feat(rw2): prepare for RW2 support (#11101)

* feat(rw2): prepare for RW2 support

Add the RW2 proto definition to mimirpb. The implementation will follow
but it needs to patch the generated files, so we commit the proto now
to have actually readable diff in the PR that has the functionality.
See #10423 and especially #11100 diff.

* test(AddTypeToTree): allow testing for protobuf type and field number

Signed-off-by: György Krajcsovits <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: krajorama

pkg/mimirpb/compat_rw2_test.go

@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package mimirpb
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	rw2 "github.com/prometheus/prometheus/prompb/io/prometheus/write/v2"
+	"github.com/stretchr/testify/require"
+	"github.com/xlab/treeprint"
+
+	"github.com/grafana/mimir/pkg/util/test"
+)
+
+// Tests related to Prometheus Remote Write v2 (RW2) compatibility.
+
+func TestRW2TypesCompatible(t *testing.T) {
+	expectedType := reflect.TypeOf(rw2.Request{})
+	actualType := reflect.TypeOf(WriteRequestRW2{})
+
+	expectedTree := treeprint.NewWithRoot("<root>")
+	// We ignore the XXX_ fields because RW2 in Prometheus has them,
+	// but we don't. Which also means that the offsets would be different.
+	// But we are not going to cast between the two types, so offsets
+	// don't matter.
+	test.AddTypeToTree(expectedType, expectedTree, false, true, true, false)
+
+	actualTree := treeprint.NewWithRoot("<root>")
+	test.AddTypeToTree(actualType, actualTree, false, true, true, false)
+
+	// mimirpb.Sample fields order MUST match promql.FPoint so that we can
+	// cast types between them. However this makes test.RequireSameShape
+	// fail because the order is different.
+	// So we need to reverse the order of the fields in the tree.
+	// Also the name of the Timestamp field is slightly different in the
+	// two types.
+	var firstValue, secondValue string
+	rootNode, _ := actualTree.(*treeprint.Node)
+	firstValue, _ = rootNode.Nodes[1].Nodes[1].Nodes[0].Value.(string)
+	secondValue, _ = rootNode.Nodes[1].Nodes[1].Nodes[1].Value.(string)
+	rootNode.Nodes[1].Nodes[1].Nodes[0].Value = secondValue
+	rootNode.Nodes[1].Nodes[1].Nodes[1].Value = strings.ReplaceAll(firstValue, "TimestampMs", "Timestamp")
+
+	require.Equal(t, expectedTree.String(), actualTree.String(), "Proto types are not compatible")
+}