Library Loading with %use only works when homeDir is not null, but invalid homeDir works fine

[fmagin]

All of the examples are on https://github.com/Kotlin/kotlin-jupyter/blob/stable-kotlin-2 but it doesn't look like this changed compared to current master

Problem

Usually I embed the kernel via

IkotlinKt.embedKernel(connectionFile, resolutionInfoProvider, Collections.singletonList(context))

but in the resulting kernel it is not possible to load a library definition, even if explicitly specifying a full path
because in:

kotlin-jupyter/src/main/kotlin/org/jetbrains/kotlinx/jupyter/libraries/LibrariesProcessorImpl.kt

Lines 66 to 67 in e512619

	val library = libraries?.resolve(libRef, vars)
	?: throw ReplException("Unknown library '$libRef'")

libraries is null, and the ReplException is thrown.

this happens because embedKernel passes null for a homeDir,

kotlin-jupyter/src/main/kotlin/org/jetbrains/kotlinx/jupyter/ikotlin.kt

Line 96 in e512619

null,

then the resolverConfig isn't created:

kotlin-jupyter/src/main/kotlin/org/jetbrains/kotlinx/jupyter/config.kt

Line 164 in e512619

resolverConfig = homeDir?.let { loadResolverConfig(it.toString(), resolutionInfoProvider) },

and then there are no libraries to pass when the LibrariesProcessor is constructed:

kotlin-jupyter/src/main/kotlin/org/jetbrains/kotlinx/jupyter/repl.kt

Line 242 in e512619

private val librariesProcessor: LibrariesProcessor = LibrariesProcessorImpl(resolverConfig?.libraries, runtimeProperties.version)

If I instead use the following code to create the kernel it works, despite the homeDir being a completely invalid directory:

        var config = KernelConfig.Companion.fromConfig(
                KernelJupyterParams.Companion.fromFile(connectionFile),
                EmptyResolutionInfoProvider.INSTANCE,
                cp,
                new File("/NOTEXISTING/"),
                true);
        IkotlinKt.kernelServer(config, ConfigKt.getDefaultRuntimeProperties(), Collections.singletonList(context));

with this I can also run %use example in the kernel, and it will correctly load the file at /home/myusername/.jupyter_kotlin/libraries/example.json, so some other code knows the default homedir anyway.

Possible Fixes

Create resolverConfig with null homeDir

loadResolverConfig has a signature that requires the homeDir to be not null

kotlin-jupyter/src/main/kotlin/org/jetbrains/kotlinx/jupyter/config.kt

Line 172 in e512619

fun loadResolverConfig(homeDir: String, resolutionInfoProvider: ResolutionInfoProvider) = ResolverConfig(defaultRepositories, getStandardResolver(homeDir, resolutionInfoProvider))

but the called getStandardResolver is fine with a homeDir of null again.

kotlin-jupyter/src/main/kotlin/org/jetbrains/kotlinx/jupyter/libraries/resolutionUtil.kt

Lines 14 to 21 in e512619

	fun getStandardResolver(homeDir: String? = null, infoProvider: ResolutionInfoProvider): LibraryResolver {
	// Standard resolver doesn't cache results in memory
	var res: LibraryResolver = FallbackLibraryResolver
	val librariesDir: File? = homeDir?.let { KERNEL_LIBRARIES.homeLibrariesDir(File(it)) }
	res = LocalLibraryResolver(res, librariesDir)
	res = DefaultInfoLibraryResolver(res, infoProvider, listOf(KERNEL_LIBRARIES.userLibrariesDir))
	return res
	}

Change the signature of embedKernel to allow passing a homeDir

I don't know what this homeDir value actually achieves, and it might be useful for code using embedKernel to correctly set this. But because a null homeDir doesn't raise an issues in my case it should probably be an optional parameter. And then it should IMO still be possible to load library definitions from a full path or from the .jupyter_kotlin/libraries/ directory even if no homeDir is passed.