fix: avoid propagating empty context_lines

[Freyskeyd]

Description

This PR fixes an issue where sometime the ctx_lines used to define the height were empty, triggering an error about invalid height:

lua/treesitter-context/render.lua:51: 'height' key must be a positive Integer

The fix is checking if the context_lines are not empty, if it is, the close method is called.

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[lewis6991]

The block above should catch this. context_lines should be nil is context is.

[Freyskeyd]

I get this response from get_context as an example:

context_ranges: { { 74, 0, 73, -1 } }
context_lines: { {} }
context_lines (flatten): {}

After investigating a bit it seems that the trim_contexts is the problem:

print(vim.inspect(context_ranges), vim.inspect(context_lines))
trim_contexts(context_ranges, context_lines, trim, config.trim_scope == 'outer')
print(vim.inspect(context_ranges), vim.inspect(context_lines))

---

{ { 62, 0, 62, -1 }, { 64, 0, 64, -1 }, { 74, 0, 73, -1 } }  |  { { "impl TaskManager {" }, { "    pub fn new(" }, {} } 
-> trim
{ { 74, 0, 73, -1 } } { {} }

[Freyskeyd]

@lewis6991 After some tests I think that the problem rely in the cleaning of the contexts

[Freyskeyd]

Hey @lewis6991 !

Any chance to make this problem fix in some way? It is pretty annoying on a daily basis ahah.
I'm ready to make changes or update to this PR if needed !

[lewis6991]

I've done some changes recently is this still an issue? If so do you have a way to reproduce the problem?

[Freyskeyd]

@lewis6991 I'll update and let you know if I encounter the issue again, thanks !

[lewis6991]

I'll assume this isn't an issue any more. Let me know if it is.