Support for command wrapping ("aliases")

Add the --wraps option to 'complete' and 'function'. This allows a
command to (recursively) inherit the completions of a wrapped command.
Fixes #393.

When evaluating a completion, we inspect the entire "wrap chain" for a
command, i.e. we follow the sequence of wrapping until we either hit a
loop (which we silently ignore) or the end of the chain. We then
evaluate completions as if the wrapping command were substituted with
the wrapped command. Currently this only works for commands, i.e.
'complete --command gco --wraps git\ checkout' won't work (that would
seem to encroaching on abbreviations anyways). It might be useful to
show an error message for that case.

The commandline builtin reflects the commandline with the wrapped
command substituted in, so e.g. git completions (which inspect the
command line) will just work. This sort of command line munging is
also performed by 'complete -C' so it's not totally without precedent.

'alias will also now mark its generated function as wrapping the
'target.

1 files changed, 53 insertions, 4 deletions

diff --git a/builtin_commandline.cpp b/builtin_commandline.cpp
index 88084c3b..0af6f656 100644
--- a/builtin_commandline.cpp
+++ b/builtin_commandline.cpp
@@ -79,6 +79,51 @@ static size_t get_cursor_pos()
     return current_cursor_pos;
 }
 
+static pthread_mutex_t transient_commandline_lock = PTHREAD_MUTEX_INITIALIZER;
+static wcstring_list_t *get_transient_stack()
+{
+    ASSERT_IS_MAIN_THREAD();
+    ASSERT_IS_LOCKED(transient_commandline_lock);
+    // A pointer is a little more efficient than an object as a static because we can elide the thread-safe initialization
+    static wcstring_list_t *result = NULL;
+    if (! result)
+    {
+        result = new wcstring_list_t();
+    }
+    return result;
+}
+
+static bool get_top_transient(wcstring *out_result)
+{
+    ASSERT_IS_MAIN_THREAD();
+    bool result = false;
+    scoped_lock locker(transient_commandline_lock);
+    const wcstring_list_t *stack = get_transient_stack();
+    if (! stack->empty())
+    {
+        out_result->assign(stack->back());
+        result = true;
+    }
+    return result;
+}
+
+builtin_commandline_scoped_transient_t::builtin_commandline_scoped_transient_t(const wcstring &cmd)
+{
+    ASSERT_IS_MAIN_THREAD();
+    scoped_lock locker(transient_commandline_lock);
+    wcstring_list_t *stack = get_transient_stack();
+    stack->push_back(cmd);
+    this->token = stack->size();
+}
+
+builtin_commandline_scoped_transient_t::~builtin_commandline_scoped_transient_t()
+{
+    ASSERT_IS_MAIN_THREAD();
+    scoped_lock locker(transient_commandline_lock);
+    wcstring_list_t *stack = get_transient_stack();
+    assert(this->token == stack->size());
+    stack->pop_back();
+}
 
 /**
    Replace/append/insert the selection with/at/after the specified string.
@@ -216,11 +261,15 @@ static int builtin_commandline(parser_t &parser, wchar_t **argv)
     int search_mode = 0;
     int paging_mode = 0;
     const wchar_t *begin = NULL, *end = NULL;
-
-    current_buffer = (wchar_t *)builtin_complete_get_temporary_buffer();
-    if (current_buffer)
+    
+    scoped_push<const wchar_t *> saved_current_buffer(&current_buffer);
+    scoped_push<size_t> saved_current_cursor_pos(&current_cursor_pos);
+    
+    wcstring transient_commandline;
+    if (get_top_transient(&transient_commandline))
     {
-        current_cursor_pos = wcslen(current_buffer);
+        current_buffer = transient_commandline.c_str();
+        current_cursor_pos = transient_commandline.size();
     }
     else
     {