diff --git a/helper/schema/data_source_resource_shim.go b/helper/schema/data_source_resource_shim.go new file mode 100644 index 000000000..7394990e1 --- /dev/null +++ b/helper/schema/data_source_resource_shim.go @@ -0,0 +1,52 @@ +package schema + +// DataSourceResourceShim takes a Resource instance describing a data source +// (with a Read implementation and a Schema, at least) and returns a new +// Resource instance with additional Create and Delete implementations that +// allow the data source to be used as a resource. +// +// This is a backward-compatibility layer for data sources that were formerly +// read-only resources before the data source concept was added. It should not +// be used for any *new* data sources. +// +// The Read function for the data source *must* call d.SetId with a non-empty +// id in order for this shim to function as expected. +// +// The provided Resource instance, and its schema, will be modified in-place +// to make it suitable for use as a full resource. +func DataSourceResourceShim(dataSource *Resource) *Resource { + // TODO: Somehow emit a warning when a shim resource is used, + // recommending that the user switch to using the data source + // instead. + + // Recursively, in-place adjust the schema so that it has ForceNew + // on any user-settable resource. + dataSourceResourceShimAdjustSchema(dataSource.Schema) + + dataSource.Create = CreateFunc(dataSource.Read) + dataSource.Delete = func(d *ResourceData, meta interface{}) error { + d.SetId("") + return nil + } + dataSource.Update = nil // should already be nil, but let's make sure + + return dataSource +} + +func dataSourceResourceShimAdjustSchema(schema map[string]*Schema) { + for _, s := range schema { + // If the attribute is configurable then it must be ForceNew, + // since we have no Update implementation. + if s.Required || s.Optional { + s.ForceNew = true + } + + // If the attribute is a nested resource, we need to recursively + // apply these same adjustments to it. + if s.Elem != nil { + if r, ok := s.Elem.(*Resource); ok { + dataSourceResourceShimAdjustSchema(r.Schema) + } + } + } +}