Fix: scroller for descending (#327)

lua/telescope/pickers.lua

@@ -126,7 +126,8 @@ function Picker:new(opts)
 
 
   obj.scroller = p_scroller.create(
-    get_default(opts.scroll_strategy, config.values.scroll_strategy)
+    get_default(opts.scroll_strategy, config.values.scroll_strategy),
+    obj.sorting_strategy
   )
 
   return obj

lua/telescope/pickers/scroller.lua

@@ -1,10 +1,33 @@
-
 local scroller = {}
 
-scroller.create = function(strategy)
+local calc_count_fn = function(sorting_strategy)
+  if sorting_strategy == 'ascending' then
+    return function(a, b) return math.min(a, b) end
+  else
+    return function(a, b, row)
+      if a == b or not row then
+        return math.max(a, b)
+      else
+        local x = a - b
+        if row < x then
+          return math.max(a, b) - 1, true
+        elseif row == a then
+          return x, true
+        else
+          return math.max(a, b)
+        end
+      end
+    end
+  end
+end
+
+scroller.create = function(strategy, sorting_strategy)
+  local calc_count = calc_count_fn(sorting_strategy)
+
   if strategy == 'cycle' then
     return function(max_results, num_results, row)
-      local count = math.min(max_results, num_results)
+      local count, b = calc_count(max_results, num_results, row)
+      if b then return count end
 
       if row >= count then
         return 0
@@ -16,7 +39,7 @@ scroller.create = function(strategy)
     end
   elseif strategy == 'limit' or strategy == nil then
     return function(max_results, num_results, row)
-      local count = math.min(max_results, num_results)
+      local count = calc_count(max_results, num_results)
 
       if row >= count then
         return count - 1

lua/tests/automated/scroller_spec.lua

@@ -5,8 +5,8 @@ local eq = assert.are.same
 describe('scroller', function()
   local max_results = 10
 
-  describe('cycle', function()
-    local cycle_scroller = p_scroller.create('cycle')
+  describe('ascending cycle', function()
+    local cycle_scroller = p_scroller.create('cycle', 'ascending')
 
     it('should return values within the max results', function()
       eq(5, cycle_scroller(max_results, max_results, 5))
@@ -29,8 +29,8 @@ describe('scroller', function()
     end)
   end)
 
-  describe('other', function()
-    local limit_scroller = p_scroller.create('limit')
+  describe('ascending limit', function()
+    local limit_scroller = p_scroller.create('limit', 'ascending')
 
     it('should return values within the max results', function()
       eq(5, limit_scroller(max_results, max_results, 5))
@@ -44,7 +44,7 @@ describe('scroller', function()
       eq(0, limit_scroller(max_results, max_results, -1))
     end)
 
-    it('should cycle you to 0 when you go past the results', function()
+    it('should not cycle you to 0 when you go past the results', function()
       eq(max_results - 1, limit_scroller(max_results, max_results, max_results + 1))
     end)
 
@@ -53,4 +53,53 @@ describe('scroller', function()
       eq(current - 1, limit_scroller(max_results, current, 7))
     end)
   end)
+
+  describe('descending cycle', function()
+    local cycle_scroller = p_scroller.create('cycle', 'descending')
+
+    it('should return values within the max results', function()
+      eq(5, cycle_scroller(max_results, max_results, 5))
+    end)
+
+    it('should return max_results - 1 at 0', function()
+      eq(0, cycle_scroller(max_results, max_results, 0))
+    end)
+
+    it('should cycle you to the bot when you go below 0', function()
+      eq(max_results - 1, cycle_scroller(max_results, max_results, -1))
+    end)
+
+    it('should cycle you to 0 when you go past the results', function()
+      eq(0, cycle_scroller(max_results, max_results, max_results + 1))
+    end)
+
+    it('should cycle when current results is less than max_results', function()
+      eq(9, cycle_scroller(max_results, 5, 4))
+    end)
+  end)
+
+  describe('descending limit', function()
+    local limit_scroller = p_scroller.create('limit', 'descending')
+
+    it('should return values within the max results', function()
+      eq(5, limit_scroller(max_results, max_results, 5))
+    end)
+
+    it('should return 0 at 0', function()
+      eq(0, limit_scroller(max_results, max_results, 0))
+    end)
+
+    it('should not cycle', function()
+      eq(0, limit_scroller(max_results, max_results, -1))
+    end)
+
+    it('should not cycle you to 0 when you go past the results', function()
+      eq(max_results - 1, limit_scroller(max_results, max_results, max_results + 1))
+    end)
+
+    it('should stay at current results when current results is less than max_results', function()
+      local current = 5
+      eq(current - 1, limit_scroller(max_results, current, 4))
+    end)
+  end)
 end)