feat(lsp): support version in textDocument/publishDiagnostics #36754

This commit makes it so that push diagnostics received for an outdated
document version are ignored.

test/functional/plugin/lsp/diagnostic_spec.lua

@@ -148,6 +148,40 @@ describe('vim.lsp.diagnostic', function()
       )
     end)
 
+    it('ignores outdated diagnostics', function()
+      local result = exec_lua(function()
+        vim.lsp.diagnostic.on_publish_diagnostics(nil, {
+          uri = fake_uri,
+          version = vim.lsp.util.buf_versions[diagnostic_bufnr] - 1,
+          diagnostics = {
+            _G.make_error('Error', 0, 0, 1, 0),
+          },
+        }, { client_id = client_id })
+
+        local diags = vim.diagnostic.get(diagnostic_bufnr)
+        return diags
+      end)
+
+      -- Ignored: outdated version.
+      eq(0, #result)
+
+      result = exec_lua(function()
+        vim.lsp.diagnostic.on_publish_diagnostics(nil, {
+          uri = fake_uri,
+          version = vim.lsp.util.buf_versions[diagnostic_bufnr],
+          diagnostics = {
+            _G.make_error('Error', 0, 0, 1, 0),
+          },
+        }, { client_id = client_id })
+
+        local diags = vim.diagnostic.get(diagnostic_bufnr)
+        return diags
+      end)
+
+      -- Applied: up-to-date version.
+      eq(1, #result)
+    end)
+
     it('does not create buffer on empty diagnostics', function()
       -- No buffer is created without diagnostics
       eq(