Highlight keywords differently

This introduces a new variable $fish_color_keyword that will be used
to highlight keywords. If it's not defined, we fall back on
$fish_color_command as before.

An issue here is that most of our keywords have this weird duality of
also being builtins *if* executed without an argument or with
`--help`.

This means that e.g.

    if

is highlighted as a command until you start typing

    if t

and then it turns keyword.

doc_src/fish_indent_lexer.py

@@ -34,6 +34,7 @@ ROLE_TO_TOKEN = {
     "normal": Name.Variable,
     "error": Generic.Error,
     "command": Name.Function,
+    "keyword": Keyword,
     "statement_terminator": Punctuation,
     "param": Name.Constant,
     "comment": Comment,

doc_src/index.rst

@@ -1398,6 +1398,7 @@ Variable                                                   Meaning
 ==========================================                 =====================================================================
 ``fish_color_normal``                                      default color
 ``fish_color_command``                                     commands like echo
+``fish_color_keyword``                                     keywords like if - this falls back on command color if unset
 ``fish_color_quote``                                       quoted text like "abc"
 ``fish_color_redirection``                                 IO redirections like >/dev/null
 ``fish_color_end``                                         process separators like ';' and '&'

src/fish_indent.cpp

@@ -632,6 +632,7 @@ static const char *highlight_role_to_string(highlight_role_t role) {
         TEST_ROLE(normal)
         TEST_ROLE(error)
         TEST_ROLE(command)
+        TEST_ROLE(keyword)
         TEST_ROLE(statement_terminator)
         TEST_ROLE(param)
         TEST_ROLE(comment)

src/fish_tests.cpp

@@ -4969,7 +4969,7 @@ static void test_highlighting() {
                                {L"&", highlight_role_t::statement_terminator}});
 
     highlight_tests.push_back({
-        {L"command", highlight_role_t::command},
+        {L"command", highlight_role_t::keyword},
         {L"echo", highlight_role_t::command},
         {L"abc", highlight_role_t::param},
         {L"test/fish_highlight_test/foo", param_valid_path},
@@ -4977,14 +4977,15 @@ static void test_highlighting() {
     });
 
     highlight_tests.push_back({
-        {L"if command ls", highlight_role_t::command},
+        {L"if command", highlight_role_t::keyword},
+        {L"ls", highlight_role_t::command},
         {L"; ", highlight_role_t::statement_terminator},
         {L"echo", highlight_role_t::command},
         {L"abc", highlight_role_t::param},
         {L"; ", highlight_role_t::statement_terminator},
         {L"/bin/definitely_not_a_command", highlight_role_t::error},
         {L"; ", highlight_role_t::statement_terminator},
-        {L"end", highlight_role_t::command},
+        {L"end", highlight_role_t::keyword},
     });
 
     // Verify that cd shows errors for non-directories.
@@ -5067,7 +5068,7 @@ static void test_highlighting() {
     highlight_tests.push_back({
         {L"end", highlight_role_t::error},
         {L";", highlight_role_t::statement_terminator},
-        {L"if", highlight_role_t::command},
+        {L"if", highlight_role_t::keyword},
         {L"end", highlight_role_t::error},
     });
 
@@ -5097,12 +5098,12 @@ static void test_highlighting() {
     });
 
     highlight_tests.push_back({
-        {L"for", highlight_role_t::command},
+        {L"for", highlight_role_t::keyword},
         {L"i", highlight_role_t::param},
-        {L"in", highlight_role_t::command},
+        {L"in", highlight_role_t::keyword},
         {L"1 2 3", highlight_role_t::param},
         {L";", highlight_role_t::statement_terminator},
-        {L"end", highlight_role_t::command},
+        {L"end", highlight_role_t::keyword},
     });
 
     highlight_tests.push_back({
@@ -5125,7 +5126,7 @@ static void test_highlighting() {
     });
 
     highlight_tests.push_back({
-        {L"if", highlight_role_t::command},
+        {L"if", highlight_role_t::keyword},
         {L"true", highlight_role_t::command},
         {L"&&", highlight_role_t::operat},
         {L"false", highlight_role_t::command},
@@ -5140,7 +5141,7 @@ static void test_highlighting() {
         {L"!", highlight_role_t::operat},
         {L"true", highlight_role_t::command},
         {L";", highlight_role_t::statement_terminator},
-        {L"end", highlight_role_t::command},
+        {L"end", highlight_role_t::keyword},
     });
 
     highlight_tests.push_back({

src/highlight.cpp

@@ -47,6 +47,8 @@ static const wchar_t *get_highlight_var_name(highlight_role_t role) {
             return L"fish_color_error";
         case highlight_role_t::command:
             return L"fish_color_command";
+        case highlight_role_t::keyword:
+            return L"fish_color_keyword";
         case highlight_role_t::statement_terminator:
             return L"fish_color_end";
         case highlight_role_t::param:
@@ -107,6 +109,8 @@ static highlight_role_t get_fallback(highlight_role_t role) {
             return highlight_role_t::normal;
         case highlight_role_t::command:
             return highlight_role_t::normal;
+        case highlight_role_t::keyword:
+            return highlight_role_t::command;
         case highlight_role_t::statement_terminator:
             return highlight_role_t::normal;
         case highlight_role_t::param:
@@ -949,7 +953,7 @@ void highlighter_t::visit(const ast::keyword_base_t &kw) {
         case parse_keyword_t::kw_in:
         case parse_keyword_t::kw_switch:
         case parse_keyword_t::kw_while:
-            role = highlight_role_t::command;
+            role = highlight_role_t::keyword;
             break;
 
         case parse_keyword_t::kw_and:

src/highlight.h

@@ -17,6 +17,7 @@ enum class highlight_role_t : uint8_t {
     normal = 0,            // normal text
     error,                 // error
     command,               // command
+    keyword,
     statement_terminator,  // process separator
     param,                 // command parameter (argument)
     comment,               // comment