Lua: "reaper.xyz is unknown" terminates the script with pcall

[cfillion]

counter = 0

function loop()
  counter = counter + 1
  reaper.ShowConsoleMsg(string.format("loop %d\n", counter))

  pcall(function()
    gfx.hello_world = 42
  end)

  if counter < 50 then
    reaper.defer(loop)
  end
end

loop()

Result:

When clicking on the "Continue" button in the error dialog, the loop() function is ran only twice, instead of 50 times:



Expected:

No error dialog at all (because of pcall), or a least it should not abort the script when clicking on the Continue button.

[X-Raym]

Here is a workarround (with SWS extension check)
ReaScripts-Templates/X-Raym_Check if SWS is installed and download if not.lua at master · ReaTeam/ReaScripts-Templates

The trick is to loop in reaper function table and store existing key (aka function names) in a table, and check if an extension function (no matter which one) exist in this table or not.
It doesn't return REAPER error if it doesn't exist.

EDIT: code snippet updated with new method, base don NammedCommand

[cfillion]

It's not a perfect workaround though. pairs(reaper) seems to be giving "ghost" functions, such as:

• 'reaper.ov_info' is unknown
• 'reaper.ov_pcm_total' is unknown
• 'reaper.wave__createMetadataSource' is unknown

They are functions (type(v) == 'function'), but when called they throw the dreaded non-catchable "is unknown" error.

for k,v in pairs(reaper) do
  reaper.ShowConsoleMsg(string.format("%s is a %s\n", k, type(v)))
end

-- this prints "function"
reaper.ShowConsoleMsg(string.format("%s\n", type(reaper.ov_read_float)))

-- but this crashes the script with the fatal "is unknown" error
reaper.ov_read_float()

[X-Raym]

I update the code snippet with a Workaround by Heda that works with NamedCommand instead of looping reaper table

way more efficient and reliable.

[cfillion]

@X-Raym Nice trick for checking SWS's presence.

Summary of the bugs/annoyances so far:

1. "reaper.xyz is unknown" error always stop the script execution when using reaper.defer() and clicking on the "Continue" button when the IDE is closed
2. "reaper.xyz is unknown" error cannot be caught by lua's pcall() unlike other lua/reascript errors
3. reaper['inexistant'] behavior is inconsistent with lua table behavior: it throws an error instead of returning nil EDIT: This one is fixed in REAPER 5.23pre1!
4. pairs(reaper) gives ghost (uncallable and undocumented) functions EDIT: Fixed in v5.23pre2!

(These all affect my interactive reascript script, I guess it's kind of an edge case...)

[schwa]

This is all fairly complicated under the hood. However, it should be easy for us to add an API function API_exists("function_name"), does that get you where you want to be?

[schwa]

On second thought, we'll do both. The next build will add APIExists("function_name"), and also treat reaper.* as a generic table with respect to getting and setting elements. So reaper.somefunction will be nil if somefunction() is not defined in the particular version of REAPER that is running the script. As a side effect you'll be able to set reaper.whatever="foo" and that will work too, though that's somewhat pointless.

[cfillion]

Awesome, thank you! Will gfx also be changed? Currently it has the same "is unknown" behavior and non-function indexes – x, w, mouse_cap etc – are not listed by pairs(gfx). EDIT: it is

[Flaneurette]

Originally Posted by schwa

On second thought, we'll do both. The next build will add APIExists("function_name"), and also treat reaper.* as a generic table with respect to getting and setting elements. So reaper.somefunction will be nil if somefunction() is not defined in the particular version of REAPER that is running the script. As a side effect you'll be able to set reaper.whatever="foo" and that will work too, though that's somewhat pointless.

Can it enumerate SWS functions as well?

[cfillion]

Originally Posted by Flaneurette

Can it enumerate SWS functions as well?

Yes, extension functions too.

[Flaneurette]

Originally Posted by cfillion

Yes, extension functions too.

Tried to query CF_GetSWSVersion and it gave back: 0.

[cfillion]

With the latest SWS (2.12.1)? It works here:

[Flaneurette]

Originally Posted by cfillion

With the latest SWS (2.12.1)? It works here:

Yes, it works now. Forgot to add the function as string.

RPR_ShowConsoleMsg(RPR_APIExists("CF_GetSWSVersion"))

instead of:

RPR_ShowConsoleMsg(RPR_APIExists(CF_GetSWSVersion))

Last one gave zero.