Avoid pcall on vim.treesitter.language.add as it doesn't assert/error

[jship]

pcall-ing vim.treesitter.language.add would always return true as its first result value, as add uses the style of returning nil and an error message when it can't add the language rather than aborting via error or assert. This causes an issue when a Conjure user opens a Python buffer but doesn't have a Python treesitter parser installed. Conjure thinks they do have a parser installed and tries to start the stdio client. The user would see an error from Neovim's treesitter code like vim.schedule: No parser for language "python", and not the stdio client's intended log messages for this case (reproduced below) which made it difficult to identify that the error was originating from Conjure.

(error) The python client requires a python treesitter parser in order to function.
(error) See https://github.com/nvim-treesitter/nvim-treesitter
(error) for installation instructions.

The style of return nil plus error message is a change from the now-deprecated require_language functions that Conjure's add-language also wraps for backwards-compatiblity. The pcall was previously around the add-language wrapper call in the Python stdio client's start function. These changes move the choice to pcall or not into the add-language wrapper itself. This lets add skip a pcall while the deprecated require_language functions still get a pcall.

[russtoku]

It doesn't appear that the clause on L.196 would ever match because :require_language isn't a key in vim.treesitter.

[jship]

It no longer exists in more current versions of Neovim, but I preserved this case since the old version of the Conjure code was falling back to it too. Here's the 2020 Neovim commit where it was introduced and here's the (also 2020) commit where it was moved from top-level vim.treesitter to be under vim.treesitter.language. For completeness' sake, here's the 2024 commit where it was renamed from require_language to add.

[Olical]

Nice, I would also point out that our minimum version is v0.10 so we should try to be backwards compatible to there but if someone's on <0.10 Conjure will error anyway. I didn't look into the version numbers these changes correspond to but I'm okay with this backwards compatibility regardless, just thought I'd mention the version threshold anyway.

I also didn't know Fennel case statements could be used like this, I really like it!

[russtoku]

Good catch!

Your changes make it clear what a user needs to do if they don't have a Tree-sitter parser for Python.

Without your changes, the user has to suffer these error messages:

• When first editing a Python source file.

Error executing vim.schedule lua callback: ...5/share/nvim/runtime/lua/vim/treesitter/languagetree.lua:125: No
 parser for language "python"
stack traceback:
        [builtin#19]: at 0x0104f597c4

• When trying to evaluate a line of Python code from a buffer.

E5108: Error executing lua: Vim:Error executing Lua callback: ...5/share/nvim/runtime/lua/vim/treesitter/langu
agetree.lua:125: No parser for language "python"
stack traceback:
        [C]: in function 'assert'
        ...5/share/nvim/runtime/lua/vim/treesitter/languagetree.lua:125: in function 'get_string_parser'
        ...lugins/start/conjure/lua/conjure/client/python/stdio.lua:76: in function 'str-is-python-expr?'
        ...lugins/start/conjure/lua/conjure/client/python/stdio.lua:86: in function 'prep_code'
        ...lugins/start/conjure/lua/conjure/client/python/stdio.lua:157: in function <...lugins/start/conjure/
lua/conjure/client/python/stdio.lua:146>
        ...vim/site/pack/plugins/start/conjure/lua/conjure/eval.lua:150: in function <...vim/site/pack/plugins
/start/conjure/lua/conjure/eval.lua:138>
        [C]: at 0x0102ad13d4
stack traceback:
        [C]: at 0x0102ad13d4

[Olical]

Nice, I would also point out that our minimum version is v0.10 so we should try to be backwards compatible to there but if someone's on <0.10 Conjure will error anyway. I didn't look into the version numbers these changes correspond to but I'm okay with this backwards compatibility regardless, just thought I'd mention the version threshold anyway.

I also didn't know Fennel case statements could be used like this, I really like it!