system('foo &', 'bar'): Show error, don't crash.

Closes #3529
Closes #5241

In Vim,
    :echo system('cat - &', 'foo')
works because for both system() and :! Vim writes input to a temp file and uses
shell syntax to redirect the file to the backgrounded `cat` (get_cmd_output()
.. make_filter_cmd()).

In Nvim,
    :echo system('cat - &', 'foo')
fails because we write the input directly via pipes (shell.c:do_os_system()),
but (per POSIX[1]) backgrounded process input stream is redirected from
/dev/null (unless overridden by shell redirection; supported only by some shells
[2]), so our writes are ignored, the process exits quickly, and if we are
writing data larger than the buffer size we'll see EPIPE.

This still works:
    :%w !tee > foo1358.txt &
but this does not:
    :%w !tee foo1358.txt &
though it *should* (why doesn't it?) because we still do the temp file dance
in do_bang() .. do_filter().

[1] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_03_02
[2] http://unix.stackexchange.com/a/71218

1 files changed, 385 insertions, 0 deletions

diff --git a/test/functional/eval/system_spec.lua b/test/functional/eval/system_spec.lua
new file mode 100644
index 0000000000..b8f1f87f30
--- /dev/null
+++ b/test/functional/eval/system_spec.lua
@@ -0,0 +1,385 @@
+local helpers = require('test.functional.helpers')(after_each)
+local eq, clear, eval, feed, nvim =
+  helpers.eq, helpers.clear, helpers.eval, helpers.feed, helpers.nvim
+
+local Screen = require('test.functional.ui.screen')
+
+if helpers.pending_win32(pending) then return end
+
+local function create_file_with_nuls(name)
+  return function()
+    feed('ipart1<C-V>000part2<C-V>000part3<ESC>:w '..name..'<CR>')
+    eval('1')  -- wait for the file to be created
+  end
+end
+
+local function delete_file(name)
+  return function()
+    eval("delete('"..name.."')")
+  end
+end
+
+-- Some tests require the xclip program and a x server.
+local xclip = nil
+do
+  if os.getenv('DISPLAY') then
+    xclip = (os.execute('command -v xclip > /dev/null 2>&1') == 0)
+  end
+end
+
+describe('system()', function()
+  before_each(clear)
+
+  it('sets the v:shell_error variable', function()
+    eval([[system("sh -c 'exit'")]])
+    eq(0, eval('v:shell_error'))
+    eval([[system("sh -c 'exit 1'")]])
+    eq(1, eval('v:shell_error'))
+    eval([[system("sh -c 'exit 5'")]])
+    eq(5, eval('v:shell_error'))
+    eval([[system('this-should-not-exist')]])
+    eq(127, eval('v:shell_error'))
+  end)
+
+  describe('executes shell function if passed a string', function()
+    local screen
+
+    before_each(function()
+        clear()
+        screen = Screen.new()
+        screen:attach()
+    end)
+
+    after_each(function()
+        screen:detach()
+    end)
+
+    it('`echo` and waits for its return', function()
+      feed(':call system("echo")<cr>')
+      screen:expect([[
+        ^                                                     |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        :call system("echo")                                 |
+      ]])
+    end)
+
+    it('`yes` and is interrupted with CTRL-C', function()
+      feed(':call system("yes")<cr>')
+      screen:expect([[
+                                                             |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        :call system("yes")                                  |
+      ]])
+      feed('<c-c>')
+      screen:expect([[
+        ^                                                     |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        Type  :quit<Enter>  to exit Nvim                     |
+      ]])
+    end)
+  end)
+
+  describe('passing no input', function()
+    it('returns the program output', function()
+      eq("echoed", eval('system("echo -n echoed")'))
+    end)
+    it('to backgrounded command does not crash', function()
+      -- This is indeterminate, just exercise the codepath.
+      eval('system("echo -n echoed &")')
+      eq(2, eval("1+1"))  -- Still alive?
+    end)
+  end)
+
+  describe('passing input', function()
+    it('returns the program output', function()
+      eq("input", eval('system("cat -", "input")'))
+    end)
+    it('to backgrounded command does not crash', function()
+      -- This is indeterminate, just exercise the codepath.
+      eval('system("cat - &", "input")')
+      eq(2, eval("1+1"))  -- Still alive?
+    end)
+  end)
+
+  describe('passing a lot of input', function()
+    it('returns the program output', function()
+      local input = {}
+      -- write more than 1mb of data, which should be enough to overcome
+      -- the os buffer limit and force multiple event loop iterations to write
+      -- everything
+      for _ = 1, 0xffff do
+        input[#input + 1] = '01234567890ABCDEFabcdef'
+      end
+      input = table.concat(input, '\n')
+      nvim('set_var', 'input', input)
+      eq(input, eval('system("cat -", g:input)'))
+    end)
+  end)
+
+  describe('passing number as input', function()
+    it('stringifies the input', function()
+      eq('1', eval('system("cat", 1)'))
+    end)
+  end)
+
+  describe('with output containing NULs', function()
+    local fname = 'Xtest'
+
+    before_each(create_file_with_nuls(fname))
+    after_each(delete_file(fname))
+
+    it('replaces NULs by SOH characters', function()
+      eq('part1\001part2\001part3\n', eval('system("cat '..fname..'")'))
+    end)
+  end)
+
+  describe('passing list as input', function()
+    it('joins list items with linefeed characters', function()
+      eq('line1\nline2\nline3',
+        eval("system('cat -', ['line1', 'line2', 'line3'])"))
+    end)
+
+    -- Notice that NULs are converted to SOH when the data is read back. This
+    -- is inconsistent and is a good reason for the existence of the
+    -- `systemlist()` function, where input and output map to the same
+    -- characters(see the following tests with `systemlist()` below)
+    describe('with linefeed characters inside list items', function()
+      it('converts linefeed characters to NULs', function()
+        eq('l1\001p2\nline2\001a\001b\nl3',
+          eval([[system('cat -', ["l1\np2", "line2\na\nb", 'l3'])]]))
+      end)
+    end)
+
+    describe('with leading/trailing whitespace characters on items', function()
+      it('preserves whitespace, replacing linefeeds by NULs', function()
+        eq('line \nline2\001\n\001line3',
+          eval([[system('cat -', ['line ', "line2\n", "\nline3"])]]))
+      end)
+    end)
+  end)
+
+  describe("with a program that doesn't close stdout", function()
+    if not xclip then
+      pending('skipped (missing xclip)', function() end)
+    else
+      it('will exit properly after passing input', function()
+        eq('', eval([[system('xclip -i -selection clipboard', 'clip-data')]]))
+        eq('clip-data', eval([[system('xclip -o -selection clipboard')]]))
+      end)
+    end
+  end)
+
+  describe('command passed as a list', function()
+    it('does not execute &shell', function()
+      eq('* $NOTHING ~/file',
+         eval("system(['echo', '-n', '*', '$NOTHING', '~/file'])"))
+    end)
+  end)
+end)
+
+describe('systemlist()', function()
+  -- behavior is similar to `system()` but it returns a list instead of a
+  -- string.
+  before_each(clear)
+
+  it('sets the v:shell_error variable', function()
+    eval([[systemlist("sh -c 'exit'")]])
+    eq(0, eval('v:shell_error'))
+    eval([[systemlist("sh -c 'exit 1'")]])
+    eq(1, eval('v:shell_error'))
+    eval([[systemlist("sh -c 'exit 5'")]])
+    eq(5, eval('v:shell_error'))
+    eval([[systemlist('this-should-not-exist')]])
+    eq(127, eval('v:shell_error'))
+  end)
+
+  describe('exectues shell function', function()
+    local screen
+
+    before_each(function()
+        clear()
+        screen = Screen.new()
+        screen:attach()
+    end)
+
+    after_each(function()
+        screen:detach()
+    end)
+
+    it('`echo` and waits for its return', function()
+      feed(':call systemlist("echo")<cr>')
+      screen:expect([[
+        ^                                                     |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        :call systemlist("echo")                             |
+      ]])
+    end)
+
+    it('`yes` and is interrupted with CTRL-C', function()
+      feed(':call systemlist("yes | xargs")<cr>')
+      screen:expect([[
+                                                             |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        :call systemlist("yes | xargs")                      |
+      ]])
+      feed('<c-c>')
+      screen:expect([[
+        ^                                                     |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        ~                                                    |
+        Type  :quit<Enter>  to exit Nvim                     |
+      ]])
+    end)
+  end)
+
+  describe('passing string with linefeed characters as input', function()
+    it('splits the output on linefeed characters', function()
+      eq({'abc', 'def', 'ghi'}, eval([[systemlist("cat -", "abc\ndef\nghi")]]))
+    end)
+  end)
+
+  describe('passing a lot of input', function()
+    it('returns the program output', function()
+      local input = {}
+      for _ = 1, 0xffff do
+        input[#input + 1] = '01234567890ABCDEFabcdef'
+      end
+      nvim('set_var', 'input', input)
+      eq(input, eval('systemlist("cat -", g:input)'))
+    end)
+  end)
+
+  describe('with output containing NULs', function()
+    local fname = 'Xtest'
+
+    before_each(create_file_with_nuls(fname))
+    after_each(delete_file(fname))
+
+    it('replaces NULs by newline characters', function()
+      eq({'part1\npart2\npart3'}, eval('systemlist("cat '..fname..'")'))
+    end)
+  end)
+
+  describe('passing list as input', function()
+    it('joins list items with linefeed characters', function()
+      eq({'line1', 'line2', 'line3'},
+        eval("systemlist('cat -', ['line1', 'line2', 'line3'])"))
+    end)
+
+    -- Unlike `system()` which uses SOH to represent NULs, with `systemlist()`
+    -- input and ouput are the same
+    describe('with linefeed characters inside list items', function()
+      it('converts linefeed characters to NULs', function()
+        eq({'l1\np2', 'line2\na\nb', 'l3'},
+          eval([[systemlist('cat -', ["l1\np2", "line2\na\nb", 'l3'])]]))
+      end)
+    end)
+
+    describe('with leading/trailing whitespace characters on items', function()
+      it('preserves whitespace, replacing linefeeds by NULs', function()
+        eq({'line ', 'line2\n', '\nline3'},
+          eval([[systemlist('cat -', ['line ', "line2\n", "\nline3"])]]))
+      end)
+    end)
+  end)
+
+  describe('handles empty lines', function()
+    it('in the middle', function()
+      eq({'line one','','line two'}, eval("systemlist('cat',['line one','','line two'])"))
+    end)
+
+    it('in the beginning', function()
+      eq({'','line one','line two'}, eval("systemlist('cat',['','line one','line two'])"))
+    end)
+  end)
+
+  describe('when keepempty option is', function()
+    it('0, ignores trailing newline', function()
+      eq({'aa','bb'}, eval("systemlist('cat',['aa','bb'],0)"))
+      eq({'aa','bb'}, eval("systemlist('cat',['aa','bb',''],0)"))
+    end)
+
+    it('1, preserves trailing newline', function()
+      eq({'aa','bb'}, eval("systemlist('cat',['aa','bb'],1)"))
+      eq({'aa','bb',''}, eval("systemlist('cat',['aa','bb',''],2)"))
+    end)
+  end)
+
+  describe("with a program that doesn't close stdout", function()
+    if not xclip then
+      pending('skipped (missing xclip)', function() end)
+    else
+      it('will exit properly after passing input', function()
+        eq({}, eval(
+          "systemlist('xclip -i -selection clipboard', ['clip', 'data'])"))
+        eq({'clip', 'data'}, eval(
+          "systemlist('xclip -o -selection clipboard')"))
+      end)
+    end
+  end)
+end)