Add option to enable processing on post update

plugin.json

@@ -19,6 +19,12 @@
         "display_name": "Enable administration with /autolink command",
         "type": "bool",
         "default": false
+      },
+      {
+        "key": "EnableOnUpdate",
+        "display_name": "Apply plugin to updated posts as well as new posts",
+        "type": "bool",
+        "default": false
       }
     ]
   }

server/config.go

@@ -12,6 +12,7 @@ import (
 // Config from config.json
 type Config struct {
 	EnableAdminCommand bool
+	EnableOnUpdate     bool
 	Links              []Link
 }
 
@@ -74,6 +75,7 @@ func (conf Config) ToConfig() map[string]interface{} {
 	}
 	return map[string]interface{}{
 		"EnableAdminCommand": conf.EnableAdminCommand,
+		"EnableOnUpdate":     conf.EnableOnUpdate,
 		"Links":              links,
 	}
 }

server/plugin.go

@@ -20,9 +20,7 @@ type Plugin struct {
 	confLock sync.RWMutex
 }
 
-// MessageWillBePosted is invoked when a message is posted by a user before it is committed
-// to the database.
-func (p *Plugin) MessageWillBePosted(c *plugin.Context, post *model.Post) (*model.Post, string) {
+func (p *Plugin) ProcessPost(c *plugin.Context, post *model.Post) (*model.Post, string) {
 	conf := p.getConfig()
 	postText := post.Message
 	offset := 0
@@ -98,3 +96,20 @@ func (p *Plugin) MessageWillBePosted(c *plugin.Context, post *model.Post) (*mode
 
 	return post, ""
 }
+
+// MessageWillBePosted is invoked when a message is posted by a user before it is committed
+// to the database.
+func (p *Plugin) MessageWillBePosted(c *plugin.Context, post *model.Post) (*model.Post, string) {
+	return p.ProcessPost(c, post)
+}
+
+// MessageWillBeUpdated is invoked when a message is updated by a user before it is committed
+// to the database.
+func (p *Plugin) MessageWillBeUpdated(c *plugin.Context, post *model.Post, _ *model.Post) (*model.Post, string) {
+	conf := p.getConfig()
+	if conf.EnableOnUpdate {
+		return p.ProcessPost(c, post)
+	} else {
+		return post, ""
+	}
+}

server/plugin_test.go

@@ -77,6 +77,7 @@ func TestSpecialCases(t *testing.T) {
 	})
 	validConfig := Config{
 		EnableAdminCommand: false,
+		EnableOnUpdate:     true,
 		Links:              links,
 	}
 
@@ -220,13 +221,54 @@ func TestSpecialCases(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.inputMessage, func(t *testing.T) {
-			post := &model.Post{
-				Message: tt.inputMessage,
+			{
+				// user creates a new post
+
+				post := &model.Post{
+					Message: tt.inputMessage,
+				}
+
+				rpost, _ := p.MessageWillBePosted(&plugin.Context{}, post)
+
+				assert.Equal(t, tt.expectedMessage, rpost.Message)
+			}
+			{
+				// user updates the modified post but with no changes
+
+				post := &model.Post{
+					Message: tt.expectedMessage,
+				}
+
+				rpost, _ := p.MessageWillBeUpdated(&plugin.Context{}, post, post)
+
+				assert.Equal(t, tt.expectedMessage, rpost.Message)
 			}
+			{
+				// user updates the modified post and sets it back to the original text
 
-			rpost, _ := p.MessageWillBePosted(&plugin.Context{}, post)
+				originalPost := &model.Post{
+					Message: tt.expectedMessage,
+				}
+				post := &model.Post{
+					Message: tt.inputMessage,
+				}
 
-			assert.Equal(t, tt.expectedMessage, rpost.Message)
+				rpost, _ := p.MessageWillBeUpdated(&plugin.Context{}, originalPost, post)
+
+				assert.Equal(t, tt.expectedMessage, rpost.Message)
+			}
+			{
+				// user updates an empty post to the original text
+
+				emptyPost := &model.Post{}
+				post := &model.Post{
+					Message: tt.inputMessage,
+				}
+
+				rpost, _ := p.MessageWillBeUpdated(&plugin.Context{}, post, emptyPost)
+
+				assert.Equal(t, tt.expectedMessage, rpost.Message)
+			}
 		})
 	}
 }