refactor(tests): remove redir_exec #15718

Problem
- `redir_exec` is obsolete, but it keeps getting used in new tests
  because people copy existing tests.
- Disadvantages of `redir_exec`:
  - Captures extra junk before the actual error/message that we _want_ to test.
  - Does not fail on error, unlike e.g. `command()`.

Solution
- Use new functions like `nvim_exec` and `pcall_err`.

2 files changed, 19 insertions, 29 deletions

diff --git a/test/functional/ex_cmds/echo_spec.lua b/test/functional/ex_cmds/echo_spec.lua
index 404dc39ad2..d320425de1 100644
--- a/test/functional/ex_cmds/echo_spec.lua
+++ b/test/functional/ex_cmds/echo_spec.lua
@@ -10,7 +10,7 @@ local source = helpers.source
 local dedent = helpers.dedent
 local command = helpers.command
 local exc_exec = helpers.exc_exec
-local redir_exec = helpers.redir_exec
+local exec_capture = helpers.exec_capture
 local matches = helpers.matches
 
 describe(':echo :echon :echomsg :echoerr', function()
@@ -199,10 +199,8 @@ describe(':echo :echon :echomsg :echoerr', function()
         let d.tdr = TestDictRef
       ]])
       eq(dedent([[
-
-          function('TestDict', {'tdr': function('TestDict', {...@1})})
           function('TestDict', {'tdr': function('TestDict', {...@1})})]]),
-         redir_exec('echo String(d.tdr)'))
+         exec_capture('echo String(d.tdr)'))
     end)
 
     it('dumps automatically created partials', function()
@@ -229,10 +227,8 @@ describe(':echo :echon :echomsg :echoerr', function()
     function()
       meths.set_var('d', {v=true})
       eq(dedent([[
-
-          {'p': function('<SNR>2_Test2', {...@0}), 'f': function('<SNR>2_Test2'), 'v': v:true}
           {'p': function('<SNR>2_Test2', {...@0}), 'f': function('<SNR>2_Test2'), 'v': v:true}]]),
-        redir_exec('echo String(extend(extend(g:d, {"f": g:Test2_f}), {"p": g:d.f}))'))
+        exec_capture('echo String(extend(extend(g:d, {"f": g:Test2_f}), {"p": g:d.f}))'))
     end)
 
     it('does not show errors when dumping partials referencing the same dictionary',
@@ -256,10 +252,8 @@ describe(':echo :echon :echomsg :echoerr', function()
       -- test/unit/api/private_helpers_spec.lua.
       eval('add(l, function("Test1", l))')
       eq(dedent([=[
-
-          function('Test1', [[[...@2], function('Test1', [[...@2]])], function('Test1', [[[...@4], function('Test1', [[...@4]])]])])
           function('Test1', [[[...@2], function('Test1', [[...@2]])], function('Test1', [[[...@4], function('Test1', [[...@4]])]])])]=]),
-        redir_exec('echo String(function("Test1", l))'))
+        exec_capture('echo String(function("Test1", l))'))
     end)
 
     it('does not crash or halt when dumping partials with reference cycles in self and arguments',
@@ -270,10 +264,8 @@ describe(':echo :echon :echomsg :echoerr', function()
       eval('add(l, function("Test1", l))')
       eval('add(l, function("Test1", d))')
       eq(dedent([=[
-
-          {'p': function('<SNR>2_Test2', [[[...@3], function('Test1', [[...@3]]), function('Test1', {...@0})], function('Test1', [[[...@5], function('Test1', [[...@5]]), function('Test1', {...@0})]]), function('Test1', {...@0})], {...@0}), 'f': function('<SNR>2_Test2'), 'v': v:true}
           {'p': function('<SNR>2_Test2', [[[...@3], function('Test1', [[...@3]]), function('Test1', {...@0})], function('Test1', [[[...@5], function('Test1', [[...@5]]), function('Test1', {...@0})]]), function('Test1', {...@0})], {...@0}), 'f': function('<SNR>2_Test2'), 'v': v:true}]=]),
-        redir_exec('echo String(extend(extend(g:d, {"f": g:Test2_f}), {"p": function(g:d.f, l)}))'))
+        exec_capture('echo String(extend(extend(g:d, {"f": g:Test2_f}), {"p": function(g:d.f, l)}))'))
     end)
   end)
 
@@ -303,8 +295,8 @@ describe(':echo :echon :echomsg :echoerr', function()
     it('dumps recursive lists without error', function()
       meths.set_var('l', {})
       eval('add(l, l)')
-      eq('\n[[...@0]]\n[[...@0]]', redir_exec('echo String(l)'))
-      eq('\n[[[...@1]]]\n[[[...@1]]]', redir_exec('echo String([l])'))
+      eq('[[...@0]]', exec_capture('echo String(l)'))
+      eq('[[[...@1]]]', exec_capture('echo String([l])'))
     end)
   end)
 
@@ -333,10 +325,10 @@ describe(':echo :echon :echomsg :echoerr', function()
     it('dumps recursive dictionaries without the error', function()
       meths.set_var('d', {d=1})
       eval('extend(d, {"d": d})')
-      eq('\n{\'d\': {...@0}}\n{\'d\': {...@0}}',
-         redir_exec('echo String(d)'))
-      eq('\n{\'out\': {\'d\': {...@1}}}\n{\'out\': {\'d\': {...@1}}}',
-         redir_exec('echo String({"out": d})'))
+      eq('{\'d\': {...@0}}',
+         exec_capture('echo String(d)'))
+      eq('{\'out\': {\'d\': {...@1}}}',
+         exec_capture('echo String({"out": d})'))
     end)
   end)
 
diff --git a/test/functional/ex_cmds/write_spec.lua b/test/functional/ex_cmds/write_spec.lua
index 4f526ddfca..32fe397c03 100644
--- a/test/functional/ex_cmds/write_spec.lua
+++ b/test/functional/ex_cmds/write_spec.lua
@@ -3,8 +3,7 @@ local lfs = require('lfs')
 local eq, eval, clear, write_file, source, insert =
   helpers.eq, helpers.eval, helpers.clear, helpers.write_file,
   helpers.source, helpers.insert
-local redir_exec = helpers.redir_exec
-local exc_exec = helpers.exc_exec
+local pcall_err = helpers.pcall_err
 local command = helpers.command
 local feed_command = helpers.feed_command
 local funcs = helpers.funcs
@@ -96,25 +95,24 @@ describe(':write', function()
     eq(funcs.fnamemodify('.', ':p:h'), funcs.fnamemodify('.', ':p:h:~'))
     -- Message from check_overwrite
     if not iswin() then
-      eq(('\nE17: "'..funcs.fnamemodify('.', ':p:h')..'" is a directory'),
-        redir_exec('write .'))
+      eq(('Vim(write):E17: "'..funcs.fnamemodify('.', ':p:h')..'" is a directory'),
+        pcall_err(command, 'write .'))
     end
     meths.set_option('writeany', true)
     -- Message from buf_write
-    eq(('\nE502: "." is a directory'),
-       redir_exec('write .'))
+    eq(('Vim(write):E502: "." is a directory'), pcall_err(command, 'write .'))
     funcs.mkdir(fname_bak)
     meths.set_option('backupdir', '.')
     meths.set_option('backup', true)
     write_file(fname, 'content0')
-    eq(0, exc_exec('edit ' .. fname))
+    command('edit ' .. fname)
     funcs.setline(1, 'TTY')
     eq('Vim(write):E510: Can\'t make backup file (add ! to override)',
-       exc_exec('write'))
+       pcall_err(command, 'write'))
     meths.set_option('backup', false)
     funcs.setfperm(fname, 'r--------')
     eq('Vim(write):E505: "Xtest-functional-ex_cmds-write" is read-only (add ! to override)',
-       exc_exec('write'))
+       pcall_err(command, 'write'))
     if iswin() then
       eq(0, os.execute('del /q/f ' .. fname))
       eq(0, os.execute('rd /q/s ' .. fname_bak))
@@ -127,6 +125,6 @@ describe(':write', function()
     if iswin() then return end
     lfs.link(fname_bak .. ('/xxxxx'):rep(20), fname, true)
     eq('Vim(write):E166: Can\'t open linked file for writing',
-       exc_exec('write!'))
+       pcall_err(command, 'write!'))
   end)
 end)