Display the command prompt in error face when the command is not found

Fixes #1021

src/command_manager.cc

@@ -479,7 +479,7 @@ void CommandManager::execute(StringView command_line,
     execute_single_command(params, context, shell_context, command_coord);
 }
 
-CommandInfo CommandManager::command_info(const Context& context, StringView command_line) const
+Optional<CommandInfo> CommandManager::command_info(const Context& context, StringView command_line) const
 {
     TokenList tokens = parse<false>(command_line);
     size_t cmd_idx = 0;
@@ -489,19 +489,19 @@ CommandInfo CommandManager::command_info(const Context& context, StringView comm
             cmd_idx = i+1;
     }
 
-    CommandInfo res;
     if (cmd_idx == tokens.size() or
         (tokens[cmd_idx].type() != Token::Type::Raw and
          tokens[cmd_idx].type() != Token::Type::RawQuoted))
-        return res;
+        return {};
 
     auto cmd = find_command(context, tokens[cmd_idx].content());
     if (cmd == m_commands.end())
-        return res;
+        return {};
 
-    res.first = cmd->first;
+    CommandInfo res;
+    res.name = cmd->first;
     if (not cmd->second.docstring.empty())
-        res.second += cmd->second.docstring + "\n";
+        res.info += cmd->second.docstring + "\n";
 
     if (cmd->second.helper)
     {
@@ -520,7 +520,7 @@ CommandInfo CommandManager::command_info(const Context& context, StringView comm
         {
             if (helpstr.back() != '\n')
                 helpstr += '\n';
-            res.second += helpstr;
+            res.info += helpstr;
         }
     }
 
@@ -528,14 +528,14 @@ CommandInfo CommandManager::command_info(const Context& context, StringView comm
     for (auto& alias : context.aliases().aliases_for(cmd->first))
         aliases += " " + alias;
     if (not aliases.empty())
-        res.second += "Aliases:" + aliases + "\n";
+        res.info += "Aliases:" + aliases + "\n";
 
 
     auto& switches = cmd->second.param_desc.switches;
     if (not switches.empty())
     {
-        res.second += "Switches:\n";
+        res.info += "Switches:\n";
-        res.second += generate_switches_doc(switches);
+        res.info += generate_switches_doc(switches);
     }
 
     return res;

src/command_manager.hh

@@ -8,6 +8,7 @@
 #include "shell_manager.hh"
 #include "parameters_parser.hh"
 #include "string.hh"
+#include "optional.hh"
 #include "utils.hh"
 #include "unordered_map.hh"
 
@@ -38,7 +39,7 @@ enum class CommandFlags
 
 template<> struct WithBitOps<CommandFlags> : std::true_type {};
 
-using CommandInfo = std::pair<String, String>;
+struct CommandInfo { String name, info; };
 
 struct Token
 {
@@ -91,7 +92,7 @@ public:
                          CommandParameters params,
                          size_t token_to_complete, ByteCount pos_in_token);
 
-    CommandInfo command_info(const Context& context,
+    Optional<CommandInfo> command_info(const Context& context,
                                        StringView command_line) const;
 
     bool command_defined(const String& command_name) const;

src/normal.cc

@@ -366,16 +366,21 @@ void command(Context& context, NormalParams params)
             if (context.has_client())
             {
                 context.client().info_hide();
+                if (event == PromptEvent::Change)
+                {
+                    auto info = CommandManager::instance().command_info(context, cmdline);
+                    context.input_handler().set_prompt_face(get_face(info ? "Prompt" : "Error"));
+
                     auto autoinfo = context.options()["autoinfo"].get<AutoInfo>();
-                if (event == PromptEvent::Change and autoinfo & AutoInfo::Command)
+                    if (autoinfo & AutoInfo::Command)
                     {
                         if (cmdline.length() == 1 and is_horizontal_blank(cmdline[0_byte]))
-                        context.client().info_show("prompt", "commands preceded by a blank wont be saved to history",
+                            context.client().info_show("prompt",
+                                                       "commands preceded by a blank wont be saved to history",
                                                        {}, InfoStyle::Prompt);
-
+                        else if (info and not info->info.empty())
-                    auto info = CommandManager::instance().command_info(context, cmdline);
+                            context.client().info_show(info->name, info->info, {}, InfoStyle::Prompt);
-                    if (not info.first.empty() and not info.second.empty())
+                    }
-                        context.client().info_show(info.first, info.second, {}, InfoStyle::Prompt);
                 }
             }
             if (event == PromptEvent::Validate)