fix: couple bugs with multiple results and varargs (...) (#515)

* fix(vararg.rotate): edge cases and nil arguments

- zero argument rotation returned one value (a global by the name A0)
- the generic fallback dropped the first argument and trailing nils

* fix: functional.partial & fun.bind

These only worked for binding exactly one parameter.

* Include generated rotate.lua file in linting

Author: juntuu

.luacheckrc

@@ -27,7 +27,6 @@ read_globals = {
 exclude_files = {
   "lua/plenary/profile/lua_profiler.lua",
   "lua/plenary/profile/memory_profiler.lua",
-  "lua/plenary/vararg/rotate.lua",
   "lua/plenary/async_lib/*.lua",
 }
 

lua/plenary/fun.lua

@@ -1,20 +1,6 @@
-local tbl = require "plenary.tbl"
-
 local M = {}
 
-function M.bind(fn, ...)
-  if select("#", ...) == 1 then
-    local arg = ...
-    return function(...)
-      fn(arg, ...)
-    end
-  end
-
-  local args = tbl.pack(...)
-  return function(...)
-    fn(tbl.unpack(args), ...)
-  end
-end
+M.bind = require("plenary.functional").partial
 
 function M.arify(fn, argc)
   return function(...)

lua/plenary/functional.lua

@@ -16,11 +16,17 @@ function f.join(array, sep)
   return table.concat(vim.tbl_map(tostring, array), sep)
 end
 
-function f.partial(fun, ...)
-  local args = { ... }
-  return function(...)
-    return fun(unpack(args), ...)
+local function bind_n(fn, n, a, ...)
+  if n == 0 then
+    return fn
   end
+  return bind_n(function(...)
+    return fn(a, ...)
+  end, n - 1, ...)
+end
+
+function f.partial(fun, ...)
+  return bind_n(fun, select("#", ...), ...)
 end
 
 function f.any(fun, iterable)

lua/plenary/vararg/rotate.lua

@@ -6,10 +6,6 @@ local tbl = require "plenary.tbl"
 
 local rotate_lookup = {}
 
-rotate_lookup[0] = function()
-  return A0
-end
-
 rotate_lookup[1] = function(A0)
   return A0
 end
@@ -71,12 +67,16 @@ rotate_lookup[15] = function(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A
 end
 
 local function rotate_n(first, ...)
+  local n = select("#", ...) + 1
   local args = tbl.pack(...)
-  args[#args + 1] = first
-  return tbl.unpack(args)
+  args[n] = first
+  return tbl.unpack(args, 1, n)
 end
 
 local function rotate(nargs, ...)
+  if nargs == nil or nargs < 1 then
+    return
+  end
   return (rotate_lookup[nargs] or rotate_n)(...)
 end
 

scripts/vararg/rotate.lua

@@ -7,19 +7,23 @@ local tbl = require('plenary.tbl')
 
 local rotate_lookup = {}
 
-{% for n in range(0, amount) %}
+{% for n in range(1, amount) %}
   rotate_lookup[{{n}}] = function ({% for n in range(n) %} A{{n}} {{ ", " if not loop.last else "" }} {% endfor %})
     return {% for n in range(1, n) %} A{{n}}, {% endfor %} A0
   end
 {% endfor %}
 
 local function rotate_n(first, ...)
+  local n = select("#", ...) + 1
   local args = tbl.pack(...)
-  args[#args+1] = first
-  return tbl.unpack(args)
+  args[n] = first
+  return tbl.unpack(args, 1, n)
 end
 
 local function rotate(nargs, ...)
+  if nargs == nil or nargs < 1 then
+    return
+  end
   return (rotate_lookup[nargs] or rotate_n)(...)
 end
 

tests/plenary/functional_spec.lua

@@ -0,0 +1,18 @@
+local f = require "plenary.functional"
+
+describe("functional", function()
+  describe("partial", function()
+    local function args(...)
+      assert.is.equal(4, select("#", ...))
+      return table.concat({ ... }, ",")
+    end
+    it("should bind correct parameters", function()
+      local expected = args(1, 2, 3, 4)
+      assert.is.equal(expected, f.partial(args)(1, 2, 3, 4))
+      assert.is.equal(expected, f.partial(args, 1)(2, 3, 4))
+      assert.is.equal(expected, f.partial(args, 1, 2)(3, 4))
+      assert.is.equal(expected, f.partial(args, 1, 2, 3)(4))
+      assert.is.equal(expected, f.partial(args, 1, 2, 3, 4)())
+    end)
+  end)
+end)

tests/plenary/rotate_spec.lua

@@ -5,13 +5,26 @@ local eq = function(a, b)
 end
 
 describe("rotate", function()
+  it("should return as many values, as the first argument", function()
+    local args = {}
+    for _ = 0, 20 do
+      local n = select("#", unpack(args))
+      assert.is.equal(n, select("#", rotate(n, unpack(args))))
+      args[#args + 1] = n
+    end
+  end)
+
   it("should rotate varargs", function()
     eq({ rotate(3, 1, 2, 3) }, { 2, 3, 1 })
     eq({ rotate(9, 1, 2, 3, 4, 5, 6, 7, 8, 9) }, { 2, 3, 4, 5, 6, 7, 8, 9, 1 })
   end)
 
+  it("should rotate zero", function()
+    assert.is.equal(0, select("#", rotate(0)))
+  end)
+
   it("should rotate none", function()
-    eq({ rotate() }, {})
+    assert.is.equal(0, select("#", rotate()))
   end)
 
   it("should rotate one", function()