Implements $elemMatch query operator. Due to rs/rest-layer #237.

Dragomir-Ivanov · smyrman · commit 141eccb88038 · 2019-09-05T14:50:08.000+02:00
diff --git a/mongo_test.go b/mongo_test.go
@@ -425,6 +425,12 @@ func TestFind(t *testing.T) {
 		{ID: "3", Payload: map[string]interface{}{"id": "3", "name": "c", "age": 3}},
 		{ID: "4", Payload: map[string]interface{}{"id": "4", "name": "d", "age": 4}},
 		{ID: "5", Payload: map[string]interface{}{"id": "5", "name": "rest-layer-regexp"}},
+		{ID: "6", Payload: map[string]interface{}{"id": "6", "name": "f",
+			"arr": []interface{}{
+				map[string]interface{}{"a": "foo", "b": "bar"},
+				map[string]interface{}{"a": "foo", "b": "baz"},
+			},
+		}},
 	}
 	doPositiveFindTest := func(t *testing.T, h mongo.Handler, q *query.Query) *resource.ItemList {
 		l, err := h.Find(context.Background(), q)
@@ -608,4 +614,21 @@ func TestFind(t *testing.T) {
 		}
 		t.Run("then ItemList.Items should include all matching items", itemsCheckFunc(expectItems, l))
 	})
+	t.Run("when quering for array of objects match", func(t *testing.T) {
+		l := doPositiveFindTest(t, h, &query.Query{
+			Predicate: query.MustParsePredicate(`{arr:{$elemMatch:{a:"foo"}}}`),
+		})
+
+		t.Run("then ItemList.Total should be deduced correctly", totalCheckFunc(1, l))
+
+		expectItems := []*resource.Item{
+			{ID: "6", ETag: "p-6", Payload: map[string]interface{}{"id": "6", "name": "f",
+				"arr": []interface{}{
+					map[string]interface{}{"a": "foo", "b": "bar"},
+					map[string]interface{}{"a": "foo", "b": "baz"},
+				},
+			}},
+		}
+		t.Run("then ItemList.Items should include the first matching item", itemsCheckFunc(expectItems, l))
+	})
 }
diff --git a/query.go b/query.go
@@ -88,6 +88,18 @@ func translatePredicate(q query.Predicate) (bson.M, error) {
 				s = append(s, sb)
 			}
 			b["$or"] = s
+		case *query.ElemMatch:
+			s := bson.M{}
+			for _, subExp := range t.Exps {
+				sb, err := translatePredicate(query.Predicate{subExp})
+				if err != nil {
+					return nil, err
+				}
+				for k, v := range sb {
+					s[k] = v
+				}
+			}
+			b[getField(t.Field)] = bson.M{"$elemMatch": s}
 		case *query.In:
 			b[getField(t.Field)] = bson.M{"$in": t.Values}
 		case *query.NotIn:
diff --git a/query_test.go b/query_test.go
@@ -44,6 +44,7 @@ func TestTranslatePredicate(t *testing.T) {
 		{`{f:{$regex:"fo[o]{1}.+is.+some"}}`, nil, bson.M{"f": bson.M{"$regex": "fo[o]{1}.+is.+some"}}},
 		{`{$and:[{f:"foo"},{f:"bar"}]}`, nil, bson.M{"$and": []bson.M{bson.M{"f": "foo"}, bson.M{"f": "bar"}}}},
 		{`{$or:[{f:"foo"},{f:"bar"}]}`, nil, bson.M{"$or": []bson.M{bson.M{"f": "foo"}, bson.M{"f": "bar"}}}},
+		{`{f:{$elemMatch:{a:"foo",b:"bar"}}}`, nil, bson.M{"f": bson.M{"$elemMatch": bson.M{"a": "foo", "b": "bar"}}}},
 	}
 	for i := range cases {
 		tc := cases[i]

Original file line number	Diff line number	Diff line change
`@@ -44,6 +44,7 @@ func TestTranslatePredicate(t *testing.T) {`
`44`	`44`	{`{f:{$regex:"fo[o]{1}.+is.+some"}}`, nil, bson.M{"f": bson.M{"$regex": "fo[o]{1}.+is.+some"}}},
`45`	`45`	{`{$and:[{f:"foo"},{f:"bar"}]}`, nil, bson.M{"$and": []bson.M{bson.M{"f": "foo"}, bson.M{"f": "bar"}}}},
`46`	`46`	{`{$or:[{f:"foo"},{f:"bar"}]}`, nil, bson.M{"$or": []bson.M{bson.M{"f": "foo"}, bson.M{"f": "bar"}}}},
	`47`	+ {`{f:{$elemMatch:{a:"foo",b:"bar"}}}`, nil, bson.M{"f": bson.M{"$elemMatch": bson.M{"a": "foo", "b": "bar"}}}},
`47`	`48`	`}`
`48`	`49`	`for i := range cases {`
`49`	`50`	`tc := cases[i]`