Colorize complete output

If interactive, `complete` commands are highlighted like they would
be if typed. Adds a little fun contrast and it's easier to read.

Moved a function out of fish_indent to highlight.h

src/builtin_complete.cpp

@@ -17,6 +17,8 @@
 #include "parse_constants.h"
 #include "parse_util.h"
 #include "parser.h"
+#include "highlight.h"
+#include "color.h"
 #include "reader.h"
 #include "wgetopt.h"
 #include "wutil.h"  // IWYU pragma: keep
@@ -378,7 +380,17 @@ int builtin_complete(parser_t &parser, io_streams_t &streams, wchar_t **argv) {
     } else if (cmd_to_complete.empty() && path.empty()) {
         // No arguments specified, meaning we print the definitions of all specified completions
         // to stdout.
-        streams.out.append(complete_print());
+        const wcstring repr = complete_print();
+
+        // colorize if interactive
+        if (!streams.out_is_redirected && isatty(STDOUT_FILENO)) {
+            std::vector<highlight_spec_t> colors;
+            size_t len = repr.size();
+            highlight_shell_no_io(repr, colors, len, nullptr, env_stack_t::globals());
+            streams.out.append(str2wcstring(colorize(repr, colors)));
+        } else {
+            streams.out.append(repr);
+        }
     } else {
         int flags = COMPLETE_AUTO_SPACE;
         if (preserve_order) {

src/fish_indent.cpp

@@ -375,26 +375,6 @@ static wcstring prettify(const wcstring &src, bool do_indent) {
     return std::move(prettifier.output);
 }
 
-/// Given a string and list of colors of the same size, return the string with ANSI escape sequences
-/// representing the colors.
-static std::string ansi_colorize(const wcstring &text,
-                                 const std::vector<highlight_spec_t> &colors) {
-    assert(colors.size() == text.size());
-    outputter_t outp;
-
-    highlight_spec_t last_color = highlight_role_t::normal;
-    for (size_t i = 0; i < text.size(); i++) {
-        highlight_spec_t color = colors.at(i);
-        if (color != last_color) {
-            outp.set_color(highlight_get_color(color, false), rgb_color_t::normal());
-            last_color = color;
-        }
-        outp.writech(text.at(i));
-    }
-    outp.set_color(rgb_color_t::normal(), rgb_color_t::normal());
-    return outp.contents();
-}
-
 /// Given a string and list of colors of the same size, return the string with HTML span elements
 /// for the various colors.
 static const wchar_t *html_class_name_for_color(highlight_spec_t spec) {
@@ -676,7 +656,7 @@ int main(int argc, char *argv[]) {
                 break;
             }
             case output_type_ansi: {
-                colored_output = ansi_colorize(output_wtext, colors);
+                colored_output = colorize(output_wtext, colors);
                 break;
             }
             case output_type_html: {

src/highlight.cpp

@@ -1297,6 +1297,25 @@ highlighter_t::color_array_t highlighter_t::highlight() {
     return std::move(color_array);
 }
 
+/// Given a string and list of colors of the same size, return the string with ANSI escape sequences
+/// representing the colors.
+std::string colorize(const wcstring &text, const std::vector<highlight_spec_t> &colors) {
+    assert(colors.size() == text.size());
+    outputter_t outp;
+
+    highlight_spec_t last_color = highlight_role_t::normal;
+    for (size_t i = 0; i < text.size(); i++) {
+        highlight_spec_t color = colors.at(i);
+        if (color != last_color) {
+            outp.set_color(highlight_get_color(color, false), rgb_color_t::normal());
+            last_color = color;
+        }
+        outp.writech(text.at(i));
+    }
+    outp.set_color(rgb_color_t::normal(), rgb_color_t::normal());
+    return outp.contents();
+}
+
 void highlight_shell(const wcstring &buff, std::vector<highlight_spec_t> &color, size_t pos,
                      wcstring_list_t *error, const environment_t &vars) {
     UNUSED(error);

src/highlight.h

@@ -72,6 +72,8 @@ struct highlight_spec_t {
 
 class history_item_t;
 
+std::string colorize(const wcstring &text, const std::vector<highlight_spec_t> &colors);
+
 /// Perform syntax highlighting for the shell commands in buff. The result is stored in the color
 /// array as a color_code from the HIGHLIGHT_ enum for each character in buff.
 ///