feat(lsp): implement vim.lsp.diagnostic.redraw() (#15203)

Add a new function to redraw diagnostics from the current diagnostic
cache, without receiving a "publishDiagnostics" message from the server.
This is already being done in two places in the Lua stdlib, so this
function unifies that functionality in addition to providing it to third
party plugins.

An example use case for this could be a command or key-binding for
toggling diagnostics virtual text. The virtual text configuration option
can be toggled using `vim.lsp.with` followed by
`vim.lsp.diagnostic.redraw()` to immediately redraw the diagnostics
with the updated setting.

3 files changed, 52 insertions, 21 deletions

diff --git a/runtime/doc/lsp.txt b/runtime/doc/lsp.txt
index c750a65c10..7daab4d6f1 100644
--- a/runtime/doc/lsp.txt
+++ b/runtime/doc/lsp.txt
@@ -1487,6 +1487,22 @@ on_publish_diagnostics({_}, {_}, {params}, {client_id}, {_}, {config})
                                 • Sort diagnostics (and thus signs and virtual
                                   text)
 
+redraw({bufnr}, {client_id})                     *vim.lsp.diagnostic.redraw()*
+                Redraw diagnostics for the given buffer and client
+
+                This calls the "textDocument/publishDiagnostics" handler
+                manually using the cached diagnostics already received from
+                the server. This can be useful for redrawing diagnostics after
+                making changes in diagnostics configuration.
+                |lsp-handler-configuration|
+
+                Parameters: ~
+                    {bufnr}      (optional, number): Buffer handle, defaults
+                                 to current
+                    {client_id}  (optional, number): Redraw diagnostics for
+                                 the given client. The default is to redraw
+                                 diagnostics for all attached clients.
+
 reset({client_id}, {buffer_client_map})           *vim.lsp.diagnostic.reset()*
                 Clear diagnotics and diagnostic cache
 
diff --git a/runtime/lua/vim/lsp.lua b/runtime/lua/vim/lsp.lua
index f5aefc8260..87ecc3eeea 100644
--- a/runtime/lua/vim/lsp.lua
+++ b/runtime/lua/vim/lsp.lua
@@ -453,15 +453,7 @@ local function text_document_did_open_handler(bufnr, client)
 
   -- Next chance we get, we should re-do the diagnostics
   vim.schedule(function()
-    vim.lsp.handlers["textDocument/publishDiagnostics"](
-      nil,
-      "textDocument/publishDiagnostics",
-      {
-        diagnostics = vim.lsp.diagnostic.get(bufnr, client.id),
-        uri = vim.uri_from_bufnr(bufnr),
-      },
-      client.id
-    )
+    vim.lsp.diagnostic.redraw(bufnr, client.id)
   end)
 end
 
diff --git a/runtime/lua/vim/lsp/diagnostic.lua b/runtime/lua/vim/lsp/diagnostic.lua
index 246665602d..120320becc 100644
--- a/runtime/lua/vim/lsp/diagnostic.lua
+++ b/runtime/lua/vim/lsp/diagnostic.lua
@@ -1168,6 +1168,40 @@ function M.display(diagnostics, bufnr, client_id, config)
   save_extmarks(bufnr, client_id)
 end
 
+--- Redraw diagnostics for the given buffer and client
+---
+--- This calls the "textDocument/publishDiagnostics" handler manually using
+--- the cached diagnostics already received from the server. This can be useful
+--- for redrawing diagnostics after making changes in diagnostics
+--- configuration. |lsp-handler-configuration|
+---
+--- @param bufnr (optional, number): Buffer handle, defaults to current
+--- @param client_id (optional, number): Redraw diagnostics for the given
+---        client. The default is to redraw diagnostics for all attached
+---        clients.
+function M.redraw(bufnr, client_id)
+  bufnr = get_bufnr(bufnr)
+  if not client_id then
+    return vim.lsp.for_each_buffer_client(bufnr, function(client)
+      M.redraw(bufnr, client.id)
+    end)
+  end
+
+  -- We need to invoke the publishDiagnostics handler directly instead of just
+  -- calling M.display so that we can preserve any custom configuration options
+  -- the user may have set with vim.lsp.with.
+  vim.lsp.handlers["textDocument/publishDiagnostics"](
+    nil,
+    "textDocument/publishDiagnostics",
+    {
+      uri = vim.uri_from_bufnr(bufnr),
+      diagnostics = M.get(bufnr, client_id),
+    },
+    client_id,
+    bufnr
+  )
+end
+
 -- }}}
 -- Diagnostic User Functions {{{
 
@@ -1361,18 +1395,7 @@ function M.enable(bufnr, client_id)
 
   diagnostic_disabled[bufnr][client_id] = nil
 
-  -- We need to invoke the publishDiagnostics handler directly instead of just
-  -- calling M.display so that we can preserve any custom configuration options
-  -- the user may have set with vim.lsp.with.
-  vim.lsp.handlers["textDocument/publishDiagnostics"](
-    nil,
-    "textDocument/publishDiagnostics",
-    {
-      diagnostics = M.get(bufnr, client_id),
-      uri = vim.uri_from_bufnr(bufnr),
-    },
-    client_id
-  )
+  M.redraw(bufnr, client_id)
 end
 -- }}}