Quick-fix for Edit'Set* cases when old Text value is empty

[babhishek21]

Quick Fix to issue #96.

• Currently, when old Text type value is empty, the descriptive text uses the word "added" instead of "changed". Other than that, the table column for the empty old value still exists. (See image below for example) Let me know if empty value columns require removal. That will require some more ninja chops. :hocho:
• Only some of the cases matching Edit'Set* have been modified. The ones which have not been touched are those which either have default old values which are not empty or null; or have a default enumerated value assigned to them (system-defined or Nothing), at the time of creation.

I am an absolute noob when it comes to Haskell.

• I hope my use of the if-then-else construct was justified (it seems to get the desired effect).
• When I needed to check if a Data.Text type object was empty, I referred to https://github.com/aelve/guide/blob/master/lib/View.hs#L62-L64 and only oldValue == T.empty or (T.null oldValue) seemed to work. I used the latter. (I don't fully understand why oldValue == Text.empty or (Text.null oldValue) don't work. I'll leave that as is.)

[neongreen]

I hope my use of the if-then-else construct was justified

Yep.

I don't fully understand why oldValue == Text.empty or (Text.null oldValue) don't work

Text.null doesn't work because of how Haskell import syntax works. In T.null, T is the module alias and null is the name of the function. Now:

• When Data.Text is imported like import qualified Data.Text as T, it makes T refer to Data.Text.
• If Data.Text was imported like import Data.Text as T, it'd make null available both as null and as T.null. People don't usually import Data.Text like that because lots of names there clash with ones in Prelude.
• If Data.Text was imported plainly like import Data.Text, it'd only make Data.Text.null available as null and it'd be impossible to call because it clashes with Prelude.null.

(By the way, you don't need parens around (T.null oldNotes) because if is a keyword, not a function, and so Haskell can figure out unambiguously that T.null oldNotes is the condition here.)

oldValue == T.empty

T.null oldValue is the preferred version. Generally in Haskell you use pattern-matching, case or predicates like null and isNothing when possible, though foo == "blah" is still more acceptable than foo == "" – this has to do with the fact that when you use foo == [] on lists in general, it works in less cases than null foo (because e.g. you can't compare an [Int -> Int] list with anything but you can still check whether it's empty or not). There are also other arguments here: http://stackoverflow.com/questions/3853922/null-instead-of.

Other than that, the table column for the empty old value still exists.

Can you fix this as well? It's not hard, you only need to conditionally execute the code that adds the table cell – e.g.

unless (T.null oldEcosystem) $ 
  td_ $ blockquote_ $ toHtml (toMarkdownBlock oldEcosystem)

[neongreen]

(Well, and check that CSS doesn't get broken when there's only one cell.)

[babhishek21]

Other than that, the table column for the empty old value still exists.

Can you fix this as well?

Done. :smile:

(Well, and check that CSS doesn't get broken when there's only one cell.)

The CSS did not break. In fact it looks the same as the case when you add a pro or a con. This is what it looks like: