Snapshot stream rejects the 32-character digest issued for multi-document namespaces #6590

package client

import (
	"testing"
	"testing/fstest"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/mock"
	"github.com/stretchr/testify/require"
	"go.flipt.io/flipt/internal/server/environments"
	"go.flipt.io/flipt/internal/server/evaluation"
	storagefs "go.flipt.io/flipt/internal/storage/fs"
	rpcevaluation "go.flipt.io/flipt/rpc/v2/evaluation"
	"go.uber.org/zap/zaptest"
)

func TestEvaluationSnapshotNamespaceStream_MultiDocumentDigest(t *testing.T) {
	logger := zaptest.NewLogger(t)
	src := fstest.MapFS{
		"a/features.yaml": {Data: []byte("namespace:\n  key: default\nflags:\n- key: flag_a\n  name: A\n  type: BOOLEAN_FLAG_TYPE\n  enabled: true\n")},
		"b/features.yaml": {Data: []byte("namespace:\n  key: default\nflags:\n- key: flag_b\n  name: B\n  type: BOOLEAN_FLAG_TYPE\n  enabled: true\n")},
	}

	snap, err := storagefs.SnapshotFromPaths(logger, src, []string{"a/features.yaml", "b/features.yaml"})
	require.NoError(t, err)
	nsSnap, err := snap.EvaluationNamespaceSnapshot(t.Context(), "default")
	require.NoError(t, err)
	require.Len(t, nsSnap.Flags, 2)
	t.Logf("digest=%q len=%d", nsSnap.Digest, len(nsSnap.Digest))
	require.Len(t, nsSnap.Digest, 32)

	mockEnv := environments.NewMockEnvironment(t)
	envStore := evaluation.NewMockEnvironmentStore(t)
	mockEnv.On("Key").Return("env-key").Maybe()
	envStore.On("Get", mock.Anything, "env-key").Return(mockEnv, nil).Maybe()
	mockEnv.On("EvaluationNamespaceSnapshotSubscribe", mock.Anything, "default", mock.Anything).Return(&fakeCloser{}, nil).Run(func(args mock.Arguments) {
		ch := args.Get(2).(chan<- *rpcevaluation.EvaluationNamespaceSnapshot)
		go func() { ch <- nsSnap; close(ch) }()
	}).Maybe()

	stream := &mockStream{ctx: t.Context()}
	stream.On("Send", mock.Anything).Return(nil).Maybe()
	s := NewServer(logger, envStore)
	d := nsSnap.Digest
	err = s.EvaluationSnapshotNamespaceStream(&rpcevaluation.EvaluationNamespaceSnapshotStreamRequest{
		EnvironmentKey: "env-key", Key: "default", Digest: &d,
	}, stream)
	// Expected behavior: resuming with the server-issued digest is accepted and the unchanged snapshot is not resent.
	assert.NoError(t, err)
	assert.Empty(t, stream.sent)
}