Custom loader and file referenced types fail to qualify name

[cpu]

👋 Hi there,

Summary

I'm trying to use go-jsonschema as a library to generate Go code from JSON schemas exposed via a dependency that offers a standard library embed.FS with the schema content. I thought this would be workable by implementing my own schemas.Loader, but in practice this doesn't seem to work. References produce errors of the form:

could not generate type for field "source": could not resolve qualified file name for common.json: cannot resolve schema "common.json"`

I've created a stand-alone reproduction here: https://github.com/cpu/schema-embed

Analysis

Looking at schemaGenerator.generateReferencedType, we can see it's calling schemas.QualifiedFileName to determine the qualified name of a referenced file:

go-jsonschema/pkg/generator/schema_generator.go

Lines 113 to 116 in 2837f3b

	qualified, qerr := schemas.QualifiedFileName(fileName, g.schemaFileName, g.config.ResolveExtensions)
	if qerr != nil {
	return nil, fmt.Errorf("could not resolve qualified file name for %s: %w", fileName, qerr)
	}

That function in turn unconditionally uses the native filesystem via os.Stat to determine if the fully qualified schema file exists:

go-jsonschema/pkg/schemas/loaders.go

Lines 203 to 205 in 2837f3b

	if !fileExists(qualified) {
	continue
	}

go-jsonschema/pkg/schemas/loaders.go

Lines 220 to 224 in 2837f3b

	func fileExists(fileName string) bool {
	_, err := os.Stat(fileName)
	return err == nil || !os.IsNotExist(err)
	}

This feels like an instance of logic that could be deferred to the Loader instance, perhaps either having schemas.Loader.Load() also return the fully qualified schema name alongside the *schemas.Schema, or by introducing a new func to the Loader interface for this purpose.

Is this something the project is interested in addressing? I could probably implement the PR myself with some guidance on the preferred solution shape. In the meantime I've reverted to expanding the embed.FS into a tempdir on the native filesystem and using the stock FileLoader. I've also confirmed that hacking out the schemas.QualifiedFileName() call in schema_generator.go and using the fileName as the qualified name "fixes" the issue for my use-case, though in the crudest way possible.

Thanks!