Comparing OpenAPI 3.0.1 to 3.1.0 does not work

When running a comparison between OpenAPI 3.0.1 and 3.1.0 via Docker, it looks like everything is reported as different.

Suppressing the details gives this:

$ docker run --rm -t -v .:/specs:ro  openapitools/openapi-diff /specs/api-docs-301.json /specs/api-docs-310.json --state
incompatible

ℹ Please note that those spec files are identical, only the initial OpenAPI version differs:

• "openapi": "3.0.1"
• "openapi": "3.1.0"

Comparing two specs with OpenAPI 3.1.0 seems to work as desired. ✅

I used latest which appears to be 6 weeks old - cannot get the version from the tool itself 🤷

Running the same via openapi-diff installed from brew shows a different error:

$ openapi-diff api-docs-301.json api-docs-310.json 
Unexpected exception. Reason: Cannot read new OpenAPI spec
java.lang.RuntimeException: Cannot read new OpenAPI spec
        at org.openapitools.openapidiff.core.OpenApiCompare.notNull(OpenApiCompare.java:107)
        at org.openapitools.openapidiff.core.OpenApiCompare.fromSpecifications(OpenApiCompare.java:102)
        at org.openapitools.openapidiff.core.OpenApiCompare.fromLocations(OpenApiCompare.java:91)
        at org.openapitools.openapidiff.cli.Main.main(Main.java:174)

But this also does not work with two OpenAPI 3.1.0 specs:

$ openapi-diff api-docs-310.json api-docs-310.json 
Unexpected exception. Reason: Cannot read old OpenAPI spec
java.lang.RuntimeException: Cannot read old OpenAPI spec

Brew shows this to be version 2.0.1 - cannot get the version from the tool itself.

Start with the CLI entry point in Main.java and the specification-loading path in OpenApiCompare.java, especially the calls shown in the stack traces. Reproduce the Docker and brew commands with identical 3.0.1 and 3.1.0 documents, then compare their behavior. Done means valid comparisons work across these versions without reporting identical documents as incompatible or failing to read them.