zsh completion with help

TABCOMPLETION.md

@@ -14,11 +14,31 @@ eval "$(register-python-argcomplete build.py)"
 eval "$(register-python-argcomplete translate.py)"
 
 function _downward_complete() {
-    local IFS=$'\n'
-    COMPREPLY=( $( "$1" --bash-complete \
-                   "$COMP_POINT" "$COMP_LINE" "$COMP_CWORD" ${COMP_WORDS[@]}))
+    local IFS=$'\013'
+    if [[ -n "${ZSH_VERSION-}" ]]; then
+        local DFS=":"
+        local completions
+        local COMP_CWORD=$((CURRENT - 1))
+        completions=( $( "${words[1]}" --bash-complete \
+                         "$IFS" "$DFS" "$CURSOR" "$BUFFER" "$COMP_CWORD" ${words[@]}))
+        if [[ $? == 0 ]]; then
+            _describe "${words[1]}" completions -o nosort
+        fi
+    else
+        local DFS=""
+        COMPREPLY=( $( "$1" --bash-complete \
+                    "$IFS" "$DFS" "$COMP_POINT" "$COMP_LINE" "$COMP_CWORD" ${COMP_WORDS[@]}))
+        if [[ $? != 0 ]]; then
+            unset COMPREPLY
+        fi
+    fi
 }
-complete -o nosort -o default -o bashdefault -F _downward_complete downward
+
+if [[ -n "${ZSH_VERSION-}" ]]; then
+    compdef _downward_complete downward
+else
+    complete -o nosort -F _downward_complete downward
+fi
 ```
 
 Restart your shell afterwards.

driver/tab_completion.py

@@ -122,15 +122,16 @@ def _call_argcomplete(python_file, comp_line, comp_point):
         return _split_argcomplete_ouput(f.read(), entry_separator, help_separator)
 
 def _get_completions_from_downward(downward, options, prefix):
-    # TODO: entry_separator, help_separator = _get_field_separators(os.environ)
+    entry_separator, help_separator = _get_field_separators(os.environ)
+    help_separator = help_separator or ":"
     simulated_commandline = [str(downward)] + options + [prefix]
     comp_line = " ".join(simulated_commandline)
     comp_point = str(len(comp_line))
     comp_cword = str(len(simulated_commandline) - 1)
-    cmd = [str(downward), "--bash-complete", # TODO: "--ifs", entry_separator, "--dfs", help_separator,
+    cmd = [str(downward), "--bash-complete", entry_separator, help_separator,
            comp_point, comp_line, comp_cword] + simulated_commandline
     output = subprocess.check_output(cmd, text=True)
-    return _split_argcomplete_ouput(output, "\n", ":") # TODO: entry_separator, help_separator)
+    return _split_argcomplete_ouput(output, entry_separator, help_separator)
 
 
 def _get_completions_from_translator(translator, options, prefix):

src/search/command_line.cc

@@ -184,18 +184,18 @@ shared_ptr<SearchAlgorithm> parse_cmd_line(
     return parse_cmd_line_aux(args);
 }
 
-static vector<string> complete_args(
+static vector<pair<string, string>> complete_args(
     const vector<string> &parsed_args, const string &current_word,
     int cursor_pos) {
     string prefix = current_word.substr(0, cursor_pos);
     assert(!parsed_args.empty()); // args[0] is always the program name.
     const string &last_arg = parsed_args.back();
-    vector<string> suggestions;
+    vector<pair<string, string>> suggestions;
     if (find(parsed_args.begin(), parsed_args.end(), "--help") != parsed_args.end()) {
-        suggestions.push_back("--txt2tags");
+        suggestions.emplace_back("--txt2tags", "");
         plugins::Registry registry = plugins::RawRegistry::instance()->construct_registry();
         for (const shared_ptr<const plugins::Feature> &feature : registry.get_features()) {
-            suggestions.push_back(feature->get_key());
+            suggestions.emplace_back(feature->get_key(), feature->get_title());
         }
     } else if (last_arg == "--internal-plan-file") {
         /* Suggest filename starting with current_word.
@@ -210,22 +210,22 @@ static vector<string> complete_args(
         exit(1);
     } else {
         // not completing an argument
-        suggestions.push_back("--help");
-        suggestions.push_back("--search");
-        suggestions.push_back("--internal-plan-file");
-        suggestions.push_back("--internal-previous-portfolio-plans");
-        suggestions.push_back("--if-unit-cost");
-        suggestions.push_back("--if-non-unit-cost");
-        suggestions.push_back("--always");
+        suggestions.emplace_back("--help", "");
+        suggestions.emplace_back("--search", "");
+        suggestions.emplace_back("--internal-plan-file", "");
+        suggestions.emplace_back("--internal-previous-portfolio-plans", "");
+        suggestions.emplace_back("--if-unit-cost", "");
+        suggestions.emplace_back("--if-non-unit-cost", "");
+        suggestions.emplace_back("--always", "");
         // remove suggestions not starting with current_word
     }
 
     if (!current_word.empty()) {
         // Suggest only words that match with current_word
         suggestions.erase(
             remove_if(suggestions.begin(), suggestions.end(),
-                      [&](const string &value) {
-                          return !value.starts_with(current_word);
+                      [&](const pair<string, string> &value) {
+                          return !value.first.starts_with(current_word);
                       }), suggestions.end());
     }
     return suggestions;
@@ -279,23 +279,27 @@ void handle_tab_completion(int argc, const char **argv) {
     if (argc < 2 || string(argv[1]) != "--bash-complete") {
         return;
     }
-    if (argc < 5) {
+    if (argc < 7) {
         input_error(
             "The option --bash-complete is only meant to be called "
             "internally to generate suggestions for tab completion.\n"
-            "Usage:\n    ./downward --bash-complete "
+            "Usage:\n    ./downward --bash-complete $IFS $DFS\n"
             "$COMP_POINT \"$COMP_LINE\" $COMP_CWORD ${COMP_WORDS[@]}\n"
             "where the environment variables have their usual meaning for bash completion:\n"
+            "$IFS is a character used to separate different suggestions.\n"
+            "$DFS is a character used within a suggestion to separate the value from its description.\n"
             "$COMP_POINT is the position of the cursor in the command line.\n"
             "$COMP_LINE is the current command line.\n"
             "$COMP_CWORD is an index into ${COMP_WORDS} of the word under the cursor.\n"
             "$COMP_WORDS is the current command line split into words.\n"
             );
     }
-    int cursor_pos = parse_int_arg("COMP_POINT", argv[2]);
-    string command_line(argv[3]);
-    int cursor_word_index = parse_int_arg("COMP_CWORD", argv[4]);
-    vector<string> words(&argv[5], &argv[argc]);
+    string entry_separator(argv[2]);
+    string help_separator(argv[3]);
+    int cursor_pos = parse_int_arg("COMP_POINT", argv[4]);
+    string command_line(argv[5]);
+    int cursor_word_index = parse_int_arg("COMP_CWORD", argv[6]);
+    vector<string> words(&argv[7], &argv[argc]);
     // Sentinel for cases where the cursor is after the last word.
     words.push_back("");
 
@@ -309,8 +313,13 @@ void handle_tab_completion(int argc, const char **argv) {
     int pos_in_word = get_position_in_current_word(
         cursor_word_index, command_line, cursor_pos, words);
 
-    for (const string &suggestion : complete_args(preceding_words, current_word, pos_in_word)) {
-        cout << suggestion << endl;
+    for (const auto &[suggestion, description] : complete_args(
+        preceding_words, current_word, pos_in_word)) {
+        cout << suggestion;
+        if (!description.empty() && !help_separator.empty()) {
+            cout << help_separator << description;
+        }
+        cout << entry_separator;
     }
     // Do not use exit_with here because it would generate additional output.
     exit(0);