Standard Library for External Data (Codelist Support)

[dschwartznyc]

Problem Description:

Rune models can rely on external data sources, such as FpML coding schemes or ISO code lists, for validating field values. In the Java implementation, this is handled by a standard CodelistLoader. The Python generator and runtime currently lack an equivalent mechanism to load, cache, and query these external data sources during validation.

Steps to Reproduce:

Example Rune code: (see codelists in CDM)[https://github.com/finos/common-domain-model/blob/master/rosetta-source/src/main/rosetta/base-staticdata-codelist-func.rosetta]

namespace cdm.base.staticdata.codelist
version "${project.version}"

func LoadCodeList: <"Loads a code list JSON resource into memory in the form of cdm.base.staticdata.codelist.CodeList Rune object">
    [codeImplementation]
    inputs:
        domain string (1..1) <"The identifier of the code list resource to retrieve. e.g. The cdm.base.staticdata.codelist.FpMLCodingScheme domain parameter">
    output:
        codelist CodeList (0..1) <"The loaded code list (or null if not found) ">

func ValidateFpMLCodingSchemeDomain: <"Validates an FpMLCodingScheme code against the resource code list defined by the domain. It leverages LoadCodeList internally.">
    [codeImplementation]
    inputs:
        code FpMLCodingScheme (1..1) <"The code to be evaluated">
        domain string (1..1) <"The code list domain">
    output:
        isValid boolean (1..1) <"The result of the external resource validation. retrieves 'True' if the code list is not found for the specified domain">

Expected Result:

A standard Python library or runtime utility should be available to handle external data loading, allowing the generator to emit consistent validation calls.

Actual Result:

Likely to be an issue like "NameError: name 'x.y.z' is not defined

Additional Context:

This has a major impact on the Common Domain Model (CDM), which uses external schemes for validating critical fields such as Business Centers. Without this support, any types using code lists will not be supported in the Python-generated CDM.

Related CDM Issues:

Issue #4277
Issue #3932
Issue #3929
Issue #3287
Issue # 3904