Problem:
The magic globals `it`, `describe`, etc., are more trouble than they are
worth.
- Hooking into `after_each` requires `getfenv()` hacks.
- They confuse luals/emmylua, because the top-level `.luarc.json` isn't
merged with `test/.luarc.json` (apparently a luals limitation?)
- They totally defeat discoverability because the user just has to
"know" about the various magic symbols.
So they harm DX, which means they serve no purpose at all.
Solution:
- Expose the test API from `testutil`, so tests can call `t.it()`,
`t.describe()`, etc., in the conventional way.
- Drop `getfenv()` hacks.
- Drop the `setfenv()` injection in `load_chunk`.
- Drop `test/_meta.lua`.
Problem:
`vim.lsp.buf.format()` accepts ranges using nvim indexing, where an
end column of -1 means end of line. LSP ranges cannot use that,
which is confusing for things like range formatting.
Solution:
Resolve -1 end columns to the line length before converting the range to
LSP positions.
Problem:
The fromRanges field of the result of callHierarchy/outgoingCalls is
documented as being relative to the caller. Using
vim.lsp.buf.outgoing_calls() opened the qflist with an entry with the
callee's filename, but the caller's line number.
Solution:
Open the qflist with the callers file (the bufnr from the request),
rather than the callees (the uri from the resulting CallHierarchyItem)
Problem:
Cursor-position `vim.lsp.buf.code_action()` requests include all diagnostics on the current line, so unrelated same-line diagnostics affect the returned actions.
Solution:
Filter same-line diagnostics to the cursor position for cursor-position requests.
Problem:
`test/functional/plugin/lsp_spec.lua` had grown into a large catch-all file that mixed core LSP client lifecycle coverage, `vim.lsp.buf.*` behavior, and `vim.lsp.util.*` behavior in one place.
Solution:
Split the large tests into more focused test files without changing test coverage or intended behavior.
After this change, `lsp_spec.lua` is more focused on core LSP client/config/dynamic-registration behavior.
