feat(diagnostic): enable(…, opts)

Problem:
vim.diagnostic.enable() does not match the signature of vim.lsp.inlay_hint.enable()

Solution:
- Change the signature so that the first 2 args are (bufnr, enable).
- Introduce a 3rd `opts` arg.
    - Currently it only supports `opts.ns_id`.

4 files changed, 66 insertions, 26 deletions

diff --git a/runtime/doc/develop.txt b/runtime/doc/develop.txt
index a7373c84b3..6c27e4775f 100644
--- a/runtime/doc/develop.txt
+++ b/runtime/doc/develop.txt
@@ -372,11 +372,13 @@ Use existing common {verb} names (actions) if possible:
     - create:       Creates a new (non-trivial) thing (TODO: rename to "def"?)
     - del:          Deletes a thing (or group of things)
     - detach:       Dispose attached listener (TODO: rename to "un"?)
+    - enable:       Enables/disables functionality.
     - eval:         Evaluates an expression
     - exec:         Executes code
     - fmt:          Formats
     - get:          Gets things (often by a query)
     - inspect:      Presents a high-level, often interactive, view
+    - is_enabled:   Checks if functionality is enabled.
     - open:         Opens something (a buffer, window, …)
     - parse:        Parses something into a structured form
     - set:          Sets a thing (or group of things)
diff --git a/runtime/doc/diagnostic.txt b/runtime/doc/diagnostic.txt
index 1f3f1c80fe..1826cc4c08 100644
--- a/runtime/doc/diagnostic.txt
+++ b/runtime/doc/diagnostic.txt
@@ -367,6 +367,13 @@ Lua module: vim.diagnostic                                    *diagnostic-api*
       • {user_data}?  (`any`) arbitrary data plugins can add
       • {namespace}?  (`integer`)
 
+*vim.diagnostic.Filter*
+    Extends: |vim.diagnostic.Opts|
+
+
+    Fields: ~
+      • {ns_id}?  (`integer`) Namespace
+
 *vim.diagnostic.GetOpts*
     A table with the following keys:
 
@@ -616,7 +623,7 @@ count({bufnr}, {opts})                                *vim.diagnostic.count()*
         (`table`) Table with actually present severity values as keys (see
         |diagnostic-severity|) and integer counts as values.
 
-enable({bufnr}, {namespace}, {enable})               *vim.diagnostic.enable()*
+enable({bufnr}, {enable}, {opts})                    *vim.diagnostic.enable()*
     Enables or disables diagnostics.
 
     To "toggle", pass the inverse of `is_enabled()`: >lua
@@ -624,11 +631,12 @@ enable({bufnr}, {namespace}, {enable})               *vim.diagnostic.enable()*
 <
 
     Parameters: ~
-      • {bufnr}      (`integer?`) Buffer number, or 0 for current buffer, or
-                     `nil` for all buffers.
-      • {namespace}  (`integer?`) Only for the given namespace, or `nil` for
-                     all.
-      • {enable}     (`boolean?`) true/nil to enable, false to disable
+      • {bufnr}   (`integer?`) Buffer number, or 0 for current buffer, or
+                  `nil` for all buffers.
+      • {enable}  (`boolean?`) true/nil to enable, false to disable
+      • {opts}    (`vim.diagnostic.Filter?`) Filter by these opts, or `nil`
+                  for all. Only `ns_id` is supported, currently. See
+                  |vim.diagnostic.Filter|.
 
 fromqflist({list})                               *vim.diagnostic.fromqflist()*
     Convert a list of quickfix items to a list of diagnostics.
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 8609d84506..d320db4e51 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -421,7 +421,8 @@ The following changes to existing APIs or features add new behavior.
 • |vim.diagnostic.get()| and |vim.diagnostic.count()| accept multiple
   namespaces rather than just a single namespace.
 
-• |vim.diagnostic.enable()| accepts an `enabled` boolean parameter.
+• |vim.diagnostic.enable()| gained new parameters, and the old signature is
+  deprecated.
 
 • Extmarks now fully support multi-line ranges, and a single extmark can be
   used to highlight a range of arbitrary length. The |nvim_buf_set_extmark()|
diff --git a/runtime/lua/vim/diagnostic.lua b/runtime/lua/vim/diagnostic.lua
index 26374aa055..4fcbfa7507 100644
--- a/runtime/lua/vim/diagnostic.lua
+++ b/runtime/lua/vim/diagnostic.lua
@@ -239,6 +239,9 @@ local M = {}
 --- whole line the sign is placed in.
 --- @field linehl? table<vim.diagnostic.Severity,string>
 
+--- @class vim.diagnostic.Filter : vim.diagnostic.Opts
+--- @field ns_id? integer Namespace
+
 --- @nodoc
 --- @enum vim.diagnostic.Severity
 M.severity = {
@@ -1538,13 +1541,7 @@ end
 
 --- @deprecated use `vim.diagnostic.is_enabled()`
 function M.is_disabled(bufnr, namespace)
-  vim.deprecate(
-    'Defining diagnostic signs with :sign-define or sign_define()',
-    'vim.diagnostic.is_enabled()',
-    '0.12',
-    nil,
-    false
-  )
+  vim.deprecate('vim.diagnostic.is_disabled()', 'vim.diagnostic.is_enabled()', '0.12', nil, false)
   return not M.is_enabled(bufnr, namespace)
 end
 
@@ -1591,7 +1588,7 @@ function M.show(namespace, bufnr, diagnostics, opts)
     return
   end
 
-  if M.is_disabled(bufnr, namespace) then
+  if not M.is_enabled(bufnr, namespace) then
     return
   end
 
@@ -1942,7 +1939,7 @@ function M.disable(bufnr, namespace)
     nil,
     false
   )
-  M.enable(bufnr, namespace, false)
+  M.enable(bufnr, false, { ns_id = namespace })
 end
 
 --- Enables or disables diagnostics.
@@ -1954,17 +1951,49 @@ end
 --- ```
 ---
 --- @param bufnr integer? Buffer number, or 0 for current buffer, or `nil` for all buffers.
---- @param namespace integer? Only for the given namespace, or `nil` for all.
 --- @param enable (boolean|nil) true/nil to enable, false to disable
-function M.enable(bufnr, namespace, enable)
+--- @param opts vim.diagnostic.Filter? Filter by these opts, or `nil` for all. Only `ns_id` is
+--- supported, currently.
+function M.enable(bufnr, enable, opts)
+  opts = opts or {}
+  if type(enable) == 'number' then
+    -- Legacy signature.
+    vim.deprecate(
+      'vim.diagnostic.enable(buf:number, namespace)',
+      'vim.diagnostic.enable(buf:number, enable:boolean, opts)',
+      '0.12',
+      nil,
+      false
+    )
+    opts.ns_id = enable
+    enable = true
+  end
   vim.validate({
     bufnr = { bufnr, 'n', true },
-    namespace = { namespace, 'n', true },
-    enable = { enable, 'b', true },
+    enable = {
+      enable,
+      function(o)
+        return o == nil or type(o) == 'boolean' or type(o) == 'number'
+      end,
+      'boolean or number (deprecated)',
+    },
+    opts = {
+      opts,
+      function(o)
+        return o == nil
+          or (
+            type(o) == 'table'
+            -- TODO(justinmk): support other `vim.diagnostic.Filter` fields.
+            and (vim.tbl_isempty(o) or vim.deep_equal(vim.tbl_keys(o), { 'ns_id' }))
+          )
+      end,
+      'vim.diagnostic.Filter table (only ns_id is supported currently)',
+    },
   })
   enable = enable == nil and true or enable
+
   if bufnr == nil then
-    if namespace == nil then
+    if opts.ns_id == nil then
       diagnostic_disabled = (
         enable
           -- Enable everything by setting diagnostic_disabled to an empty table.
@@ -1978,12 +2007,12 @@ function M.enable(bufnr, namespace, enable)
         })
       )
     else
-      local ns = M.get_namespace(namespace)
+      local ns = M.get_namespace(opts.ns_id)
       ns.disabled = not enable
     end
   else
     bufnr = get_bufnr(bufnr)
-    if namespace == nil then
+    if opts.ns_id == nil then
       diagnostic_disabled[bufnr] = (not enable) and true or nil
     else
       if type(diagnostic_disabled[bufnr]) ~= 'table' then
@@ -1993,14 +2022,14 @@ function M.enable(bufnr, namespace, enable)
           diagnostic_disabled[bufnr] = {}
         end
       end
-      diagnostic_disabled[bufnr][namespace] = (not enable) and true or nil
+      diagnostic_disabled[bufnr][opts.ns_id] = (not enable) and true or nil
     end
   end
 
   if enable then
-    M.show(namespace, bufnr)
+    M.show(opts.ns_id, bufnr)
   else
-    M.hide(namespace, bufnr)
+    M.hide(opts.ns_id, bufnr)
   end
 end