[BUG] Using external references in OpenAPI spec

Bug Report Checklist

If external file references are used in an OpenAPI spec file, an error is thrown by a utility function. Failed to get the schema name: ../../shared/requests/submit.yaml#/components/schemas/SubmitSuccessResponseV1
(This value is particular to my input. In general, it prints the name of the external reference file#/component-name)

It originates here: https://github.com/OpenAPITools/openapi-generator/blob/4b493358a882171781e239af2582679ec39aa552/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java#L393

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

openapi-generator version

I'm building the tip of master brach at 4b49335

OpenAPI declaration file content or url

I can reproduce the issue with this file: https://github.com/ripple/rippled-api-spec/blob/main/open_api/json_api.yaml

I suspect that any OpenAPI input file that uses $ref in an external file, will see this problem. I'm using OpenAPI v3.1.0

Generation Details

1. mvn clean package -DSkipTests
2. java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g python -i ../rippled-api-spec/open_api/json_api.yaml -o sample-python-out-jul25-fresh --skip-validate-spec

Here is the observed log from the code-generator:
external-ref.log

Steps to reproduce

Related issues/PRs

couldn't find related issues

Suggest a fix

public static String getSimpleRef(String ref) {
        // a reference to an external file
        if (ref != NULL && ref.contains(".yaml#/")) {
            // strip the filePath portion of the reference, only retain the #/component or #/definition portion
            ref = ref.subString(ref.lastIndexOf(".yaml#/") + 5)
        }
        
        // ... continue with the rest of the function as-is

Start in modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java around line 393 and reproduce with ripple/rippled-api-spec's open_api/json_api.yaml. Run the Maven build and Python generation command from the issue, then inspect how the external $ref is parsed. Done means generation handles the external reference without the reported schema-name error.