API: nvim_set_keymap, nvim_del_keymap #9924

closes #9136

- Treat empty {rhs} like <Nop>

- getchar.c: Pull "repl. MapArg termcodes" into func
  The "preprocessing code" surrounding the replace_termcodes calls needs
  to invoke replace_termcodes, and also check if RHS is equal to "<Nop>".
  To reduce code duplication, factor this out into a helper function.

  Also add an rhs_is_noop flag to MapArguments; buf_do_map_explicit
  expects an empty {rhs} string for "<Nop>", but also needs to distinguish
  that from something like ":map lhs<cr>" where no {rhs} was provided.

- getchar.c: Use allocated buffer for rhs in MapArgs
  Since the MAXMAPLEN limit does not apply to the RHS of a mapping (or
  else an RHS that calls a really long autoload function from a plugin
  would be incorrectly rejected as being too long), use an allocated
  buffer for RHS rather than a static buffer of length MAXMAPLEN + 1.

- Mappings LHS and RHS can contain literal space characters, newlines, etc.

- getchar.c: replace_termcodes in str_to_mapargs
  It makes sense to do this; str_to_mapargs is, intuitively, supposed to
  take a "raw" command string and parse it into a totally "do_map-ready"
  struct.

- api/vim.c: Update lhs, rhs len after replace_termcodes
  Fixes a bug in which replace_termcodes changes the length of lhs or rhs,
  but the later search through the mappings/abbreviations hashtables
  still uses the old length value. This would cause the search to fail
  erroneously and throw 'E31: No such mapping' errors or 'E24: No such
  abbreviation' errors.

- getchar: Create new map_arguments struct
  So that a string of map arguments can be parsed into a more useful, more
  portable data structure.

- getchar.c: Add buf_do_map function
  Exactly the same as the old do_map, but replace the hardcoded references
  to the global `buf_T* curbuf` with a function parameter so that we can
  invoke it from nvim_buf_set_keymap.

- Remove gettext calls in do_map error handling

src/nvim/api/buffer.c

@@ -15,6 +15,7 @@
 #include "nvim/buffer.h"
 #include "nvim/charset.h"
 #include "nvim/cursor.h"
+#include "nvim/getchar.h"
 #include "nvim/memline.h"
 #include "nvim/memory.h"
 #include "nvim/misc1.h"
@@ -576,6 +577,27 @@ ArrayOf(Dictionary) nvim_buf_get_keymap(Buffer buffer, String mode, Error *err)
   return keymap_array(mode, buf);
 }
 
+/// Like |nvim_set_keymap|, but for a specific buffer.
+///
+/// @param  buffer  Buffer handle, or 0 for the current buffer.
+void nvim_buf_set_keymap(Buffer buffer, String mode, String lhs, String rhs,
+                         Dictionary opts, Error *err)
+  FUNC_API_SINCE(6)
+{
+  modify_keymap(buffer, false, mode, lhs, rhs, opts, err);
+}
+
+/// Like |nvim_del_keymap|, but for a specific buffer.
+///
+/// @param  buffer  Buffer handle, or 0 for the current buffer.
+void nvim_buf_del_keymap(Buffer buffer, String mode, String lhs, Error *err)
+  FUNC_API_SINCE(6)
+{
+  String rhs = { .data = "", .size = 0 };
+  Dictionary opts = ARRAY_DICT_INIT;
+  modify_keymap(buffer, true, mode, lhs, rhs, opts, err);
+}
+
 /// Gets a map of buffer-local |user-commands|.
 ///
 /// @param  buffer  Buffer handle, or 0 for current buffer