[BUG] [JAVA] error: too many parameters

[blaghed]

Description

After upgrading from 7.3.0, we started getting error: too many parameters on a generated POJO Model of an object that has 255 fields.
Tracked it down to Java/pojo.mustache)

We've tried manually setting x-java-all-args-constructor: false and x-has-readonly-properties: false, but these result in the same error.
As far as I can tell, x-java-all-args-constructor is respected, but x-has-readonly-properties is superseded by the property being read only itself -- which makes sense (see AbstractJavaCodegen.java).

As such, we're unable to instruct the generator to not add these constructors at all.
I understand this was done to fix an issue with Jackson (see #18870 ), but sadly it brings this issue on the other side.

openapi-generator version

7.9.0

Suggest a fix

Issue: Java/pojo.mustache)
Commit: #18870

[jpfinne]

@blaghed

This can be fixed by a small change in AbstractJavaCodeGen.java

protected int constructorWithAllArgsMaxArguments=254;

protected boolean isConstructorWithAllArgsAllowed(CodegenModel codegenModel) {
    return (this.generateConstructorWithAllArgs &&
            (!codegenModel.vars.isEmpty() || codegenModel.parentVars.isEmpty()) &&
            cm.vars.size() + cm.parentVars.size() <= constructorWithAllArgsMaxArguments;
}

can you create a PR with that change?

[blaghed]

The error happens on the read-only constructor, though. The "all args" one can be disabled correctly.
At the moment I am working around this by adding a vendor extension on the pojo.mustache to allow disabling.

[jpfinne]

Maybe this:

if (property.isReadOnly && property.readOnlyVars.size() <= 255) {
    model.getVendorExtensions().put("x-has-readonly-properties", true);
}

[blaghed]

That's reasonable. This won't bring back whatever issue with Jackson was fixed? I assume it needs some way to write these properties, and no setters are present since they are read-only.