Absolute paths in error messages for missing arguments

[benjamingeer]

Given a Fennel program like this:

(λ foo [bar] (print bar))
(foo :bar)

Nfnl compiles the code to produce this Lua program:

-- [nfnl] test.fnl
local function foo(bar)
  if (nil == bar) then
    _G.error("Missing argument bar on /home/ben/test/test.fnl:1", 2)
  else
  end
  return print(bar)
end
return foo("bar")

If I understand correctly, the absolute path is there because of fecf731. The problem is that if I commit this Lua file to a git repository, and someone else clones the repository, the error message will probably be incorrect on their machine. Even on my machine, if I move the Lua file to some other directory (e.g. /usr/local/bin), the error message will be incorrect.

If I compile the file manually with fennel --compile test.fnl > test.lua, I get:

local function foo(bar)
  if (nil == bar) then
    _G.error("Missing argument bar on test.fnl:1", 2)
  else
  end
  return print(bar)
end
return foo("bar")

Could Nfnl please do this instead?

[Olical]

I think these paths are coming from the Fennel compiler itself, I'll have to have a look and see if that's hard coded inside it or if there's an option I can provide to it on your behalf. The last resort would be post-processing the Lua files after they're compiled but I'd like to avoid that if possible.

[Olical]

Let me know what you think, I have a feeling I've fixed it, I just hope there's no adverse side effects. I started adding absolute paths everywhere because it was the only way to keep Windows happy I think 🤔

[NoahTheDuke]

I actually opened a fennel bug ticket about this last month and then forgot to follow up here lol. thanks for handling this.

[benjamingeer]

@Olical thanks for the fix! Now the error message contains a relative path from the project root. This is OK if someone just clones the project, but would still be incorrect if I installed the Lua script somewhere in my PATH, outside the project. I'd prefer just to have the filename in the error message, but if you'd rather keep it this way, that's OK too, I can work around it by using a Makefile to compile everything that might be installed elsewhere.

[Olical]

So the issue is that the Fennel compiler compiles these paths directly into the output Lua, so we'd need to compile each Lua file on each run to handle any potential moves of that file over time. If the path were dynamically calculated then we could print the full path but that requires a Fennel compiler change I'm afraid. For now the best I can offer is relative to project root since the output Lua is static and the paths get written into the compiled output.

[benjamingeer]

Understood, let's leave it like that, it's OK with me. And thank you!