feat(ftplugin): change 'commentstring' to `// %s` for C/C++ (#29085)

Problem: The default commentstring for C/C++ can lead to invalid code 
when commenting and does not match the Nvim codebase.

Solution: Change commentstring to `// %s` as used by Neovim. Also
set all commentstrings that derive from the default C string explicitly
(and correctly).

12 files changed, 12 insertions, 8 deletions

diff --git a/runtime/ftplugin/arduino.lua b/runtime/ftplugin/arduino.lua
new file mode 100644
index 0000000000..f398d66a63
--- /dev/null
+++ b/runtime/ftplugin/arduino.lua
@@ -0,0 +1 @@
+vim.bo.commentstring = '// %s'
diff --git a/runtime/ftplugin/c.lua b/runtime/ftplugin/c.lua
index 0ddbf09470..2695b642aa 100644
--- a/runtime/ftplugin/c.lua
+++ b/runtime/ftplugin/c.lua
@@ -1,5 +1,5 @@
 -- These are the default option values in Vim, but not in Nvim, so must be set explicitly.
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '// %s'
 vim.bo.define = '^\\s*#\\s*define'
 vim.bo.include = '^\\s*#\\s*include'
 
diff --git a/runtime/ftplugin/calender.lua b/runtime/ftplugin/calender.lua
index b4e68148f5..984111a08b 100644
--- a/runtime/ftplugin/calender.lua
+++ b/runtime/ftplugin/calender.lua
@@ -1 +1 @@
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '/* %s */'
diff --git a/runtime/ftplugin/ch.lua b/runtime/ftplugin/ch.lua
new file mode 100644
index 0000000000..f398d66a63
--- /dev/null
+++ b/runtime/ftplugin/ch.lua
@@ -0,0 +1 @@
+vim.bo.commentstring = '// %s'
diff --git a/runtime/ftplugin/cs.lua b/runtime/ftplugin/cs.lua
index b4e68148f5..f398d66a63 100644
--- a/runtime/ftplugin/cs.lua
+++ b/runtime/ftplugin/cs.lua
@@ -1 +1 @@
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '// %s'
diff --git a/runtime/ftplugin/css.lua b/runtime/ftplugin/css.lua
index b4e68148f5..984111a08b 100644
--- a/runtime/ftplugin/css.lua
+++ b/runtime/ftplugin/css.lua
@@ -1 +1 @@
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '/* %s */'
diff --git a/runtime/ftplugin/d.lua b/runtime/ftplugin/d.lua
index b4e68148f5..f398d66a63 100644
--- a/runtime/ftplugin/d.lua
+++ b/runtime/ftplugin/d.lua
@@ -1 +1 @@
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '// %s'
diff --git a/runtime/ftplugin/indent.lua b/runtime/ftplugin/indent.lua
index b4e68148f5..f398d66a63 100644
--- a/runtime/ftplugin/indent.lua
+++ b/runtime/ftplugin/indent.lua
@@ -1 +1 @@
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '// %s'
diff --git a/runtime/ftplugin/objc.lua b/runtime/ftplugin/objc.lua
new file mode 100644
index 0000000000..f398d66a63
--- /dev/null
+++ b/runtime/ftplugin/objc.lua
@@ -0,0 +1 @@
+vim.bo.commentstring = '// %s'
diff --git a/runtime/ftplugin/xdefaults.lua b/runtime/ftplugin/xdefaults.lua
index b4e68148f5..e54bf808b0 100644
--- a/runtime/ftplugin/xdefaults.lua
+++ b/runtime/ftplugin/xdefaults.lua
@@ -1 +1 @@
-vim.bo.commentstring = '/*%s*/'
+vim.bo.commentstring = '! %s'
diff --git a/runtime/ftplugin/xs.lua b/runtime/ftplugin/xs.lua
new file mode 100644
index 0000000000..f398d66a63
--- /dev/null
+++ b/runtime/ftplugin/xs.lua
@@ -0,0 +1 @@
+vim.bo.commentstring = '// %s'
diff --git a/test/functional/lua/runtime_spec.lua b/test/functional/lua/runtime_spec.lua
index c6b0577ebe..f63363d6d9 100644
--- a/test/functional/lua/runtime_spec.lua
+++ b/test/functional/lua/runtime_spec.lua
@@ -406,7 +406,7 @@ describe('runtime:', function()
     eq('', eval('&commentstring'))
     eq('', eval('&omnifunc'))
     exec('edit file.cpp')
-    eq('/*%s*/', eval('&commentstring'))
+    eq('// %s', eval('&commentstring'))
     eq('ccomplete#Complete', eval('&omnifunc'))
   end)
 end)