MM-10833: send down computed channel props (#8953)

* MM-10833: send down computed channel props

This allows channel headers to reference channel mentions for a client
that doesn't already know about the channels in question.

We intentionally don't send down the props for the autocomplete and
search endpoints since they aren't used in that context, and would add
unnecessary overhead.

* update channel props on patch

* revert to treating channel purpose as plaintext

api4/channel.go

@@ -209,13 +209,20 @@ func patchChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if rchannel, err := c.App.PatchChannel(oldChannel, patch, c.Session.UserId); err != nil {
+	rchannel, err := c.App.PatchChannel(oldChannel, patch, c.Session.UserId)
+	if err != nil {
 		c.Err = err
 		return
-	} else {
-		c.LogAudit("")
-		w.Write([]byte(rchannel.ToJson()))
 	}
+
+	err = c.App.FillInChannelProps(rchannel)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	c.LogAudit("")
+	w.Write([]byte(rchannel.ToJson()))
 }
 
 func restoreChannel(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -361,6 +368,12 @@ func getChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	err = c.App.FillInChannelProps(channel)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
 	w.Write([]byte(channel.ToJson()))
 }
 
@@ -444,13 +457,19 @@ func getPublicChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Request
 		return
 	}
 
-	if channels, err := c.App.GetPublicChannelsForTeam(c.Params.TeamId, c.Params.Page*c.Params.PerPage, c.Params.PerPage); err != nil {
+	channels, err := c.App.GetPublicChannelsForTeam(c.Params.TeamId, c.Params.Page*c.Params.PerPage, c.Params.PerPage)
+	if err != nil {
 		c.Err = err
 		return
-	} else {
-		w.Write([]byte(channels.ToJson()))
+	}
+
+	err = c.App.FillInChannelsProps(channels)
+	if err != nil {
+		c.Err = err
 		return
 	}
+
+	w.Write([]byte(channels.ToJson()))
 }
 
 func getDeletedChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -464,13 +483,19 @@ func getDeletedChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Reques
 		return
 	}
 
-	if channels, err := c.App.GetDeletedChannels(c.Params.TeamId, c.Params.Page*c.Params.PerPage, c.Params.PerPage); err != nil {
+	channels, err := c.App.GetDeletedChannels(c.Params.TeamId, c.Params.Page*c.Params.PerPage, c.Params.PerPage)
+	if err != nil {
 		c.Err = err
 		return
-	} else {
-		w.Write([]byte(channels.ToJson()))
+	}
+
+	err = c.App.FillInChannelsProps(channels)
+	if err != nil {
+		c.Err = err
 		return
 	}
+
+	w.Write([]byte(channels.ToJson()))
 }
 
 func getPublicChannelsByIdsForTeam(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -497,12 +522,19 @@ func getPublicChannelsByIdsForTeam(c *Context, w http.ResponseWriter, r *http.Re
 		return
 	}
 
-	if channels, err := c.App.GetPublicChannelsByIdsForTeam(c.Params.TeamId, channelIds); err != nil {
+	channels, err := c.App.GetPublicChannelsByIdsForTeam(c.Params.TeamId, channelIds)
+	if err != nil {
 		c.Err = err
 		return
-	} else {
-		w.Write([]byte(channels.ToJson()))
 	}
+
+	err = c.App.FillInChannelsProps(channels)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	w.Write([]byte(channels.ToJson()))
 }
 
 func getChannelsForTeamForUser(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -521,15 +553,24 @@ func getChannelsForTeamForUser(c *Context, w http.ResponseWriter, r *http.Reques
 		return
 	}
 
-	if channels, err := c.App.GetChannelsForUser(c.Params.TeamId, c.Params.UserId); err != nil {
+	channels, err := c.App.GetChannelsForUser(c.Params.TeamId, c.Params.UserId)
+	if err != nil {
 		c.Err = err
 		return
-	} else if c.HandleEtag(channels.Etag(), "Get Channels", w, r) {
-		return
-	} else {
-		w.Header().Set(model.HEADER_ETAG_SERVER, channels.Etag())
-		w.Write([]byte(channels.ToJson()))
 	}
+
+	if c.HandleEtag(channels.Etag(), "Get Channels", w, r) {
+		return
+	}
+
+	err = c.App.FillInChannelsProps(channels)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	w.Header().Set(model.HEADER_ETAG_SERVER, channels.Etag())
+	w.Write([]byte(channels.ToJson()))
 }
 
 func autocompleteChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -545,12 +586,15 @@ func autocompleteChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Requ
 
 	name := r.URL.Query().Get("name")
 
-	if channels, err := c.App.AutocompleteChannels(c.Params.TeamId, name); err != nil {
+	channels, err := c.App.AutocompleteChannels(c.Params.TeamId, name)
+	if err != nil {
 		c.Err = err
 		return
-	} else {
-		w.Write([]byte(channels.ToJson()))
 	}
+
+	// Don't fill in channels props, since unused by client and potentially expensive.
+
+	w.Write([]byte(channels.ToJson()))
 }
 
 func searchChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -570,12 +614,15 @@ func searchChannelsForTeam(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if channels, err := c.App.SearchChannels(c.Params.TeamId, props.Term); err != nil {
+	channels, err := c.App.SearchChannels(c.Params.TeamId, props.Term)
+	if err != nil {
 		c.Err = err
 		return
-	} else {
-		w.Write([]byte(channels.ToJson()))
 	}
+
+	// Don't fill in channels props, since unused by client and potentially expensive.
+
+	w.Write([]byte(channels.ToJson()))
 }
 
 func deleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -638,6 +685,12 @@ func getChannelByName(c *Context, w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	err = c.App.FillInChannelProps(channel)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
 	w.Write([]byte(channel.ToJson()))
 }
 
@@ -660,6 +713,12 @@ func getChannelByNameForTeamName(c *Context, w http.ResponseWriter, r *http.Requ
 		return
 	}
 
+	err = c.App.FillInChannelProps(channel)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
 	w.Write([]byte(channel.ToJson()))
 }