eval: executable(), exepath() accept strings only

Cherry-pick f_executable(), f_exepath(), check_for_string() from patch 8.2.2117.
Rename check_for_string() to tv_check_for_string().
https://github.com/vim/vim/commit/7bb4e74c38642682cfdd0cb4052adfa5efdd7dd1

Close https://github.com/neovim/neovim/issues/13485

8 files changed, 32 insertions, 7 deletions

diff --git a/test/functional/eval/executable_spec.lua b/test/functional/eval/executable_spec.lua
index a1cf056907..f8e579a8ff 100644
--- a/test/functional/eval/executable_spec.lua
+++ b/test/functional/eval/executable_spec.lua
@@ -2,6 +2,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local eq, clear, call, iswin, write_file, command =
   helpers.eq, helpers.clear, helpers.call, helpers.iswin, helpers.write_file,
   helpers.command
+local exc_exec = helpers.exc_exec
 local eval = helpers.eval
 
 describe('executable()', function()
@@ -12,6 +13,16 @@ describe('executable()', function()
     eq(1, call('executable', exe))
   end)
 
+  it('fails for invalid values', function()
+    for _, input in ipairs({'""', 'v:null', 'v:true', 'v:false', '{}', '[]'}) do
+      eq('Vim(call):E928: String required', exc_exec('call executable('..input..')'))
+    end
+    command('let $PATH = fnamemodify("./test/functional/fixtures/bin", ":p")')
+    for _, input in ipairs({'v:null', 'v:true', 'v:false'}) do
+      eq('Vim(call):E928: String required', exc_exec('call executable('..input..')'))
+    end
+  end)
+
   it('returns 0 for non-existent files', function()
     eq(0, call('executable', 'no_such_file_exists_209ufq23f'))
   end)
diff --git a/test/functional/eval/exepath_spec.lua b/test/functional/eval/exepath_spec.lua
index 10a11aeacc..b86fea5535 100644
--- a/test/functional/eval/exepath_spec.lua
+++ b/test/functional/eval/exepath_spec.lua
@@ -1,14 +1,28 @@
 local helpers = require('test.functional.helpers')(after_each)
 local eq, clear, call, iswin =
   helpers.eq, helpers.clear, helpers.call, helpers.iswin
+local command = helpers.command
+local exc_exec = helpers.exc_exec
 
-describe('exepath() (Windows)', function()
-  if not iswin() then return end  -- N/A for Unix.
+describe('exepath()', function()
+  before_each(clear)
 
-  it('append extension if omitted', function()
-    local filename = 'cmd'
-    local pathext = '.exe'
-    clear({env={PATHEXT=pathext}})
-    eq(call('exepath', filename..pathext), call('exepath', filename))
+  it('fails for invalid values', function()
+    for _, input in ipairs({'""', 'v:null', 'v:true', 'v:false', '{}', '[]'}) do
+      eq('Vim(call):E928: String required', exc_exec('call exepath('..input..')'))
+    end
+    command('let $PATH = fnamemodify("./test/functional/fixtures/bin", ":p")')
+    for _, input in ipairs({'v:null', 'v:true', 'v:false'}) do
+      eq('Vim(call):E928: String required', exc_exec('call exepath('..input..')'))
+    end
   end)
+
+  if iswin() then
+    it('append extension if omitted', function()
+      local filename = 'cmd'
+      local pathext = '.exe'
+      clear({env={PATHEXT=pathext}})
+      eq(call('exepath', filename..pathext), call('exepath', filename))
+    end)
+  end
 end)
diff --git a/test/functional/fixtures/bin/false b/test/functional/fixtures/bin/false
new file mode 100755
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/functional/fixtures/bin/false
diff --git a/test/functional/fixtures/bin/false.cmd b/test/functional/fixtures/bin/false.cmd
new file mode 100755
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/functional/fixtures/bin/false.cmd
diff --git a/test/functional/fixtures/bin/null b/test/functional/fixtures/bin/null
new file mode 100755
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/functional/fixtures/bin/null
diff --git a/test/functional/fixtures/bin/null.cmd b/test/functional/fixtures/bin/null.cmd
new file mode 100755
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/functional/fixtures/bin/null.cmd
diff --git a/test/functional/fixtures/bin/true b/test/functional/fixtures/bin/true
new file mode 100755
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/functional/fixtures/bin/true
diff --git a/test/functional/fixtures/bin/true.cmd b/test/functional/fixtures/bin/true.cmd
new file mode 100755
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/functional/fixtures/bin/true.cmd