internal/legacy/helper/schema

moving helper/schema into the ineternal/legacy tree

internal/legacy/helper/schema/data_source_resource_shim.go

@@ -0,0 +1,59 @@
+package schema
+
+import (
+	"fmt"
+)
+
+// 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(name string, dataSource *Resource) *Resource {
+	// 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
+
+	// FIXME: Link to some further docs either on the website or in the
+	// changelog, once such a thing exists.
+	dataSource.DeprecationMessage = fmt.Sprintf(
+		"using %s as a resource is deprecated; consider using the data source instead",
+		name,
+	)
+
+	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)
+			}
+		}
+	}
+}