feat: add support for rendering text with props

Introduce the ability to render text with attached text properties.
Renderers may now also return list of dictionaries where each line of
text can include text properties for additional text styling
capabilities. This change is backwards compatible with existing
renderers; they will continue to work as before. These features,
however, are not supported in Neovim.

The semantics of this feature was inspired by popup_create(), which can
accept a list of dictionaries with a 'text' and 'props' key.

Author: brandon1024

autoload/fern.vim

@@ -36,6 +36,7 @@ call s:Config.config(expand('<sfile>:p'), {
       \ 'default_exclude': '',
       \ 'renderer': 'default',
       \ 'renderers': {},
+      \ 'enable_textprop_support': 0,
       \ 'comparator': 'default',
       \ 'comparators': {},
       \ 'drawer_width': 30,

autoload/fern/internal/buffer.vim

@@ -5,14 +5,40 @@ function! fern#internal#buffer#replace(bufnr, content) abort
   let modifiable_saved = getbufvar(a:bufnr, '&modifiable')
   try
     call setbufvar(a:bufnr, '&modifiable', 1)
-    call setbufline(a:bufnr, 1, a:content)
-    call deletebufline(a:bufnr, len(a:content) + 1, '$')
+
+    if g:fern#enable_textprop_support
+      call s:replace_buffer_content(a:bufnr, a:content)
+    else
+      call setbufline(a:bufnr, 1, a:content)
+      call deletebufline(a:bufnr, len(a:content) + 1, '$')
+    endif
   finally
     call setbufvar(a:bufnr, '&modifiable', modifiable_saved)
     call setbufvar(a:bufnr, '&modified', modified_saved)
   endtry
 endfunction
 
+" Replace buffer content with lines of text with (optional) text properties.
+function! s:replace_buffer_content(bufnr, content) abort
+  for lnum in range(len(a:content))
+    let line = a:content[lnum]
+    let [text, props] = type(line) is# v:t_dict
+      \ ? [line.text, get(line, 'props', [])]
+      \ : [line, []]
+
+    call setbufline(a:bufnr, lnum + 1, text)
+
+    if exists('*prop_add')
+      for prop in props
+        let prop.bufnr = a:bufnr
+        call prop_add(lnum + 1, prop.col, prop)
+      endfor
+    endif
+  endfor
+
+  call deletebufline(a:bufnr, len(a:content) + 1, '$')
+endfunction
+
 function! fern#internal#buffer#open(bufname, ...) abort
   let options = extend({
         \ 'opener': 'edit',

autoload/fern/internal/drawer/hover_popup.vim

@@ -74,7 +74,7 @@ function! s:show() abort
     call setbufline('%', 1, line)
     call helper.fern.renderer.syntax()
     call helper.fern.renderer.highlight()
-    syntax clear FernRoot
+    syntax clear FernRootSymbol
     syntax clear FernRootText
 
     setlocal nowrap cursorline noswapfile nobuflisted buftype=nofile bufhidden=hide

doc/fern-develop.txt

@@ -558,7 +558,15 @@ nodes as a tree.
 
 					*fern-develop-renderer.render()*
 .render({nodes})
-	Return a promise which is resolved to a list of |String|.
+	Return a promise which is resolved to:
+
+	  a list of |String|, or
+	  if |g:fern#enable_textprop_support| is 1, a list of |Dictionary|
+		with the following entries:
+	    text  |String| with the text to display.
+	    props A list of text properties (|Dictionary|). Optional. Not supported
+	          for Neovim. Each entry is a dictionary, like the third argument
+	          of |prop_add()|, but specifying a column with a "col" entry.
 
 	Change (v1.6.0):~
 	Second argument ({marks}) has removed.

doc/fern.txt

@@ -523,6 +523,11 @@ VARIABLE						*fern-variable*
 	is a key of |g:fern#renderers|.
 	Default: "default"
 
+*g:fern#enable_textprop_support*
+	If set to 1, renderers may return lines of text with text properties.
+	May incur slight performance penalty. See |fern-develop-renderer|.
+	Default: 0
+
 *g:fern#comparator*
 	A |String| name of comparator used to sort tree items. Allowed value
 	is a key of |g:fern#comparators|.

test/fern/internal/buffer.vimspec

@@ -5,6 +5,16 @@ Describe fern#internal#buffer
 
   Before
     %bwipeout!
+    if !has('nvim')
+      call prop_type_add('test_prop', { 'highlight': 'Question' })
+    endif
+  End
+
+  After
+    let g:fern#enable_textprop_support = 0
+    if !has('nvim')
+      call prop_type_delete('test_prop')
+    endif
   End
 
   Describe #replace()
@@ -115,6 +125,45 @@ Describe fern#internal#buffer
             \])
       Assert Equals(getbufvar(bufnr, '&modified'), 1)
     End
+
+    It should replace buffer content with text and properties
+      if has('nvim')
+        Assert Skip('text properties are only supported in vim')
+      endif
+
+      let g:fern#enable_textprop_support = 1
+
+      let bufnr = bufnr('%')
+      call setline(1, [
+            \ "Hello",
+            \ "Darkness",
+            \ "My",
+            \ "Old",
+            \ "Friend",
+            \])
+      new
+      call fern#internal#buffer#replace(bufnr, [
+            \ { 'text': 'Empty Props', 'props': [] },
+            \ { 'text': 'Undefined Props' },
+            \ { 'text': 'With Properties!', 'props':
+            \   [{ 'col': 1, 'length': 4, 'type': 'test_prop' }]
+            \ },
+            \])
+      Assert Equals(getbufline(bufnr, 1, '$'), [
+            \ "Empty Props",
+            \ "Undefined Props",
+            \ "With Properties!",
+            \])
+
+      Assert True(empty(prop_list(1, { 'bufnr': bufnr })))
+      Assert True(empty(prop_list(2, { 'bufnr': bufnr })))
+
+      let result_props = prop_list(3, { 'bufnr': bufnr })
+      Assert Equal(len(result_props), 1)
+      Assert Equal(result_props[0].col, 1)
+      Assert Equal(result_props[0].length, 4)
+      Assert Equal(result_props[0].type, 'test_prop')
+    End
   End
 
   Describe #open()