Also check shell parameters for kak_* references

This makes it easier to pass shell fragments as arguments so that
%sh{ eval "$@" } just works even if arguments refer to Kakoune's
vars.

doc/pages/changelog.asciidoc

@@ -3,6 +3,10 @@
 This changelog contains major and/or breaking changes to Kakoune between
 released versions.
 
+== Development version
+
+* Expose env vars that are mentionned in the arguments passed to shell expansions
+
 == Kakoune 2024.05.18
 
 * Fixed tests on Alpine Linux and *BSD

doc/pages/expansions.asciidoc

@@ -146,14 +146,16 @@ and unquote them, then execute the resulting `set` command, which sets
 the shell's argument variables to the items from `$kak_selections`. The
 `while` loop with `shift` iterates through the arguments one by one.
 
-Only variables actually mentioned in the body of the shell expansion will
-be exported into the shell's environment. For example:
+Only variables actually mentioned in the body of the shell expansion or
+in passed arguments will be exported into the shell's environment.
+
+For example:
 
 ----
 echo %sh{ env | grep ^kak_ }
 ----
 
-... will find none of Kakoune's special environment variables, but:
+... will not find any of Kakoune's special environment variables, but:
 
 ----
 echo %sh{ env | grep ^kak_ # kak_session }
@@ -162,6 +164,15 @@ echo %sh{ env | grep ^kak_ # kak_session }
 ... will find the `$kak_session` variable because it was mentioned by name
 in a comment, even though it wasn't directly used.
 
+----
+define-command -params .. eval-shell %{ echo %sh{ eval "$@" } }
+eval-shell 'echo $kak_session'
+----
+
+... will also find the `$kak_session` variable because it was mentioned by name
+in the command arguments, which are automatically made available to shell blocks
+as "$@"
+
 TIP: These environment variables are also available in other contexts where
 Kakoune uses a shell command, such as the `|`, `!` or `$` normal mode commands
 (See <<keys#,`:doc keys`>>).

src/main.cc

@@ -45,6 +45,9 @@ struct {
     unsigned int version;
     StringView notes;
 } constexpr version_notes[] = { {
+        0,
+        "» kak_* appearing in shell arguments will be added to the environment\n"
+    }, {
         20240518,
         "» Fix tests failing on some platforms\n"
     }, {

src/shell_manager.cc

@@ -141,30 +141,35 @@ Shell spawn_shell(const char* shell, StringView cmdline,
 }
 
 template<typename GetValue>
-Vector<String> generate_env(StringView cmdline, const Context& context, GetValue&& get_value)
+Vector<String> generate_env(StringView cmdline, ConstArrayView<String> params, const Context& context, GetValue&& get_value)
 {
     static const Regex re(R"(\bkak_(quoted_)?(\w+)\b)");
 
     Vector<String> env;
-    for (auto&& match : RegexIterator{cmdline.begin(), cmdline.end(), re})
-    {
-        StringView name{match[2].first, match[2].second};
-        StringView shell_name{match[0].first, match[0].second};
-
-        auto match_name = [&](const String& s) {
-            return s.substr(0_byte, shell_name.length()) == shell_name and
-                   s.substr(shell_name.length(), 1_byte) == "=";
-        };
-        if (any_of(env, match_name))
-            continue;
-
-        try
+    auto add_matches = [&](StringView s) {
+        for (auto&& match : RegexIterator{s.begin(), s.end(), re})
         {
-            StringView quoted{match[1].first, match[1].second};
-            Quoting quoting = match[1].matched ? Quoting::Shell : Quoting::Raw;
-            env.push_back(format("kak_{}{}={}", quoted, name, get_value(name, quoting)));
-        } catch (runtime_error&) {}
-    }
+            StringView name{match[2].first, match[2].second};
+            StringView shell_name{match[0].first, match[0].second};
+
+            auto match_name = [&](const String& s) {
+                return s.substr(0_byte, shell_name.length()) == shell_name and
+                       s.substr(shell_name.length(), 1_byte) == "=";
+            };
+            if (any_of(env, match_name))
+                continue;
+
+            try
+            {
+                StringView quoted{match[1].first, match[1].second};
+                Quoting quoting = match[1].matched ? Quoting::Shell : Quoting::Raw;
+                env.push_back(format("kak_{}{}={}", quoted, name, get_value(name, quoting)));
+            } catch (runtime_error&) {}
+        }
+    };
+    add_matches(cmdline);
+    for (auto&& param : params)
+        add_matches(param);
 
     return env;
 }
@@ -265,13 +270,13 @@ std::pair<String, int> ShellManager::eval(
     const DebugFlags debug_flags = context.options()["debug"].get<DebugFlags>();
     const bool profile = debug_flags & DebugFlags::Profile;
     if (debug_flags & DebugFlags::Shell)
-        write_to_debug_buffer(format("shell:\n{}\n----\n", cmdline));
+        write_to_debug_buffer(format("shell:\n{}\n----\nargs: {}\n----\n", cmdline, join(shell_context.params | transform(shell_quote), ' ')));
 
     auto start_time = profile ? Clock::now() : Clock::time_point{};
 
     Optional<CommandFifos> command_fifos;
 
-    auto kak_env = generate_env(cmdline, context, [&](StringView name, Quoting quoting) {
+    auto kak_env = generate_env(cmdline, shell_context.params, context, [&](StringView name, Quoting quoting) {
         if (name == "command_fifo" or name == "response_fifo")
         {
             if (not command_fifos)
@@ -377,7 +382,7 @@ std::pair<String, int> ShellManager::eval(
 Shell ShellManager::spawn(StringView cmdline, const Context& context,
                           bool open_stdin, const ShellContext& shell_context)
 {
-    auto kak_env = generate_env(cmdline, context, [&](StringView name, Quoting quoting) {
+    auto kak_env = generate_env(cmdline, shell_context.params, context, [&](StringView name, Quoting quoting) {
         if (auto it = shell_context.env_vars.find(name); it != shell_context.env_vars.end())
             return it->value;
         return join(get_val(name, context) | transform(quoter(quoting)), ' ', false);