neovim/test/functional/lua/iter_spec.lua

local helpers = require('test.functional.helpers')(after_each)
local eq = helpers.eq
local matches = helpers.matches
local pcall_err = helpers.pcall_err

describe('vim.iter', function()
  it('new() on iterable class instance', function()
    local rb = vim.ringbuf(3)
    rb:push('a')
    rb:push('b')

    local it = vim.iter(rb)
    eq({ 'a', 'b' }, it:totable())
  end)

  it('filter()', function()
    local function odd(v)
      return v % 2 ~= 0
    end

    local t = { 1, 2, 3, 4, 5 }
    eq({ 1, 3, 5 }, vim.iter(t):filter(odd):totable())
    eq(
      { 2, 4 },
      vim
        .iter(t)
        :filter(function(v)
          return not odd(v)
        end)
        :totable()
    )
    eq(
      {},
      vim
        .iter(t)
        :filter(function(v)
          return v > 5
        end)
        :totable()
    )

    do
      local it = vim.iter(ipairs(t))
      it:filter(function(i, v)
        return i > 1 and v < 5
      end)
      it:map(function(_, v)
        return v * 2
      end)
      eq({ 4, 6, 8 }, it:totable())
    end

    local it = vim.iter(string.gmatch('the quick brown fox', '%w+'))
    eq(
      { 'the', 'fox' },
      it:filter(function(s)
        return #s <= 3
      end):totable()
    )
  end)

  it('map()', function()
    local t = { 1, 2, 3, 4, 5 }
    eq(
      { 2, 4, 6, 8, 10 },
      vim
        .iter(t)
        :map(function(v)
          return 2 * v
        end)
        :totable()
    )

    local it = vim.gsplit(
      [[
      Line 1
      Line 2
      Line 3
      Line 4
    ]],
      '\n'
    )

    eq(
      { 'Lion 2', 'Lion 4' },
      vim
        .iter(it)
        :map(function(s)
          local lnum = s:match('(%d+)')
          if lnum and tonumber(lnum) % 2 == 0 then
            return vim.trim(s:gsub('Line', 'Lion'))
          end
        end)
        :totable()
    )
  end)

  it('for loops', function()
    local t = { 1, 2, 3, 4, 5 }
    local acc = 0
    for v in
      vim.iter(t):map(function(v)
        return v * 3
      end)
    do
      acc = acc + v
    end
    eq(45, acc)
  end)

  it('totable()', function()
    do
      local it = vim.iter({ 1, 2, 3 }):map(function(v)
        return v, v * v
      end)
      eq({ { 1, 1 }, { 2, 4 }, { 3, 9 } }, it:totable())
    end

    do
      local it = vim.iter(string.gmatch('1,4,lol,17,blah,2,9,3', '%d+')):map(tonumber)
      eq({ 1, 4, 17, 2, 9, 3 }, it:totable())
    end
  end)

  it('join()', function()
    eq('1, 2, 3', vim.iter({ 1, 2, 3 }):join(', '))
    eq('a|b|c|d', vim.iter(vim.gsplit('a|b|c|d', '|')):join('|'))
  end)

  it('next()', function()
    local it = vim.iter({ 1, 2, 3 }):map(function(v)
      return 2 * v
    end)
    eq(2, it:next())
    eq(4, it:next())
    eq(6, it:next())
    eq(nil, it:next())
  end)

  it('rev()', function()
    eq({ 3, 2, 1 }, vim.iter({ 1, 2, 3 }):rev():totable())

    local it = vim.iter(string.gmatch('abc', '%w'))
    matches('rev%(%) requires a list%-like table', pcall_err(it.rev, it))
  end)

  it('skip()', function()
    do
      local t = { 4, 3, 2, 1 }
      eq(t, vim.iter(t):skip(0):totable())
      eq({ 3, 2, 1 }, vim.iter(t):skip(1):totable())
      eq({ 2, 1 }, vim.iter(t):skip(2):totable())
      eq({ 1 }, vim.iter(t):skip(#t - 1):totable())
      eq({}, vim.iter(t):skip(#t):totable())
      eq({}, vim.iter(t):skip(#t + 1):totable())
    end

    do
      local function skip(n)
        return vim.iter(vim.gsplit('a|b|c|d', '|')):skip(n):totable()
      end
      eq({ 'a', 'b', 'c', 'd' }, skip(0))
      eq({ 'b', 'c', 'd' }, skip(1))
      eq({ 'c', 'd' }, skip(2))
      eq({ 'd' }, skip(3))
      eq({}, skip(4))
      eq({}, skip(5))
    end
  end)

  it('skipback()', function()
    do
      local t = { 4, 3, 2, 1 }
      eq(t, vim.iter(t):skipback(0):totable())
      eq({ 4, 3, 2 }, vim.iter(t):skipback(1):totable())
      eq({ 4, 3 }, vim.iter(t):skipback(2):totable())
      eq({ 4 }, vim.iter(t):skipback(#t - 1):totable())
      eq({}, vim.iter(t):skipback(#t):totable())
      eq({}, vim.iter(t):skipback(#t + 1):totable())
    end

    local it = vim.iter(vim.gsplit('a|b|c|d', '|'))
    matches('skipback%(%) requires a list%-like table', pcall_err(it.skipback, it, 0))
  end)

  it('slice()', function()
    local t = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }
    eq({ 3, 4, 5, 6, 7 }, vim.iter(t):slice(3, 7):totable())
    eq({}, vim.iter(t):slice(6, 5):totable())
    eq({}, vim.iter(t):slice(0, 0):totable())
    eq({ 1 }, vim.iter(t):slice(1, 1):totable())
    eq({ 1, 2 }, vim.iter(t):slice(1, 2):totable())
    eq({ 10 }, vim.iter(t):slice(10, 10):totable())
    eq({ 8, 9, 10 }, vim.iter(t):slice(8, 11):totable())

    local it = vim.iter(vim.gsplit('a|b|c|d', '|'))
    matches('slice%(%) requires a list%-like table', pcall_err(it.slice, it, 1, 3))
  end)

  it('nth()', function()
    do
      local t = { 4, 3, 2, 1 }
      eq(nil, vim.iter(t):nth(0))
      eq(4, vim.iter(t):nth(1))
      eq(3, vim.iter(t):nth(2))
      eq(2, vim.iter(t):nth(3))
      eq(1, vim.iter(t):nth(4))
      eq(nil, vim.iter(t):nth(5))
    end

    do
      local function nth(n)
        return vim.iter(vim.gsplit('a|b|c|d', '|')):nth(n)
      end
      eq(nil, nth(0))
      eq('a', nth(1))
      eq('b', nth(2))
      eq('c', nth(3))
      eq('d', nth(4))
      eq(nil, nth(5))
    end
  end)

  it('nthback()', function()
    do
      local t = { 4, 3, 2, 1 }
      eq(nil, vim.iter(t):nthback(0))
      eq(1, vim.iter(t):nthback(1))
      eq(2, vim.iter(t):nthback(2))
      eq(3, vim.iter(t):nthback(3))
      eq(4, vim.iter(t):nthback(4))
      eq(nil, vim.iter(t):nthback(5))
    end

    local it = vim.iter(vim.gsplit('a|b|c|d', '|'))
    matches('skipback%(%) requires a list%-like table', pcall_err(it.nthback, it, 1))
  end)

  it('take()', function()
    do
      local t = { 4, 3, 2, 1 }
      eq({}, vim.iter(t):take(0):totable())
      eq({ 4 }, vim.iter(t):take(1):totable())
      eq({ 4, 3 }, vim.iter(t):take(2):totable())
      eq({ 4, 3, 2 }, vim.iter(t):take(3):totable())
      eq({ 4, 3, 2, 1 }, vim.iter(t):take(4):totable())
      eq({ 4, 3, 2, 1 }, vim.iter(t):take(5):totable())
    end

    do
      local t = { 4, 3, 2, 1 }
      local it = vim.iter(t)
      eq({ 4, 3 }, it:take(2):totable())
      -- tail is already set from the previous take()
      eq({ 4, 3 }, it:take(3):totable())
    end

    do
      local it = vim.iter(vim.gsplit('a|b|c|d', '|'))
      eq({ 'a', 'b' }, it:take(2):totable())
      -- non-array iterators are consumed by take()
      eq({}, it:take(2):totable())
    end
  end)

  it('any()', function()
    local function odd(v)
      return v % 2 ~= 0
    end

    do
      local t = { 4, 8, 9, 10 }
      eq(true, vim.iter(t):any(odd))
    end

    do
      local t = { 4, 8, 10 }
      eq(false, vim.iter(t):any(odd))
    end

    do
      eq(
        true,
        vim.iter(vim.gsplit('a|b|c|d', '|')):any(function(s)
          return s == 'd'
        end)
      )
      eq(
        false,
        vim.iter(vim.gsplit('a|b|c|d', '|')):any(function(s)
          return s == 'e'
        end)
      )
    end
  end)

  it('all()', function()
    local function odd(v)
      return v % 2 ~= 0
    end

    do
      local t = { 3, 5, 7, 9 }
      eq(true, vim.iter(t):all(odd))
    end

    do
      local t = { 3, 5, 7, 10 }
      eq(false, vim.iter(t):all(odd))
    end

    do
      eq(
        true,
        vim.iter(vim.gsplit('a|a|a|a', '|')):all(function(s)
          return s == 'a'
        end)
      )
      eq(
        false,
        vim.iter(vim.gsplit('a|a|a|b', '|')):all(function(s)
          return s == 'a'
        end)
      )
    end
  end)

  it('last()', function()
    local s = 'abcdefghijklmnopqrstuvwxyz'
    eq('z', vim.iter(vim.split(s, '')):last())
    eq('z', vim.iter(vim.gsplit(s, '')):last())
  end)

  it('enumerate()', function()
    local it = vim.iter(vim.gsplit('abc', '')):enumerate()
    eq({ 1, 'a' }, { it:next() })
    eq({ 2, 'b' }, { it:next() })
    eq({ 3, 'c' }, { it:next() })
    eq({}, { it:next() })
  end)

  it('peek()', function()
    do
      local it = vim.iter({ 3, 6, 9, 12 })
      eq(3, it:peek())
      eq(3, it:peek())
      eq(3, it:next())
    end

    do
      local it = vim.iter(vim.gsplit('hi', ''))
      matches('peek%(%) requires a list%-like table', pcall_err(it.peek, it))
    end
  end)

  it('find()', function()
    local t = { 3, 6, 9, 12 }
    eq(12, vim.iter(t):find(12))
    eq(nil, vim.iter(t):find(15))
    eq(
      12,
      vim.iter(t):find(function(v)
        return v % 4 == 0
      end)
    )

    do
      local it = vim.iter(t)
      local pred = function(v)
        return v % 3 == 0
      end
      eq(3, it:find(pred))
      eq(6, it:find(pred))
      eq(9, it:find(pred))
      eq(12, it:find(pred))
      eq(nil, it:find(pred))
    end

    do
      local it = vim.iter(vim.gsplit('AbCdE', ''))
      local pred = function(s)
        return s:match('[A-Z]')
      end
      eq('A', it:find(pred))
      eq('C', it:find(pred))
      eq('E', it:find(pred))
      eq(nil, it:find(pred))
    end
  end)

  it('rfind()', function()
    local t = { 1, 2, 3, 2, 1 }
    do
      local it = vim.iter(t)
      eq(1, it:rfind(1))
      eq(1, it:rfind(1))
      eq(nil, it:rfind(1))
    end

    do
      local it = vim.iter(t):enumerate()
      local pred = function(i)
        return i % 2 ~= 0
      end
      eq({ 5, 1 }, { it:rfind(pred) })
      eq({ 3, 3 }, { it:rfind(pred) })
      eq({ 1, 1 }, { it:rfind(pred) })
      eq(nil, it:rfind(pred))
    end

    do
      local it = vim.iter(vim.gsplit('AbCdE', ''))
      matches('rfind%(%) requires a list%-like table', pcall_err(it.rfind, it, 'E'))
    end
  end)

  it('nextback()', function()
    do
      local it = vim.iter({ 1, 2, 3, 4 })
      eq(4, it:nextback())
      eq(3, it:nextback())
      eq(2, it:nextback())
      eq(1, it:nextback())
      eq(nil, it:nextback())
      eq(nil, it:nextback())
    end

    do
      local it = vim.iter(vim.gsplit('hi', ''))
      matches('nextback%(%) requires a list%-like table', pcall_err(it.nextback, it))
    end
  end)

  it('peekback()', function()
    do
      local it = vim.iter({ 1, 2, 3, 4 })
      eq(4, it:peekback())
      eq(4, it:peekback())
      eq(4, it:nextback())
    end

    do
      local it = vim.iter(vim.gsplit('hi', ''))
      matches('peekback%(%) requires a list%-like table', pcall_err(it.peekback, it))
    end
  end)

  it('fold()', function()
    local t = { 1, 2, 3, 4, 5 }
    eq(
      115,
      vim.iter(t):fold(100, function(acc, v)
        return acc + v
      end)
    )
    eq(
      { 5, 4, 3, 2, 1 },
      vim.iter(t):fold({}, function(acc, v)
        table.insert(acc, 1, v)
        return acc
      end)
    )
  end)

  it('handles map-like tables', function()
    local it = vim.iter({ a = 1, b = 2, c = 3 }):map(function(k, v)
      if v % 2 ~= 0 then
        return k:upper(), v * 2
      end
    end)

    local t = it:fold({}, function(t, k, v)
      t[k] = v
      return t
    end)
    eq({ A = 2, C = 6 }, t)
  end)

  it('handles table values mid-pipeline', function()
    local map = {
      item = {
        file = 'test',
      },
      item_2 = {
        file = 'test',
      },
      item_3 = {
        file = 'test',
      },
    }

    local output = vim
      .iter(map)
      :map(function(key, value)
        return { [key] = value.file }
      end)
      :totable()

    table.sort(output, function(a, b)
      return next(a) < next(b)
    end)

    eq({
      { item = 'test' },
      { item_2 = 'test' },
      { item_3 = 'test' },
    }, output)
  end)
end)