refactor: Move scroller into own testable module

lua/telescope/pickers.lua

@@ -14,6 +14,7 @@ local utils = require('telescope.utils')
 
 local layout_strategies = require('telescope.pickers.layout_strategies')
 local entry_display = require('telescope.pickers.entry_display')
+local p_scroller = require('telescope.pickers.scroller')
 
 local EntryManager = require('telescope.entry_manager')
 
@@ -66,7 +67,7 @@ function Picker:new(opts)
 
   local layout_strategy = get_default(opts.layout_strategy, config.values.layout_strategy)
 
-  return setmetatable({
+  local obj = setmetatable({
     prompt_title = get_default(opts.prompt_title, "Prompt"),
     results_title = get_default(opts.results_title, "Results"),
     preview_title = get_default(opts.preview_title, "Preview"),
@@ -91,7 +92,6 @@ function Picker:new(opts)
 
     sorting_strategy = get_default(opts.sorting_strategy, config.values.sorting_strategy),
     selection_strategy = get_default(opts.selection_strategy, config.values.selection_strategy),
-    scroll_strategy = get_default(opts.scroll_strategy, config.values.scroll_strategy),
 
     get_window_options = opts.get_window_options,
     layout_strategy = layout_strategy,
@@ -123,6 +123,13 @@ function Picker:new(opts)
 
     preview_cutoff = get_default(opts.preview_cutoff, config.values.preview_cutoff),
   }, self)
+
+
+  obj.scroller = p_scroller.create(
+    get_default(opts.scroll_strategy, config.values.scroll_strategy)
+  )
+
+  return obj
 end
 
 function Picker:_get_initial_window_options()
@@ -694,28 +701,10 @@ function Picker:reset_selection()
   self.multi_select = {}
 end
 
-function Picker:_handle_scroll_strategy(row)
-  if self.scroll_strategy == "cycle" then
-    if row >= self.max_results then
-      row = 0
-    elseif row < 0 then
-      row = self.max_results - 1
-    end
-  else
-    if row >= self.max_results then
-      row = self.max_results - 1
-    elseif row < 0 then
-      row = 0
-    end
-  end
-
-  return row
-end
-
 function Picker:set_selection(row)
   -- TODO: Loop around behavior?
   -- TODO: Scrolling past max results
-  row = self:_handle_scroll_strategy(row)
+  row = self.scroller(self.max_results, self.manager:num_results(), row)
 
   if not self:can_select_row(row) then
     -- If the current selected row exceeds number of currently displayed

lua/telescope/pickers/scroller.lua

@@ -0,0 +1,34 @@
+
+local scroller = {}
+
+scroller.create = function(strategy)
+  if strategy == 'cycle' then
+    return function(max_results, num_results, row)
+      local count = math.min(max_results, num_results)
+
+      if row >= count then
+        return 0
+      elseif row < 0 then
+        return count - 1
+      end
+
+      return row
+    end
+  elseif strategy == 'limit' or strategy == nil then
+    return function(max_results, num_results, row)
+      local count = math.min(max_results, num_results)
+
+      if row >= count then
+        return count - 1
+      elseif row < 0 then
+        return 0
+      end
+
+      return row
+    end
+  else
+    error("Unsupported strategy: ", strategy)
+  end
+end
+
+return scroller

lua/tests/automated/scroller_spec.lua

@@ -0,0 +1,56 @@
+local p_scroller = require('telescope.pickers.scroller')
+
+local eq = assert.are.same
+
+describe('scroller', function()
+  local max_results = 10
+
+  describe('cycle', function()
+    local cycle_scroller = p_scroller.create('cycle')
+
+    it('should return values within the max results', function()
+      eq(5, cycle_scroller(max_results, max_results, 5))
+    end)
+
+    it('should return 0 at 0', function()
+      eq(0, cycle_scroller(max_results, max_results, 0))
+    end)
+
+    it('should cycle you to the top 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(0, cycle_scroller(max_results, 5, 7))
+    end)
+  end)
+
+  describe('other', function()
+    local limit_scroller = p_scroller.create('limit')
+
+    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 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, 7))
+    end)
+  end)
+end)