From 8f404e0a469992c640faaab65f8b840ba0b4beb1 Mon Sep 17 00:00:00 2001
From: Qi Xiao <xiaqqaix@gmail.com>
Date: Thu, 8 Sep 2016 18:15:09 +0200
Subject: [PATCH] Synchronize access to command history from editor.

---
 edit/editor.go        |  3 +++
 edit/history-value.go | 14 +++++++++++++-
 edit/history.go       |  2 ++
 edit/module.go        |  2 +-
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/edit/editor.go b/edit/editor.go
index 48284972..50999bc5 100644
--- a/edit/editor.go
+++ b/edit/editor.go
@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"sync"
 	"syscall"
 	"time"
 
@@ -40,6 +41,8 @@ type Editor struct {
 	rpromptPersistent bool
 	beforeReadLine    eval.Variable
 
+	historyMutex sync.RWMutex
+
 	editorState
 }
 
diff --git a/edit/history-value.go b/edit/history-value.go
index c594c678..ebd4e1a0 100644
--- a/edit/history-value.go
+++ b/edit/history-value.go
@@ -1,12 +1,15 @@
 package edit
 
 import (
+	"sync"
+
 	"github.com/elves/elvish/eval"
 	"github.com/elves/elvish/store"
 )
 
 type History struct {
-	st *store.Store
+	mutex *sync.RWMutex
+	st    *store.Store
 }
 
 var _ eval.ListLike = History{}
@@ -20,12 +23,18 @@ func (hv History) Repr(int) string {
 }
 
 func (hv History) Len() int {
+	hv.mutex.RLock()
+	defer hv.mutex.RUnlock()
+
 	nextseq, err := hv.st.NextCmdSeq()
 	maybeThrow(err)
 	return nextseq - 1
 }
 
 func (hv History) Iterate(f func(eval.Value) bool) {
+	hv.mutex.RLock()
+	defer hv.mutex.RUnlock()
+
 	n := hv.Len()
 	for i := 1; i <= n; i++ {
 		s, err := hv.st.Cmd(i)
@@ -37,6 +46,9 @@ func (hv History) Iterate(f func(eval.Value) bool) {
 }
 
 func (hv History) IndexOne(idx eval.Value) eval.Value {
+	hv.mutex.RLock()
+	defer hv.mutex.RUnlock()
+
 	slice, i, j := eval.ParseAndFixListIndex(eval.ToString(idx), hv.Len())
 	if slice {
 		ss := make([]eval.Value, j-i)
diff --git a/edit/history.go b/edit/history.go
index 3ac7f1c1..d0db786f 100644
--- a/edit/history.go
+++ b/edit/history.go
@@ -68,11 +68,13 @@ func (h *hist) jump(i int, line string) {
 
 func (ed *Editor) appendHistory(line string) {
 	if ed.store != nil {
+		ed.historyMutex.Lock()
 		go func() {
 			ed.store.Waits.Add(1)
 			// TODO(xiaq): Report possible error
 			ed.store.AddCmd(line)
 			ed.store.Waits.Done()
+			ed.historyMutex.Unlock()
 			Logger.Println("added cmd to store:", line)
 		}()
 	}
diff --git a/edit/module.go b/edit/module.go
index b71ea882..f7b580f3 100644
--- a/edit/module.go
+++ b/edit/module.go
@@ -40,7 +40,7 @@ func makeModule(ed *Editor) eval.Namespace {
 	ns["rprompt"] = ed.rps1
 	ns["rprompt-persistent"] = BoolExposer{&ed.rpromptPersistent}
 	ns["current-command"] = StringExposer{&ed.line}
-	ns["history"] = eval.NewRoVariable(History{ed.store})
+	ns["history"] = eval.NewRoVariable(History{&ed.historyMutex, ed.store})
 
 	ns["abbr"] = eval.NewRoVariable(eval.MapStringString(ed.abbreviations))