Allow schema.Reference to work on array of ids. Closes rs#222. Closes rs#223

Author: Dragomir-Ivanov

rest/resource.go

@@ -34,7 +34,11 @@ func (r restResource) MultiGet(ctx context.Context, ids []interface{}) ([]map[st
 	}
 	payloads := make([]map[string]interface{}, 0, len(items))
 	for _, i := range items {
-		payloads = append(payloads, i.Payload)
+		var p map[string]interface{}
+		if i != nil {
+			p = i.Payload
+		}
+		payloads = append(payloads, p)
 	}
 	return payloads, nil
 }

schema/query/projection_evaluator.go

@@ -79,18 +79,37 @@ func evalProjection(ctx context.Context, p Projection, payload map[string]interf
 					}
 				} else if ref, ok := def.Validator.(*schema.Reference); ok {
 					// Execute sub-request in batch
+					var e Expression
+					v, isArray := val.([]interface{})
+					if isArray {
+						e = &In{Field: "id", Values: v}
+					} else {
+						e = &Equal{Field: "id", Value: val}
+					}
 					q := &Query{
 						Projection: pf.Children,
-						Predicate:  Predicate{&Equal{Field: "id", Value: val}},
+						Predicate:  Predicate{e},
 					}
 					rbr.request(ref.Path, q, func(payloads []map[string]interface{}, validator schema.Validator) error {
 						var v interface{}
-						if len(payloads) == 1 {
-							payload, err := evalProjection(ctx, pf.Children, payloads[0], validator, rbr)
-							if err != nil {
-								return fmt.Errorf("%s: error applying Projection on sub-field: %v", name, err)
+						if len(payloads) == 1 && isArray == false {
+							if payloads[0] != nil {
+								payload, err := evalProjection(ctx, pf.Children, payloads[0], validator, rbr)
+								if err != nil {
+									return fmt.Errorf("%s: error applying Projection on sub-field: %v", name, err)
+								}
+								if v, err = resolveFieldHandler(ctx, pf, def, payload); err != nil {
+									return fmt.Errorf("%s: error resolving field handler on sub-field: %v", name, err)
+								}
+							}
+						} else {
+							var err error
+							for i := range payloads {
+								if payloads[i], err = evalProjection(ctx, pf.Children, payloads[i], validator, rbr); err != nil {
+									return fmt.Errorf("%s: error applying projection on sub-field item #%d: %v", pf.Name, i, err)
+								}
 							}
-							if v, err = resolveFieldHandler(ctx, pf, def, payload); err != nil {
+							if v, err = resolveFieldHandler(ctx, pf, def, payloads); err != nil {
 								return fmt.Errorf("%s: error resolving field handler on sub-field: %v", name, err)
 							}
 						}

schema/query/projection_evaluator_test.go

@@ -101,10 +101,10 @@ func TestProjectionEval(t *testing.T) {
 					"ref":  {},
 				}},
 				payloads: map[string]map[string]interface{}{
-					"1": map[string]interface{}{"name": "first"},
-					"2": map[string]interface{}{"name": "second", "ref": "a"},
-					"3": map[string]interface{}{"name": "third", "ref": "b"},
-					"4": map[string]interface{}{"name": "forth", "ref": "a"},
+					"1": map[string]interface{}{"id": "1", "name": "first"},
+					"2": map[string]interface{}{"id": "2", "name": "second", "ref": "a"},
+					"3": map[string]interface{}{"id": "3", "name": "third", "ref": "b"},
+					"4": map[string]interface{}{"id": "4", "name": "forth", "ref": "a"},
 				},
 			},
 		},
@@ -186,6 +186,48 @@ func TestProjectionEval(t *testing.T) {
 			nil,
 			`{"reference":{"name":"second"}}`,
 		},
+		{
+			"Reference-no-expansion",
+			`reference`,
+			`{"reference":"100"}`,
+			nil,
+			`{"reference":"100"}`,
+		},
+		{
+			"Reference-non-existant",
+			`reference{name}`,
+			`{"reference":"100"}`,
+			nil,
+			`{"reference":null}`,
+		},
+		{
+			"ReferenceArray-non-existant",
+			`reference{name}`,
+			`{"reference":["100"]}`,
+			nil,
+			`{"reference":[]}`,
+		},
+		{
+			"ReferenceArray-empty",
+			`reference{name}`,
+			`{"reference":[]}`,
+			nil,
+			`{"reference":[]}`,
+		},
+		{
+			"ReferenceArray-one",
+			`reference{name}`,
+			`{"reference":["2"]}`,
+			nil,
+			`{"reference":[{"name":"second"}]}`,
+		},
+		{
+			"ReferenceArray-many",
+			`reference{name}`,
+			`{"reference":["2","3"]}`,
+			nil,
+			`{"reference":[{"name":"second"},{"name":"third"}]}`,
+		},
 		{
 			"Connection#1",
 			`connection{name}`,