fix(context): multiple file references in diagnostics context, and improve format (#67)

Co-authored-by: Nick van Dyke <nickjvandyke15@gmail.com>

Author: chriswritescode-dev

lua/opencode/context.lua

@@ -171,20 +171,20 @@ end
 ---e.g. `@opencode.lua L21:C10-L65:C11`
 ---@param args { buf?: integer, path?: string, start_line?: integer, start_col?: integer, end_line?: integer, end_col?: integer }
 function Context.format(args)
-  assert(args.buf or args.path, "Must provide either `buf` or `path`")
-  if args.buf and not is_buf_valid(args.buf) then
-    return nil
+  local result = ""
+  if (args.buf and is_buf_valid(args.buf)) or args.path then
+    local rel_path = vim.fn.fnamemodify(args.path or vim.api.nvim_buf_get_name(args.buf), ":.")
+    -- Must be preceeded by @ and followed by space for `opencode` to parse as a file reference
+    result = "@" .. rel_path .. " "
   end
-  local rel_path = vim.fn.fnamemodify(args.path or vim.api.nvim_buf_get_name(args.buf), ":.")
-  local result = "@" .. rel_path
   if args.start_line and args.end_line and args.start_line > args.end_line then
     args.start_line, args.end_line = args.end_line, args.start_line
     if args.start_col and args.end_col then
       args.start_col, args.end_col = args.end_col, args.start_col
     end
   end
   if args.start_line then
-    result = result .. string.format(" L%d", args.start_line)
+    result = result .. string.format("L%d", args.start_line)
     if args.start_col then
       result = result .. string.format(":C%d", args.start_col)
     end
@@ -281,29 +281,30 @@ function Context:diagnostics()
   if #diagnostics == 0 then
     return nil
   end
+
+  local file_ref = Context.format({ buf = self.buf })
+
   local diagnostic_strings = {}
   for _, diagnostic in ipairs(diagnostics) do
+    local location = Context.format({
+      start_line = diagnostic.lnum + 1,
+      start_col = diagnostic.col + 1,
+      end_line = diagnostic.end_lnum + 1,
+      end_col = diagnostic.end_col + 1,
+    })
+
     table.insert(
       diagnostic_strings,
       string.format(
-        "%s (%s): %s",
-        Context.format({
-          buf = self.buf,
-          start_line = diagnostic.lnum + 1,
-          start_col = diagnostic.col + 1,
-          end_line = diagnostic.end_lnum + 1,
-          end_col = diagnostic.end_col + 1,
-        }),
+        "- %s (%s): %s",
+        location,
         diagnostic.source or "unknown source",
         diagnostic.message:gsub("%s+", " "):gsub("^%s", ""):gsub("%s$", "")
       )
     )
   end
-  return #diagnostics
-    .. " diagnostic"
-    .. (#diagnostics > 1 and "s" or "")
-    .. ": "
-    .. table.concat(diagnostic_strings, "; ")
+
+  return #diagnostics .. " diagnostics in " .. file_ref .. "\n" .. table.concat(diagnostic_strings, "\n")
 end
 
 ---Formatted quickfix list entries.