Syntax error: KeyError) key :color not found in: nil (but app works on a different machine)

Questions / Help
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1

I have three instances of an app on different machines that I have updates a LiveView page to.

These three machines are Local Machine, a Dev Machine and Live Machine.

The app on Local Machine is a clone of the Phoenix App on Live Machine. I literally copied it over before working on it.

The live view page I edited is named: page_live.ex
On Local Machine I edited page_live.ex and then copied it to Dev Machine in the same directory it was in on the Live Machine.

The change worked and rendered as expected and Dev Machine updated accordingly. I thought "hey , I’ll update the Live Machine " now.

On my Live machine when I upload the file I get this syntax error:

KeyError at GET /
key :color not found in: nil. If you are using the dot syntax, such as map.field, make sure the left-hand side of the dot is a map
# KeyError at GET /

Exception:

    ** (KeyError) key :color not found in: nil. If you are using the dot syntax, such as map.field, make sure the left-hand side of the dot is a map
        (app 0.1.0) lib/app_web/live/page_live.ex:506: anonymous fn/4 in AppWeb.PageLive.render/1
        (elixir 1.14.3) lib/enum.ex:2468: Enum."-reduce/3-lists^foldl/2-0-"/3
        (app 0.1.0) lib/app_web/live/page_live.ex:501: anonymous fn/2 in AppWeb.PageLive.render/1

All the dependencies I see between systems are the same. The Dev Machine and the Live Machine have the same version of Elixir.

What can be wrong?

I have not run phx.deps.get yet as I am waiting for my server admin buddy to make a backup first but I am unsure how that would fix this as I did not need to do it with the Dev Machine

Thank you.

EDIT

I just grabbed all the code off Live Machine and re-copied it to another directory on my Local Machine.

Runing it gave me some non related errors so I deleted the .build directory and did mix phx.digest

I manually copied over the new page_live.ex file and it works with no error.

I am not sure why copying it over to directly to Live Machine doesn’t work the same.

Like I said, maybe it will be solved by a rebuild but it’s still a weird error.

2

This error message is the symptom - you’ve got code that does some_variable.color when some_variable is bound to nil.

The cause is whatever’s putting nil in some_variable, when you’re expecting a map to be there.

3

Yes that is what the error is saying but it doesn’t help me diagnose the problem when viewed in the context of the post. One thing I left out is that my Local Machine instance was a clone of my Live Machine instance. I’ll add that info to the initial post.

EDIT
@al2o3cr I am assuming the structure of data for all databases were exactly the same. I think that was the wrong assumption.

4

The code can be the same but if the app is fetching data from somewhere then that data can differ. The binding you are expecting to be a map, what is its value coming from?

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5

I understand they’re running the same code - my point is that something in lib/app_web/live/page_live.ex is getting different data at runtime.

Showing that code would be useful to diagnose further.

3 Likes
6

Yeah I see. I just made an edit above

I am assuming the structure of data for all databases were exactly the same. I think that was the wrong assumption. :frowning:

7

Even if the structure of the tables were the same, having different rows of data in the database can cause nil values to be returned

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