Problem: Diagnostic virtual lines are hardcoded with "scroll" for
virt_lines_overflow option.
Solution: Add a `overflow` option to `virtual_lines` config
to support "wrap", "scroll", "trunc", and "auto".
Problem:
Diagnostic highlight groups were applied by iterating and calling
`vim.hl.range` for each group individually. That resulted in multiple
extmarks with the same priority being created separately, which does not
allow `DiagnosticUnnecessary` and `DiagnosticDeprecated` with matching
options override `Diagnostic*` styling.
Solution:
Pass the list of hl-groups to `vim.hl.range` so they are applied
together in the correct order.
Problem:
`nvim_create_autocmd` is too verbose and its `callback` requires extra
"nesting".
Solution:
Introduce `nvim_on`. Start using it internally. Then we can get a feel
for how it should look before making it public.
Extract the diagnostic implementation from
runtime/lua/vim/diagnostic.lua into focused internal modules covering
config, display, float rendering, jump/list helpers, namespace and
storage management, severity/shared utilities, and statusline support.
Move the builtin handlers into runtime/lua/vim/diagnostic/handlers/ and
keep runtime/lua/vim/diagnostic.lua as the public facade that lazily
dispatches to the split modules. This preserves the external
vim.diagnostic API while making the implementation easier to navigate
and reason about.
AI-assisted: Codex
