Mattermost-server: Allow uploading 10 files per post

[mattermod]

Currently we limit file uploads per post to 5. This ticket is to increase the limit to 10 and update any associated help text.

With new file upload features like a photo picker on mobile we will want to increase the files per post that can be shared for better UX.

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JIRA: https://mattermost.atlassian.net/browse/MM-27312

[DigasNikas]

Greetings.
Can I move forward with this one?

[esethna]

@DigasNikas you got it, thanks!

[DigasNikas]

Greetings, after a while I’ve found what needed to change, but I must say I’m a bit confused with the logic. Any chance anyone here can clarify the idea behind?

I would argue it looks clearer to have POST_MAX_FILES = 5 instead of POST_FILEIDS_MAX_RUNES = 150 if we want to limit the number of files to 5.

And then:
if len(o.FileIds) > POST_MAX_FILES {
Instead of
if utf8.RuneCountInString(ArrayToJson(o.FileIds)) > POST_FILEIDS_MAX_RUNES {

I must say 1 month ago when I first got my eyes into this logic I quickly discarded it. I'd have bet it was trying to achieve something extra :smile:

[hanzei]

@streamer45 @hmhealey Can you help with the question above? :point_up:

[hmhealey]

Yeah, I can explain why it's written that way. We have a bit of an odd setup where there's a two-way reference between the Post and FileInfo tables in the database. Each FileInfo has a PostId, and each Post has an array of FileIds that are written into the database as a json array stored in a string. All of our IDs are 26 characters long normally, so 5 file IDs plus the rest of the JSON is a little under 150 characters long in the database.

I like the idea of making it clearer by adding POST_MAX_FILES. I'll also add this as a comment on the PR, but since we still need to confirm that the FileIds value doesn't overflow the column, I think it might be best to have two constants and just check both.

[DigasNikas]

@hmhealey thanks for the detailed explanation!
Followed your suggestion.

model.post.is_valid.file_ids.app_error is now used for POST_MAX_FILES and POST_FILEIDS_MAX_RUNES checks. Probably it would be nice to eventually split this error in two.

[hmhealey]

FYI, I created a separate Jira ticket to track adding this on mobile to ensure that gets done as well.

https://mattermost.atlassian.net/browse/MM-31257