fix(api): nvim_set_keymap() throws error even in pcall() #33228

Problem: When `nvim_set_keymap` tries to overwrite a `<unique>` mapping,
it throws an error even when called in `pcall`.

Solution: src/nvim/mapping.c:buf_do_map no longer calls `semsg`. Its
callers now decide whether to ignore the error, or use
`semsg` (not caught)/`api_set_error` (caught by `pcall`).

1 files changed, 20 insertions, 0 deletions

diff --git a/test/functional/api/keymap_spec.lua b/test/functional/api/keymap_spec.lua
index acaccee4e5..2c44905274 100644
--- a/test/functional/api/keymap_spec.lua
+++ b/test/functional/api/keymap_spec.lua
@@ -1465,4 +1465,24 @@ describe('nvim_buf_set_keymap, nvim_buf_del_keymap', function()
     eq(1, exec_lua [[return GlobalCount]])
     eq('\nNo mapping found', n.exec_capture('nmap <C-I>'))
   end)
+
+  it('does not overwrite in <unique> mappings', function()
+    api.nvim_buf_set_keymap(0, 'i', 'lhs', 'rhs', {})
+    eq(
+      'E227: Mapping already exists for lhs',
+      pcall_err(api.nvim_buf_set_keymap, 0, 'i', 'lhs', 'rhs', { unique = true })
+    )
+
+    api.nvim_buf_set_keymap(0, 'ia', 'lhs2', 'rhs2', {})
+    eq(
+      'E226: Abbreviation already exists for lhs2',
+      pcall_err(api.nvim_buf_set_keymap, 0, 'ia', 'lhs2', 'rhs2', { unique = true })
+    )
+
+    api.nvim_set_keymap('n', 'lhs', 'rhs', {})
+    eq(
+      'E225: Global mapping already exists for lhs',
+      pcall_err(api.nvim_buf_set_keymap, 0, 'n', 'lhs', 'rhs', { unique = true })
+    )
+  end)
 end)