feat(session_formatter): add selected text to format isolated part

The order of the context has been changed in order to have selection
before the current file

The seperator has been changed to '----' it was causing the user part to
not be formatted by render-markdown

Author: sudo-tee

lua/opencode/context.lua

@@ -327,6 +327,10 @@ function M.format_message(prompt, opts)
     end
   end
 
+  for _, sel in ipairs(context.selections or {}) do
+    table.insert(parts, format_selection_part(sel))
+  end
+
   for _, agent in ipairs(context.mentioned_subagents or {}) do
     table.insert(parts, format_subagents_part(agent, prompt))
   end
@@ -335,10 +339,6 @@ function M.format_message(prompt, opts)
     table.insert(parts, format_file_part(context.current_file.path))
   end
 
-  for _, sel in ipairs(context.selections or {}) do
-    table.insert(parts, format_selection_part(sel))
-  end
-
   if context.linter_errors then
     table.insert(parts, format_diagnostics_part(context.linter_errors))
   end
@@ -350,10 +350,10 @@ function M.format_message(prompt, opts)
   return parts
 end
 
----@param part OpencodeMessagePart
+---@param text string
 ---@param context_type string|nil
-local function decode_json_context(part, context_type)
-  local ok, result = pcall(vim.json.decode, part.text)
+function M.decode_json_context(text, context_type)
+  local ok, result = pcall(vim.json.decode, text)
   if not ok or (context_type and result.context_type ~= context_type) then
     return nil
   end
@@ -371,7 +371,7 @@ function M.extract_from_opencode_message(message)
       ctx.prompt = ctx.prompt or part.text or ''
     end,
     text_context = function(part)
-      local json = decode_json_context(part, 'selection')
+      local json = M.decode_json_context(part.text, 'selection')
       ctx.selected_text = json and json.content or ctx.selected_text
     end,
     file = function(part)

lua/opencode/ui/session_formatter.lua

@@ -14,7 +14,7 @@ local M = {
 }
 
 M.separator = {
-  '---',
+  '----',
   '',
 }
 
@@ -418,6 +418,7 @@ function M._format_user_message(text, message)
   M.output:add_lines(vim.split(context.prompt, '\n'))
 
   if context.selected_text then
+    M.output:add_empty_line()
     M.output:add_lines(vim.split(context.selected_text, '\n'))
   end
 
@@ -431,6 +432,22 @@ function M._format_user_message(text, message)
   M._add_vertical_border(start_line, end_line, 'OpencodeMessageRoleUser', -3)
 end
 
+---@param part MessagePart
+function M._format_selection_context(part)
+  local json = context_module.decode_json_context(part.text, 'selection')
+  if not json then
+    return
+  end
+  local start_line = M.output:get_line_count()
+  M.output:add_empty_line()
+  M.output:add_lines(vim.split(json.content, '\n'))
+  M.output:add_empty_line()
+
+  local end_line = M.output:get_line_count()
+
+  M._add_vertical_border(start_line, end_line, 'OpencodeMessageRoleUser', -3)
+end
+
 ---Format and display the file path in the context
 ---@param path string|nil File path
 function M._format_context_file(path)
@@ -747,6 +764,8 @@ function M.format_part_isolated(part, message_info)
     if message_info.role == 'user' and part.synthetic ~= true then
       M._format_user_message(vim.trim(part.text), message_info.message)
       content_added = true
+    elseif part.synthetic == true and message_info.role == 'user' then
+      M._format_selection_context(part)
     elseif message_info.role == 'assistant' then
       M._format_assistant_message(vim.trim(part.text))
       content_added = true