fix: alternate buffer preservation (#43)

lua/oil/init.lua

@@ -660,7 +660,8 @@ M.setup = function(opts)
     group = aug,
     pattern = "*",
     callback = function()
-      if vim.bo.filetype ~= "oil" then
+      local util = require("oil.util")
+      if not util.is_oil_bufnr(0) then
         vim.api.nvim_win_set_var(0, "oil_original_buffer", vim.api.nvim_get_current_buf())
         vim.api.nvim_win_set_var(0, "oil_original_alternate", vim.fn.bufnr("#"))
       end
@@ -719,7 +720,8 @@ M.setup = function(opts)
     pattern = "*",
     nested = true,
     callback = function(params)
-      if vim.bo[params.buf].filetype ~= "oil" or vim.w.oil_did_enter then
+      local util = require("oil.util")
+      if not util.is_oil_bufnr(params.buf) or vim.w.oil_did_enter then
         return
       end
       -- This new window is a split off of an oil window. We need to transfer the window

lua/oil/util.lua

@@ -489,6 +489,16 @@ M.run_in_fullscreen_win = function(bufnr, callback)
   vim.cmd.close({ count = winnr, mods = { noautocmd = true, emsg_silent = true } })
 end
 
+---@param bufnr integer
+---@return boolean
+M.is_oil_bufnr = function(bufnr)
+  if vim.bo[bufnr].filetype == "oil" then
+    return true
+  end
+  local scheme = M.parse_url(vim.api.nvim_buf_get_name(bufnr))
+  return config.adapters[scheme] or config.adapter_aliases[scheme]
+end
+
 ---This is a hack so we don't end up in insert mode after starting a task
 ---@param prev_mode string The vim mode we were in before opening a terminal
 M.hack_around_termopen_autocmd = function(prev_mode)

tests/altbuf_spec.lua

@@ -16,6 +16,19 @@ a.describe("Alternate buffer", function()
     assert.equals("foo", vim.fn.expand("#"))
   end)
 
+  a.it("sets previous buffer as alternate when editing url file", function()
+    vim.cmd.edit({ args = { "foo" } })
+    oil.open()
+    test_util.wait_for_autocmd("BufReadPost")
+    local readme = fs.join(vim.fn.getcwd(), "README.md")
+    vim.cmd.edit({ args = { "oil://" .. fs.os_to_posix_path(readme) } })
+    -- We're gonna jump around to 2 different buffers
+    test_util.wait_for_autocmd("BufEnter")
+    test_util.wait_for_autocmd("BufEnter")
+    assert.equals(readme, vim.api.nvim_buf_get_name(0))
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
   a.it("sets previous buffer as alternate when editing oil://", function()
     vim.cmd.edit({ args = { "foo" } })
     vim.cmd.edit({ args = { "oil://" .. fs.os_to_posix_path(vim.fn.getcwd()) } })