vim-patch:9.0.2025: no cmdline completion for ++opt args (#25657)

Problem:  no cmdline completion for ++opt args
Solution: Add cmdline completion for :e ++opt=arg and :terminal
          [++options]

closes: vim/vim#13319

https://github.com/vim/vim/commit/989426be6e9ae23d2413943890206cbe15d9df38

Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>

6 files changed, 176 insertions, 8 deletions

diff --git a/runtime/doc/cmdline.txt b/runtime/doc/cmdline.txt
index 1a5ad9a382..291286d8f7 100644
--- a/runtime/doc/cmdline.txt
+++ b/runtime/doc/cmdline.txt
@@ -364,6 +364,7 @@ When editing the command-line, a few commands can be used to complete the
 word before the cursor.  This is available for:
 
 - Command names: At the start of the command-line.
+- |++opt| values.
 - Tags: Only after the ":tag" command.
 - File names: Only after a command that accepts a file name or a setting for
   an option that can be set to a file name.  This is called file name
diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index aef471a17b..bf0aa54bdd 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -1567,6 +1567,20 @@ static void set_context_for_wildcard_arg(exarg_T *eap, const char *arg, bool use
   }
 }
 
+/// Set the completion context for the "++opt=arg" argument.  Always returns NULL.
+static const char *set_context_in_argopt(expand_T *xp, const char *arg)
+{
+  char *p = vim_strchr(arg, '=');
+  if (p == NULL) {
+    xp->xp_pattern = (char *)arg;
+  } else {
+    xp->xp_pattern = p + 1;
+  }
+
+  xp->xp_context = EXPAND_ARGOPT;
+  return NULL;
+}
+
 /// Set the completion context for the :filter command. Returns a pointer to the
 /// next command after the :filter command.
 static const char *set_context_in_filter_cmd(expand_T *xp, const char *arg)
@@ -2238,13 +2252,23 @@ static const char *set_one_cmd_context(expand_T *xp, const char *buff)
 
   const char *arg = skipwhite(p);
 
-  // Skip over ++argopt argument
-  if ((ea.argt & EX_ARGOPT) && *arg != NUL && strncmp(arg, "++", 2) == 0) {
-    p = arg;
-    while (*p && !ascii_isspace(*p)) {
-      MB_PTR_ADV(p);
+  // Does command allow "++argopt" argument?
+  if (ea.argt & EX_ARGOPT) {
+    while (*arg != NUL && strncmp(arg, "++", 2) == 0) {
+      p = arg + 2;
+      while (*p && !ascii_isspace(*p)) {
+        MB_PTR_ADV(p);
+      }
+
+      // Still touching the command after "++"?
+      if (*p == NUL) {
+        if (ea.argt & EX_ARGOPT) {
+          return set_context_in_argopt(xp, arg + 2);
+        }
+      }
+
+      arg = skipwhite(p);
     }
-    arg = skipwhite(p);
   }
 
   if (ea.cmdidx == CMD_write || ea.cmdidx == CMD_update) {
@@ -2786,6 +2810,8 @@ static int ExpandFromContext(expand_T *xp, char *pat, char ***matches, int *numM
     ret = ExpandSettingSubtract(xp, &regmatch, numMatches, matches);
   } else if (xp->xp_context == EXPAND_MAPPINGS) {
     ret = ExpandMappings(pat, &regmatch, numMatches, matches);
+  } else if (xp->xp_context == EXPAND_ARGOPT) {
+    ret = expand_argopt(pat, xp, &regmatch, matches, numMatches);
   } else if (xp->xp_context == EXPAND_USER_DEFINED) {
     ret = ExpandUserDefined(pat, xp, &regmatch, matches, numMatches);
   } else {
@@ -2883,7 +2909,8 @@ void ExpandGeneric(const char *const pat, expand_T *xp, regmatch_T *regmatch, ch
                             && xp->xp_context != EXPAND_MENUNAMES
                             && xp->xp_context != EXPAND_STRING_SETTING
                             && xp->xp_context != EXPAND_MENUS
-                            && xp->xp_context != EXPAND_SCRIPTNAMES;
+                            && xp->xp_context != EXPAND_SCRIPTNAMES
+                            && xp->xp_context != EXPAND_ARGOPT;
 
   // <SNR> functions should be sorted to the end.
   const bool funcsort = xp->xp_context == EXPAND_EXPRESSION
diff --git a/src/nvim/cmdexpand_defs.h b/src/nvim/cmdexpand_defs.h
index 7c422aca18..0e830a016f 100644
--- a/src/nvim/cmdexpand_defs.h
+++ b/src/nvim/cmdexpand_defs.h
@@ -17,7 +17,8 @@ enum { EXPAND_BUF_LEN = 256, };
 
 /// used for completion on the command line
 typedef struct expand {
-  char *xp_pattern;             ///< start of item to expand
+  char *xp_pattern;             ///< start of item to expand, guaranteed
+                                ///< to be part of xp_line
   int xp_context;               ///< type of expansion
   size_t xp_pattern_len;        ///< bytes in xp_pattern before cursor
   xp_prefix_T xp_prefix;
@@ -104,6 +105,7 @@ enum {
   EXPAND_RUNTIME,
   EXPAND_STRING_SETTING,
   EXPAND_SETTING_SUBTRACT,
+  EXPAND_ARGOPT,
   EXPAND_CHECKHEALTH,
   EXPAND_LUA,
 };
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 279d14f001..664b06108a 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -4087,6 +4087,22 @@ int get_bad_opt(const char *p, exarg_T *eap)
   return OK;
 }
 
+/// Function given to ExpandGeneric() to obtain the list of bad= names.
+static char *get_bad_name(expand_T *xp FUNC_ATTR_UNUSED, int idx)
+{
+  // Note: Keep this in sync with get_bad_opt().
+  static char *(p_bad_values[]) = {
+    "?",
+    "keep",
+    "drop",
+  };
+
+  if (idx < (int)ARRAY_SIZE(p_bad_values)) {
+    return p_bad_values[idx];
+  }
+  return NULL;
+}
+
 /// Get "++opt=arg" argument.
 ///
 /// @return  FAIL or OK.
@@ -4096,6 +4112,8 @@ static int getargopt(exarg_T *eap)
   int *pp = NULL;
   int bad_char_idx;
 
+  // Note: Keep this in sync with get_argopt_name.
+
   // ":edit ++[no]bin[ary] file"
   if (strncmp(arg, "bin", 3) == 0 || strncmp(arg, "nobin", 5) == 0) {
     if (*arg == 'n') {
@@ -4174,6 +4192,70 @@ static int getargopt(exarg_T *eap)
   return OK;
 }
 
+/// Function given to ExpandGeneric() to obtain the list of ++opt names.
+static char *get_argopt_name(expand_T *xp FUNC_ATTR_UNUSED, int idx)
+{
+  // Note: Keep this in sync with getargopt().
+  static char *(p_opt_values[]) = {
+    "fileformat=",
+    "encoding=",
+    "binary",
+    "nobinary",
+    "bad=",
+    "edit",
+    "p",
+  };
+
+  if (idx < (int)ARRAY_SIZE(p_opt_values)) {
+    return p_opt_values[idx];
+  }
+  return NULL;
+}
+
+/// Command-line expansion for ++opt=name.
+int expand_argopt(char *pat, expand_T *xp, regmatch_T *rmp, char ***matches, int *numMatches)
+{
+  if (xp->xp_pattern > xp->xp_line && *(xp->xp_pattern - 1) == '=') {
+    CompleteListItemGetter cb = NULL;
+
+    char *name_end = xp->xp_pattern - 1;
+    if (name_end - xp->xp_line >= 2
+        && strncmp(name_end - 2, "ff", 2) == 0) {
+      cb = get_fileformat_name;
+    } else if (name_end - xp->xp_line >= 10
+               && strncmp(name_end - 10, "fileformat", 10) == 0) {
+      cb = get_fileformat_name;
+    } else if (name_end - xp->xp_line >= 3
+               && strncmp(name_end - 3, "enc", 3) == 0) {
+      cb = get_encoding_name;
+    } else if (name_end - xp->xp_line >= 8
+               && strncmp(name_end - 8, "encoding", 8) == 0) {
+      cb = get_encoding_name;
+    } else if (name_end - xp->xp_line >= 3
+               && strncmp(name_end - 3, "bad", 3) == 0) {
+      cb = get_bad_name;
+    }
+
+    if (cb != NULL) {
+      ExpandGeneric(pat, xp, rmp, matches, numMatches, cb, false);
+      return OK;
+    }
+    return FAIL;
+  }
+
+  // Special handling of "ff" which acts as a short form of
+  // "fileformat", as "ff" is not a substring of it.
+  if (strcmp(xp->xp_pattern, "ff") == 0) {
+    *matches = xmalloc(sizeof(char *));
+    *numMatches = 1;
+    (*matches)[0] = xstrdup("fileformat=");
+    return OK;
+  }
+
+  ExpandGeneric(pat, xp, rmp, matches, numMatches, get_argopt_name, false);
+  return OK;
+}
+
 /// Handle the argument for a tabpage related ex command.
 /// When an error is encountered then eap->errmsg is set.
 ///
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index 6f41bba99b..88e7ebd991 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -1490,6 +1490,17 @@ int expand_set_fileformat(optexpand_T *args, int *numMatches, char ***matches)
                                matches);
 }
 
+/// Function given to ExpandGeneric() to obtain the possible arguments of the
+/// fileformat options.
+char *get_fileformat_name(expand_T *xp FUNC_ATTR_UNUSED, int idx)
+{
+  if (idx >= (int)ARRAY_SIZE(p_ff_values)) {
+    return NULL;
+  }
+
+  return p_ff_values[idx];
+}
+
 /// The 'fileformats' option is changed.
 const char *did_set_fileformats(optset_T *args)
 {
diff --git a/test/old/testdir/test_cmdline.vim b/test/old/testdir/test_cmdline.vim
index 90748a6076..00c894058e 100644
--- a/test/old/testdir/test_cmdline.vim
+++ b/test/old/testdir/test_cmdline.vim
@@ -1039,6 +1039,51 @@ func Test_cmdline_complete_expression()
   unlet g:SomeVar
 endfunc
 
+func Test_cmdline_complete_argopt()
+  " completion for ++opt=arg for file commands
+  call assert_equal('fileformat=', getcompletion('edit ++', 'cmdline')[0])
+  call assert_equal('encoding=', getcompletion('read ++e', 'cmdline')[0])
+  call assert_equal('edit', getcompletion('read ++bin ++edi', 'cmdline')[0])
+
+  call assert_equal(['fileformat='], getcompletion('edit ++ff', 'cmdline'))
+
+  call assert_equal('dos', getcompletion('write ++ff=d', 'cmdline')[0])
+  call assert_equal('mac', getcompletion('args ++fileformat=m', 'cmdline')[0])
+  call assert_equal('utf-8', getcompletion('split ++enc=ut*-8', 'cmdline')[0])
+  call assert_equal('latin1', getcompletion('tabedit ++encoding=lati', 'cmdline')[0])
+  call assert_equal('keep', getcompletion('edit ++bad=k', 'cmdline')[0])
+
+  call assert_equal([], getcompletion('edit ++bogus=', 'cmdline'))
+
+  " completion should skip the ++opt and continue
+  call writefile([], 'Xaaaaa.txt', 'D')
+  call feedkeys(":split ++enc=latin1 Xaaa\<C-A>\<C-B>\"\<CR>", 'xt')
+  call assert_equal('"split ++enc=latin1 Xaaaaa.txt', @:)
+
+  if has('terminal')
+    " completion for terminal's [options]
+    call assert_equal('close', getcompletion('terminal ++cl*e', 'cmdline')[0])
+    call assert_equal('hidden', getcompletion('terminal ++open ++hidd', 'cmdline')[0])
+    call assert_equal('term', getcompletion('terminal ++kill=ter', 'cmdline')[0])
+
+    call assert_equal([], getcompletion('terminal ++bogus=', 'cmdline'))
+
+    " :terminal completion should skip the ++opt when considering what is the
+    " first option, which is a list of shell commands, unlike second option
+    " onwards.
+    let first_param = getcompletion('terminal ', 'cmdline')
+    let second_param = getcompletion('terminal foo ', 'cmdline')
+    let skipped_opt_param = getcompletion('terminal ++close ', 'cmdline')
+    call assert_equal(first_param, skipped_opt_param)
+    call assert_notequal(first_param, second_param)
+  endif
+endfunc
+
+" Unique function name for completion below
+func s:WeirdFunc()
+  echo 'weird'
+endfunc
+
 " Test for various command-line completion
 func Test_cmdline_complete_various()
   " completion for a command starting with a comment