Expose TF schema versions for PF during tfgen (#3038)

This PR exposes the TF schema versions to PF during tfgen.

This allows us to implement tfgen-time checks for downgrades.

related to #3037
related to pulumi/pulumi-cloudflare#1156

Author: VenelinMartinov

pkg/pf/internal/schemashim/datasource.go

@@ -29,8 +29,8 @@ func (r *schemaOnlyDataSource) Schema() shim.SchemaMap {
 	return r.tf.Shim()
 }
 
-func (*schemaOnlyDataSource) SchemaVersion() int {
-	panic("DataSource SchemaVersion() should not be called during schema generation")
+func (r *schemaOnlyDataSource) SchemaVersion() int {
+	panic("datasources do not have schema versions")
 }
 
 func (r *schemaOnlyDataSource) DeprecationMessage() string {

pkg/pf/internal/schemashim/resource.go

@@ -29,8 +29,8 @@ func (r *schemaOnlyResource) Schema() shim.SchemaMap {
 	return r.tf.Shim()
 }
 
-func (*schemaOnlyResource) SchemaVersion() int {
-	panic("SchemaVersion() should not be called on a Resource during schema generation")
+func (r *schemaOnlyResource) SchemaVersion() int {
+	return int(r.tf.ResourceSchemaVersion())
 }
 
 func (r *schemaOnlyResource) DeprecationMessage() string {

pkg/pf/tests/schemashim_test.go

@@ -1157,3 +1157,24 @@ func stdProvider(resourceSchema schema.Schema) *pb.Provider {
 		}},
 	}
 }
+
+func TestSchemaVersionAccessible(t *testing.T) {
+	t.Parallel()
+
+	res := pb.NewResource(pb.NewResourceArgs{
+		Name: "r1",
+		ResourceSchema: schema.Schema{
+			Version: 2,
+		},
+	})
+
+	provider := pb.NewProvider(pb.NewProviderArgs{
+		TypeName:     "testprov",
+		AllResources: []pb.Resource{res},
+	})
+
+	shimmedProvider := schemashim.ShimSchemaOnlyProvider(context.Background(), provider)
+
+	schemaVersion := shimmedProvider.ResourcesMap().Get("testprov_r1").SchemaVersion()
+	require.Equal(t, 2, schemaVersion)
+}