lib/msgstore: protect with a mutex

MessageStore has a lot of exported fields that can be read from the outside.
Each read must be protected, because a call from Update could happen at any
time.

lib/msgstore.go

@@ -2,6 +2,7 @@ package lib
 
 import (
 	"io"
+	"sync"
 	"time"
 
 	"github.com/emersion/go-imap"
@@ -9,7 +10,10 @@ import (
 	"git.sr.ht/~sircmpwn/aerc2/worker/types"
 )
 
+// Accesses to fields must be guarded by MessageStore.Lock/Unlock
 type MessageStore struct {
+	sync.Mutex
+
 	Deleted  map[uint32]interface{}
 	DirInfo  types.DirectoryInfo
 	Messages map[uint32]*types.MessageInfo
@@ -45,6 +49,9 @@ func NewMessageStore(worker *types.Worker,
 func (store *MessageStore) FetchHeaders(uids []uint32,
 	cb func(*types.MessageInfo)) {
 
+	store.Lock()
+	defer store.Unlock()
+
 	// TODO: this could be optimized by pre-allocating toFetch and trimming it
 	// at the end. In practice we expect to get most messages back in one frame.
 	var toFetch imap.SeqSet
@@ -67,6 +74,9 @@ func (store *MessageStore) FetchHeaders(uids []uint32,
 }
 
 func (store *MessageStore) FetchFull(uids []uint32, cb func(io.Reader)) {
+	store.Lock()
+	defer store.Unlock()
+
 	// TODO: this could be optimized by pre-allocating toFetch and trimming it
 	// at the end. In practice we expect to get most messages back in one frame.
 	var toFetch imap.SeqSet
@@ -103,8 +113,7 @@ func (store *MessageStore) FetchBodyPart(
 	})
 }
 
-func (store *MessageStore) merge(
-	to *types.MessageInfo, from *types.MessageInfo) {
+func merge(to *types.MessageInfo, from *types.MessageInfo) {
 
 	if from.BodyStructure != nil {
 		to.BodyStructure = from.BodyStructure
@@ -125,6 +134,8 @@ func (store *MessageStore) merge(
 }
 
 func (store *MessageStore) Update(msg types.WorkerMessage) {
+	store.Lock()
+
 	update := false
 	switch msg := msg.(type) {
 	case *types.DirectoryInfo:
@@ -144,7 +155,7 @@ func (store *MessageStore) Update(msg types.WorkerMessage) {
 		update = true
 	case *types.MessageInfo:
 		if existing, ok := store.Messages[msg.Uid]; ok && existing != nil {
-			store.merge(existing, msg)
+			merge(existing, msg)
 		} else {
 			store.Messages[msg.Uid] = msg
 		}
@@ -186,6 +197,9 @@ func (store *MessageStore) Update(msg types.WorkerMessage) {
 		store.Uids = uids
 		update = true
 	}
+
+	store.Unlock()
+
 	if update {
 		store.update()
 	}
@@ -202,11 +216,16 @@ func (store *MessageStore) update() {
 }
 
 func (store *MessageStore) Delete(uids []uint32) {
+	store.Lock()
+
 	var set imap.SeqSet
 	for _, uid := range uids {
 		set.AddNum(uid)
 		store.Deleted[uid] = nil
 	}
+
+	store.Unlock()
+
 	store.worker.PostAction(&types.DeleteMessages{Uids: set}, nil)
 	store.update()
 }

widgets/msglist.go

@@ -53,6 +53,8 @@ func (ml *MessageList) Draw(ctx *ui.Context) {
 		return
 	}
 
+	store.Lock()
+
 	var (
 		needsHeaders []uint32
 		row          int = 0
@@ -92,6 +94,8 @@ func (ml *MessageList) Draw(ctx *ui.Context) {
 			tcell.StyleDefault, "%s", msg)
 	}
 
+	store.Unlock()
+
 	if len(needsHeaders) != 0 {
 		store.FetchHeaders(needsHeaders, nil)
 		ml.spinner.Start()
@@ -109,11 +113,13 @@ func (ml *MessageList) storeUpdate(store *lib.MessageStore) {
 		return
 	}
 
+	store.Lock()
 	if len(store.Uids) > 0 {
 		for ml.selected >= len(store.Uids) {
 			ml.Prev()
 		}
 	}
+	store.Unlock()
 
 	ml.Invalidate()
 }
@@ -139,16 +145,25 @@ func (ml *MessageList) Store() *lib.MessageStore {
 
 func (ml *MessageList) Empty() bool {
 	store := ml.Store()
+	store.Lock()
+	defer store.Unlock()
+
 	return store == nil || len(store.Uids) == 0
 }
 
 func (ml *MessageList) Selected() *types.MessageInfo {
 	store := ml.Store()
+	store.Lock()
+	defer store.Unlock()
+
 	return store.Messages[store.Uids[len(store.Uids)-ml.selected-1]]
 }
 
 func (ml *MessageList) Select(index int) {
 	store := ml.Store()
+	store.Lock()
+	defer store.Unlock()
+
 	ml.selected = index
 	for ; ml.selected < 0; ml.selected = len(store.Uids) + ml.selected {
 	}
@@ -166,6 +181,9 @@ func (ml *MessageList) Select(index int) {
 
 func (ml *MessageList) nextPrev(delta int) {
 	store := ml.Store()
+	store.Lock()
+	defer store.Unlock()
+
 	if store == nil || len(store.Uids) == 0 {
 		return
 	}