

Related issues/PRs

None found.

Suggest a fix

Start with CodeGenMojo.execute at line 637 and the plugin configuration in functions/pom.xml, focusing on how inputSpec api.yml from the JAR dependency is later opened or hashed. Reproduce with mvn clean install from the parent or module directory; done means generation completes without FileNotFoundException for the dependency-contained specification.