api: Support getting the number of a window/tabpage

In order to provide better compatibility with the classic bindings, the
API needs to provide the ability to query the number (really index) of
the window/tabpage.

This is needed for neovim/python-client#87, as discussed in
neovim/neovim#1898.

Signed-off-by: James McCoy <jamessan@jamessan.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/test/functional/api/tabpage_spec.lua b/test/functional/api/tabpage_spec.lua
index 47dede8b44..90940e9577 100644
--- a/test/functional/api/tabpage_spec.lua
+++ b/test/functional/api/tabpage_spec.lua
@@ -51,6 +51,22 @@ describe('tabpage_* functions', function()
     end)
   end)
 
+  describe('get_number', function()
+    it('works', function()
+      local tabs = nvim('list_tabpages')
+      eq(1, tabpage('get_number', tabs[1]))
+
+      nvim('command', 'tabnew')
+      local tab1, tab2 = unpack(nvim('list_tabpages'))
+      eq(1, tabpage('get_number', tab1))
+      eq(2, tabpage('get_number', tab2))
+
+      nvim('command', '-tabmove')
+      eq(2, tabpage('get_number', tab1))
+      eq(1, tabpage('get_number', tab2))
+    end)
+  end)
+
   describe('is_valid', function()
     it('works', function()
       nvim('command', 'tabnew')