fix: preserve the alternate buffer (#20)

tests/altbuf_spec.lua

@@ -0,0 +1,49 @@
+local oil = require("oil")
+local test_util = require("tests.test_util")
+local fs = require("oil.fs")
+
+describe("Alternate buffer", function()
+  after_each(function()
+    test_util.reset_editor()
+  end)
+
+  it("sets previous buffer as alternate", function()
+    vim.cmd.edit({ args = { "foo" } })
+    oil.open()
+    vim.cmd.edit({ args = { "bar" } })
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
+  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()) } })
+    vim.cmd.edit({ args = { "bar" } })
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
+  it("preserves alternate buffer if editing the same file", function()
+    vim.cmd.edit({ args = { "foo" } })
+    vim.cmd.edit({ args = { "bar" } })
+    oil.open()
+    vim.cmd.edit({ args = { "bar" } })
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
+  it("preserves alternate buffer if discarding changes", function()
+    vim.cmd.edit({ args = { "foo" } })
+    vim.cmd.edit({ args = { "bar" } })
+    oil.open()
+    oil.close()
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+
+  it("sets previous buffer as alternate after multi-dir hops", function()
+    vim.cmd.edit({ args = { "foo" } })
+    oil.open()
+    oil.open()
+    oil.open()
+    oil.open()
+    vim.cmd.edit({ args = { "bar" } })
+    assert.equals("foo", vim.fn.expand("#"))
+  end)
+end)

tests/test_util.lua

@@ -0,0 +1,19 @@
+local M = {}
+
+M.reset_editor = function()
+  require("oil").setup({})
+  vim.cmd.tabonly({ mods = { silent = true } })
+  for i, winid in ipairs(vim.api.nvim_tabpage_list_wins(0)) do
+    if i > 1 then
+      vim.api.nvim_win_close(winid, true)
+    end
+  end
+  vim.api.nvim_win_set_buf(0, vim.api.nvim_create_buf(false, true))
+  for _, bufnr in ipairs(vim.api.nvim_list_bufs()) do
+    if vim.api.nvim_buf_get_option(bufnr, "buflisted") then
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+    end
+  end
+end
+
+return M