modules: Make luci-base sufficient to use luci apps

Per the discussion in https://github.com/openwrt/luci/issues/869, make
luci-base sufficient to login, logout, and review and apply or revert
uci changes.  This allows most luci-app-xxx to work without having
luci-mod-admin-full installed.

It has been tested with some apps and not luci-mod-admin-full, as well
as with luci-mod-admin-full (to make sure the usual case doesn't break).

Instead of creating a new module namespace (e.g. 'Base') we reduce the
opportunities for breakage by having luci-base take over the 'shell' of
the 'Administration' (admin/....) namespace.

Since admin is assumed by all current building LuCI components (including
Freifunk), this doesn't introduce the 'Administration' tab into any
situation where it would not already be present (but includes it where it
was before).

We also add a "Component not installed" page to avoid fatal errors and
backtrace when e.g. luci-mod-admin-full is not installed.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

11 files changed, 99 insertions, 55 deletions

diff --git a/modules/luci-base/luasrc/controller/admin/index.lua b/modules/luci-base/luasrc/controller/admin/index.lua
new file mode 100644
index 0000000000..39e6e573b1
--- /dev/null
+++ b/modules/luci-base/luasrc/controller/admin/index.lua
@@ -0,0 +1,82 @@
+-- Copyright 2008 Steven Barth <steven@midlink.org>
+-- Licensed to the public under the Apache License 2.0.
+
+module("luci.controller.admin.index", package.seeall)
+
+function index()
+	function toplevel_page(page, preflookup, preftarget)
+		if preflookup and preftarget then
+			if lookup(preflookup) then
+				page.target = preftarget
+			end
+		end
+
+		if not page.target then
+			page.target = firstchild()
+		end
+	end
+
+	local root = node()
+	if not root.target then
+		root.target = alias("admin")
+		root.index = true
+	end
+
+	local page   = node("admin")
+	page.title   = _("Administration")
+	page.order   = 10
+	page.sysauth = "root"
+	page.sysauth_authenticator = "htmlauth"
+	page.ucidata = true
+	page.index = true
+	toplevel_page(page, "admin/status/overview", alias("admin", "status"))
+
+	-- Empty menu tree to be populated by addons and modules
+
+	page = node("admin", "status")
+	page.title = _("Status")
+	page.order = 10
+	page.index = true
+	-- overview is from mod-admin-full
+	toplevel_page(page, "admin/status/overview", alias("admin", "status", "overview"))
+
+	page = node("admin", "system")
+	page.title = _("System")
+	page.order = 20
+	page.index = true
+	-- system/system is from mod-admin-full
+	toplevel_page(page, "admin/system/system", alias("admin", "system", "system")) 
+
+	-- Only used if applications add items
+	page = node("admin", "services")
+	page.title = _("Services")
+	page.order = 40
+	page.index = true
+	toplevel_page(page, false, false)
+
+	-- Even for mod-admin-full network just uses first submenu item as landing
+	page = node("admin", "network")
+	page.title = _("Network")
+	page.order = 50
+	page.index = true
+	toplevel_page(page, false, false)
+
+	-- Logout is last
+	entry({"admin", "logout"}, call("action_logout"), _("Logout"), 999)
+end
+
+function action_logout()
+	local dsp = require "luci.dispatcher"
+	local utl = require "luci.util"
+	local sid = dsp.context.authsession
+
+	if sid then
+		utl.ubus("session", "destroy", { ubus_rpc_session = sid })
+
+		luci.http.header("Set-Cookie", "sysauth=%s; expires=%s; path=%s/" %{
+			sid, 'Thu, 01 Jan 1970 01:00:00 GMT', dsp.build_url()
+		})
+	end
+
+	luci.http.redirect(dsp.build_url())
+end
diff --git a/modules/luci-mod-admin-full/luasrc/controller/admin/uci.lua b/modules/luci-base/luasrc/controller/admin/uci.lua
index 1d955dd982..1d955dd982 100644
--- a/modules/luci-mod-admin-full/luasrc/controller/admin/uci.lua
+++ b/modules/luci-base/luasrc/controller/admin/uci.lua
diff --git a/modules/luci-base/luasrc/dispatcher.lua b/modules/luci-base/luasrc/dispatcher.lua
index 6cf2712eb4..09d5d72846 100644
--- a/modules/luci-base/luasrc/dispatcher.lua
+++ b/modules/luci-base/luasrc/dispatcher.lua
@@ -741,11 +741,12 @@ function _firstchild()
 	  end
    end
 
-   assert(lowest ~= nil,
-		  "The requested node contains no childs, unable to redispatch")
-
-   path[#path+1] = lowest
-   dispatch(path)
+   if lowest == nil then
+	require "luci.template".render("empty_node_placeholder")
+   else
+	path[#path+1] = lowest
+	dispatch(path)
+   end
 end
 
 function firstchild()
diff --git a/modules/luci-mod-admin-full/luasrc/view/admin_uci/changelog.htm b/modules/luci-base/luasrc/view/admin_uci/changelog.htm
index 8a162c88b6..8a162c88b6 100644
--- a/modules/luci-mod-admin-full/luasrc/view/admin_uci/changelog.htm
+++ b/modules/luci-base/luasrc/view/admin_uci/changelog.htm
diff --git a/modules/luci-mod-admin-full/luasrc/view/admin_uci/changes.htm b/modules/luci-base/luasrc/view/admin_uci/changes.htm
index 43bd7c23fb..43bd7c23fb 100644
--- a/modules/luci-mod-admin-full/luasrc/view/admin_uci/changes.htm
+++ b/modules/luci-base/luasrc/view/admin_uci/changes.htm
diff --git a/modules/luci-mod-admin-full/luasrc/view/admin_uci/revert.htm b/modules/luci-base/luasrc/view/admin_uci/revert.htm
index d8fd3de01e..d8fd3de01e 100644
--- a/modules/luci-mod-admin-full/luasrc/view/admin_uci/revert.htm
+++ b/modules/luci-base/luasrc/view/admin_uci/revert.htm
diff --git a/modules/luci-base/luasrc/view/empty_node_placeholder.htm b/modules/luci-base/luasrc/view/empty_node_placeholder.htm
new file mode 100644
index 0000000000..b7e276b960
--- /dev/null
+++ b/modules/luci-base/luasrc/view/empty_node_placeholder.htm
@@ -0,0 +1,11 @@
+<%#
+ Copyright 2010 Jo-Philipp Wich <jow@openwrt.org>
+ Copyright 2018 Daniel F. Dickinson <cshored@thecshore.com>
+ Licensed to the public under the Apache License 2.0.
+-%>
+
+<%+header%>
+
+<p>Component not present.</p>
+
+<%+footer%>
diff --git a/modules/luci-mod-admin-full/luasrc/controller/admin/index.lua b/modules/luci-mod-admin-full/luasrc/controller/admin/index.lua
deleted file mode 100644
index cc8c2e3ae6..0000000000
--- a/modules/luci-mod-admin-full/luasrc/controller/admin/index.lua
+++ /dev/null
@@ -1,42 +0,0 @@
--- Copyright 2008 Steven Barth <steven@midlink.org>
--- Licensed to the public under the Apache License 2.0.
-
-module("luci.controller.admin.index", package.seeall)
-
-function index()
-	local root = node()
-	if not root.target then
-		root.target = alias("admin")
-		root.index = true
-	end
-
-	local page   = node("admin")
-	page.target  = firstchild()
-	page.title   = _("Administration")
-	page.order   = 10
-	page.sysauth = "root"
-	page.sysauth_authenticator = "htmlauth"
-	page.ucidata = true
-	page.index = true
-
-	-- Empty services menu to be populated by addons
-	entry({"admin", "services"}, firstchild(), _("Services"), 40).index = true
-
-	entry({"admin", "logout"}, call("action_logout"), _("Logout"), 90)
-end
-
-function action_logout()
-	local dsp = require "luci.dispatcher"
-	local utl = require "luci.util"
-	local sid = dsp.context.authsession
-
-	if sid then
-		utl.ubus("session", "destroy", { ubus_rpc_session = sid })
-
-		luci.http.header("Set-Cookie", "sysauth=%s; expires=%s; path=%s/" %{
-			sid, 'Thu, 01 Jan 1970 01:00:00 GMT', dsp.build_url()
-		})
-	end
-
-	luci.http.redirect(dsp.build_url())
-end
diff --git a/modules/luci-mod-admin-full/luasrc/controller/admin/network.lua b/modules/luci-mod-admin-full/luasrc/controller/admin/network.lua
index c45605a983..c4e1c3aa16 100644
--- a/modules/luci-mod-admin-full/luasrc/controller/admin/network.lua
+++ b/modules/luci-mod-admin-full/luasrc/controller/admin/network.lua
@@ -8,12 +8,6 @@ function index()
 	local uci = require("luci.model.uci").cursor()
 	local page
 
-	page = node("admin", "network")
-	page.target = firstchild()
-	page.title  = _("Network")
-	page.order  = 50
-	page.index  = true
-
 --	if page.inreq then
 		local has_switch = false
 
diff --git a/modules/luci-mod-admin-full/luasrc/controller/admin/status.lua b/modules/luci-mod-admin-full/luasrc/controller/admin/status.lua
index ff95f3d915..4f04cce545 100644
--- a/modules/luci-mod-admin-full/luasrc/controller/admin/status.lua
+++ b/modules/luci-mod-admin-full/luasrc/controller/admin/status.lua
@@ -5,7 +5,6 @@
 module("luci.controller.admin.status", package.seeall)
 
 function index()
-	entry({"admin", "status"}, alias("admin", "status", "overview"), _("Status"), 20).index = true
 	entry({"admin", "status", "overview"}, template("admin_status/index"), _("Overview"), 1)
 
 	entry({"admin", "status", "iptables"}, template("admin_status/iptables"), _("Firewall"), 2).leaf = true
diff --git a/modules/luci-mod-admin-full/luasrc/controller/admin/system.lua b/modules/luci-mod-admin-full/luasrc/controller/admin/system.lua
index 46d2e36c32..4e83769ee0 100644
--- a/modules/luci-mod-admin-full/luasrc/controller/admin/system.lua
+++ b/modules/luci-mod-admin-full/luasrc/controller/admin/system.lua
@@ -7,7 +7,6 @@ module("luci.controller.admin.system", package.seeall)
 function index()
 	local fs = require "nixio.fs"
 
-	entry({"admin", "system"}, alias("admin", "system", "system"), _("System"), 30).index = true
 	entry({"admin", "system", "system"}, cbi("admin_system/system"), _("System"), 1)
 	entry({"admin", "system", "clock_status"}, post_on({ set = true }, "action_clock_status"))