Add support for the hahicorp mux library (#121)

pkg/provider/provider_mux.go

@@ -0,0 +1,69 @@
+// (C) Copyright 2021-2024 Hewlett Packard Enterprise Development LP
+
+package provider
+
+import (
+	"fmt"
+	"github.com/hashicorp/terraform-plugin-go/tfprotov5"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+
+	"github.com/hewlettpackard/hpegl-provider-lib/pkg/registration"
+)
+
+// ProviderForMux is a function that returns a list of ProviderServer functions that can be used with the
+// Hashicorp mux library.  This function will be called from terraform-provider-hpegl which will be adapted
+// to support "legacy" provider code that use SDK v2.0 (i.e. metal, vmaas, caas on PCE) as well as newer provider
+// code that uses the new Hashicorp provider "framework".
+//
+// Note that we will need to add the ProviderSchemaEntry() functions for the newer providers.  This means that
+// registration.ServiceRegistration implementations for the newer providers that only contain ProviderSchemaEntry()
+// and no SupportedResource() or SupportedDataSources().
+func ProviderForMux(reg []registration.ServiceRegistration, pf ConfigureFunc) []func() tfprotov5.ProviderServer {
+	providerSchema := generateProviderSchema(reg)
+	providerServerList := make([]func() tfprotov5.ProviderServer, 0)
+	for _, service := range reg {
+		// Only create a provider if it has resources or data sources
+		if service.SupportedResources() != nil || service.SupportedDataSources() != nil {
+			providerServerList = append(providerServerList, generateProvider(service, pf, providerSchema))
+		}
+	}
+
+	return providerServerList
+}
+
+// generateProviderSchema generates the provider schema from the service registrations.  Note that this schema
+// needs to be added to each of the sub-providers.
+func generateProviderSchema(reg []registration.ServiceRegistration) map[string]*schema.Schema {
+	providerSchema := Schema()
+	for _, service := range reg {
+		if service.ProviderSchemaEntry() != nil {
+			// We panic if the service.Name() key is repeated in providerSchema
+			if _, ok := providerSchema[service.Name()]; ok {
+				panic(fmt.Sprintf("service name %s is repeated", service.Name()))
+			}
+			providerSchema[service.Name()] = convertToTypeSet(service.ProviderSchemaEntry())
+		}
+	}
+
+	return providerSchema
+}
+
+// generateProvider will generate a sub-provider for each service that can be used with the Hashicorp mux library.
+func generateProvider(
+	service registration.ServiceRegistration,
+	pf ConfigureFunc,
+	providerSchema map[string]*schema.Schema,
+) func() tfprotov5.ProviderServer {
+	p := schema.Provider{
+		Schema:         providerSchema,
+		ResourcesMap:   service.SupportedResources(),
+		DataSourcesMap: service.SupportedDataSources(),
+		// Don't use the following field, experimental
+		ProviderMetaSchema: nil,
+		TerraformVersion:   "",
+	}
+
+	p.ConfigureContextFunc = pf(&p) // nolint staticcheck
+
+	return p.GRPCProvider
+}