From 6b8d1502de99dc9b039b7cab04547a263610db7e Mon Sep 17 00:00:00 2001
From: Patryk Kwiatek <patryk@kwiatek.xyz>
Date: Mon, 13 Nov 2023 11:22:38 +0100
Subject: [PATCH] Add test for tailable cursor with non-capped collection
 (#3677)

---
 integration/query_test.go            | 18 ++++++++++++++++
 internal/handlers/common/find.go     |  2 +-
 internal/handlers/sqlite/msg_find.go | 32 ++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/integration/query_test.go b/integration/query_test.go
index 4542003b1442..948088612617 100644
--- a/integration/query_test.go
+++ b/integration/query_test.go
@@ -1203,3 +1203,21 @@ func TestQueryShowRecordIDErrors(t *testing.T) {
 		})
 	}
 }
+
+func TestQueryTailableCursors(t *testing.T) {
+	t.Parallel()
+
+	ctx, collection := setup.Setup(t)
+	_, err := collection.InsertOne(ctx, bson.D{{"v", int32(42)}})
+	require.NoError(t, err)
+
+	expectedErr := mongo.CommandError{
+		Code: 2,
+		Message: "error processing query: ns=TestQueryTailableCursors.TestQueryTailableCursorsTree:" +
+			"  $eq null\nSort: {}\nProj: {}\n tailable cursor requested on non capped collection",
+		Name: "BadValue",
+	}
+
+	_, err = collection.Find(ctx, bson.D{{}}, options.Find().SetCursorType(options.Tailable))
+	AssertEqualCommandError(t, expectedErr, err)
+}
diff --git a/internal/handlers/common/find.go b/internal/handlers/common/find.go
index 4387c3054c55..b2567ab9b1d5 100644
--- a/internal/handlers/common/find.go
+++ b/internal/handlers/common/find.go
@@ -39,6 +39,7 @@ type FindParams struct {
 	SingleBatch bool            `ferretdb:"singleBatch,opt"`
 	Comment     string          `ferretdb:"comment,opt"`
 	MaxTimeMS   int64           `ferretdb:"maxTimeMS,opt,wholePositiveNumber"`
+	Tailable    bool            `ferretdb:"tailable,opt"`
 
 	Collation *types.Document `ferretdb:"collation,unimplemented"`
 	Let       *types.Document `ferretdb:"let,unimplemented"`
@@ -52,7 +53,6 @@ type FindParams struct {
 
 	ReturnKey           bool `ferretdb:"returnKey,unimplemented-non-default"`
 	ShowRecordId        bool `ferretdb:"showRecordId,opt"`
-	Tailable            bool `ferretdb:"tailable,unimplemented-non-default"`
 	OplogReplay         bool `ferretdb:"oplogReplay,unimplemented-non-default"`
 	NoCursorTimeout     bool `ferretdb:"noCursorTimeout,unimplemented-non-default"`
 	AwaitData           bool `ferretdb:"awaitData,unimplemented-non-default"`
diff --git a/internal/handlers/sqlite/msg_find.go b/internal/handlers/sqlite/msg_find.go
index 2f5ab567ceec..596f10a1798d 100644
--- a/internal/handlers/sqlite/msg_find.go
+++ b/internal/handlers/sqlite/msg_find.go
@@ -66,6 +66,38 @@ func (h *Handler) MsgFind(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg, er
 		return nil, lazyerrors.Error(err)
 	}
 
+	if params.Tailable {
+		var res *backends.ListCollectionsResult
+		var collInfo *backends.CollectionInfo
+
+		res, err = db.ListCollections(ctx, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		// TODO https://github.com/FerretDB/FerretDB/issues/3601
+		for _, coll := range res.Collections {
+			if coll.Name == params.Collection {
+				collInfo = &coll
+			}
+		}
+
+		if collInfo != nil && !collInfo.Capped() {
+			return nil, commonerrors.NewCommandErrorMsgWithArgument(
+				commonerrors.ErrBadValue,
+				fmt.Sprintf(
+					"error processing query: ns=%s.%sTree:"+
+						"  $eq null\nSort: {}\nProj: {}\n tailable cursor requested on non capped collection",
+					params.DB,
+					params.Collection,
+				),
+				"find",
+			)
+		}
+
+		return nil, common.Unimplemented(document, "tailable")
+	}
+
 	qp := &backends.QueryParams{
 		Comment: params.Comment,
 	}