feat: Markdown / custom processing support

[Picalines]

Hi, great plugin!

It'd be nice if this plugin could wrap TS types in a markdown symbols, like:

Type

```ts
  {
    field: number
  }

Is not assignable to number

So other plugins like `noice.nvim` could highlight the diagnostic popup using treesitter for example

I think there're two ways to implement it:
1. Direct option like `format = 'markdown'`, while the current behaviour is `format = 'plain'` or something
2. Two generic functions for formatting blocks and inlines, line:
```lua
format = {
  inline = function (text) return '`' .. text .. '`',
  block = function (text)
    return '```ts\n' .. text .. '\n```'
  return
}

Second approach is more difficult, because we'd need to choose what data to pass in function parameters (is text already prettified? How to handle nested indentation?)

[davidosomething]

updated with:

{
    "davidosomething/format-ts-errors.nvim",
    config = function()
      require("format-ts-errors").setup({
        add_markdown = true, -- wrap output with markdown ```ts ``` markers
        start_indent_level = 0, -- initial indent
      })
    end,
}

lmk if that works

[Picalines]

It seems like the TS blocks are not indented now

Not entirely sure what's happening, i'll share a better screenshot when i found one

[davidosomething]

if you could share the file as well it would help

[Picalines]

Here's a short example:

type Obj1 = { field: number }
type Obj2 = { field: string }
const x: Obj1 = {field: 123}
const y: Obj2 = x

Current output is:

Type

```ts
Obj1

is not assignable to type

Obj2

Types of property 'field' are incompatible. Type

number

is not assignable to type

string

(2322)

The ` (2322)` is part of [neovim configuration](https://neovim.io/doc/user/diagnostic.html#vim.diagnostic.Opts.Float), it can be fixed on the user side

[davidosomething]

are you using start_indent_level = 0, -- initial indent ? The default before this change was 1

[Picalines]

are you using start_indent_level = 0, -- initial indent ? The default before this change was 1

Yes, i'm using start_indent_level = 0

[davidosomething]

remove that line or change it to start_indent_level = 1 to bring back initial indent

[Picalines]

remove that line or change it to start_indent_level = 1 to bring back initial indent

It produces the same result for the example i posted above

[davidosomething]

i am unable to replicate, can you post a minimal config? here's what i see with start_indent_level = 1

[Picalines]

Sorry, it turn's out that render-markdown plugin removes the indentation in code blocks

That's my output without the plugin:

Type

```ts
  Obj1

is not assignable to type

  Obj2

Types of property 'field' are incompatible. Type

  number

is not assignable to type

  string

@davidosomething
Is the `Types of property 'field' are incompatible` indented correctly? You can close the issue if that's intended

---

If anyone stumbles across this, you can turn off render-markdown's `indent` feature to keep the highlighting

Here's how i've configured neovim to render "Diagnostics" as markdown:
```lua
local builtin_open_float = vim.diagnostic.open_float

---@diagnostic disable-next-line: duplicate-set-field
vim.diagnostic.open_float = function(...)
    local bufnr, winid = builtin_open_float(...)

    if bufnr and winid then
        vim.api.nvim_set_option_value('filetype', 'markdown', { buf = bufnr })
    end

    return bufnr, winid
end

And here's how to tell neovim not to apply DiagnosticError highlight to the whole popup:

vim.diagnostic.config {
    signs = {
        -- text & numhl tables
    },

    float = {
        -- NOTE: format can't return the highlight, so we use prefix & suffix without it
        format = function() return '' end,

        prefix = function(report)
            local signs = vim.diagnostic.config().signs or {}
            local icon = signs.text[report.severity]
            return icon .. ' ', signs.numhl[report.severity]
        end,

        suffix = function(report)
            local hl = 'Normal'
            local message = vim.trim(report.user_data.lsp.message)

            if string.find(message, '\n') then
                return string.format('%s\n^ (%s)', message, report.code), hl
            end

            return string.format('%s (%s)', message, report.code), hl
        end,
    },
}

[davidosomething]

Is the Types of property 'field' are incompatible indented correctly? You can close the issue if that's intended

Yea, it comes newline+indented from typescript server.

It's possible to change the output of that as well using some regex to strip the extra indent, but the messaging changes between typescript versions so I'll leave it as an exercise to the user ;P

Thanks for using and following up on the issue!