Prefer ale_root option when detecting roots

[w0rp]

Summary

• add ale#linter#GetRoot and use it when starting LSP linters
• use ale_root first in ale#python#FindProjectRoot
• update docs to describe the new root lookup behaviour
• adjust tests and add new test for python root option

Testing

• ./run-tests --fast (fails: docker not found)

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https://chatgpt.com/codex/tasks/task_b_685c4b409780832aaeb2154798173c38

[Copilot]

Pull Request Overview

This PR introduces a unified ale#linter#GetRoot function to prefer the g:ale_root/b:ale_root settings when detecting project roots, replaces legacy root-detection calls with it, and updates documentation and tests accordingly.

• Added ale#linter#GetRoot and wired it into LSP and Python linters
• Updated tests to cover the new root-lookup priority
• Revised documentation (ale.txt, ale-python.txt) to describe the new behavior

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
autoload/ale/linter.vim	New GetRoot function that handles ale_root vars
autoload/ale/python.vim	Python root lookup now uses GetRoot
autoload/ale/lsp_linter.vim	Removed old FindProjectRoot, now calls GetRoot
autoload/ale/assert.vim	Assertion helper updated to use GetRoot
ale_linters/python/pyright.vim	Use GetRoot instead of LSP-specific finder
ale_linters/python/pylsp.vim	Ditto for pylsp
test/test_python_root_option.vader	New tests for buffer/global ale_root behaviors
test/test_linter_defintion_processing.vader	Updated tests to assert GetRoot is used
doc/ale.txt	Documentation of g:ale_root updated
doc/ale-python.txt	Added note on ale_root shortcut for Python

[Copilot]

GetRoot currently returns an empty string by default when no root is found, which drops the fallback to a linter's existing project_root_callback. Consider invoking a:linter.project_root_callback (via ale#util#GetFunction) when present to maintain the original behavior for linters that define callbacks.

Suggested change

	if has_key(a:linter, 'project_root_callback')
	let l:Callback = ale#util#GetFunction(a:linter.project_root_callback)
	if type(l:Callback) is v:t_func
	return l:Callback(a:buffer)
	endif
	endif

[rymdbar]

Problems, as well as confusion, with getting the correct project root happens often enough for this to warrant both a technical change such as the one in this pull-request and some updates to the documentation.

I might be confused myself and mixing contexts, but figure it's likely a good idea to add this quote of myself from #3481 here:

Adding a sentence or section to the documentation about the need for the for a project root to be found would likely be a good idea too. This might be a common theme applying to the documentation for most language servers.

Expecting everyone to have read :help ale-options.root and realise it is what is needed is probably unrealistic.

My mind is a bit fuzzy and my notes aren't making it crystal clear, but I think once the project roots are discovered the same way for all language servers, what needs to be done is to go through documentation for them all and make sure it mentions the requirement for a root to be found and the ability to hard code the root if desired.