nvim (diagnostic): add treesitter diagnostics

nvim/dot-config/nvim/plugin/treesitter_diagnostic.lua

@@ -0,0 +1,89 @@
+--- language-independent query for syntax errors and missing elements
+local error_query = vim.treesitter.query.parse("query", "[(ERROR)(MISSING)] @a")
+local namespace = vim.api.nvim_create_namespace("treesitter.diagnostics")
+
+--- @param args vim.api.keyset.create_autocmd.callback_args
+local function diagnose(args)
+  if not vim.diagnostic.is_enabled({ bufnr = args.buf }) then
+    return
+  end
+  -- don't diagnose strange stuff
+  if vim.bo[args.buf].buftype ~= "" then
+    return
+  end
+
+  local diagnostics = {}
+  local parser = vim.treesitter.get_parser(args.buf, nil, { error = false })
+  if parser then
+    parser:parse(false, function(_, trees)
+      if not trees then
+        return
+      end
+      parser:for_each_tree(function(tree, ltree)
+        -- only process trees containing errors
+        if tree:root():has_error() then
+          for _, node in error_query:iter_captures(tree:root(), args.buf) do
+            local function process_node()
+              local lnum, col, end_lnum, end_col = node:range()
+
+              -- collapse nested syntax errors that occur at the exact same position
+              local parent = node:parent()
+              if parent and parent:type() == "ERROR" and parent:range() == node:range() then
+                return
+              end
+
+              -- clamp large syntax error ranges to just the line to reduce noise
+              if end_lnum > lnum then
+                end_lnum = lnum + 1
+                end_col = 0
+              end
+
+              --- @type vim.Diagnostic
+              local diagnostic = {
+                source = "treesitter",
+                lnum = lnum,
+                end_lnum = end_lnum,
+                col = col,
+                end_col = end_col,
+                message = "",
+                code = string.format("%s-syntax", ltree:lang()),
+                bufnr = args.buf,
+                namespace = namespace,
+                severity = vim.diagnostic.severity.ERROR,
+              }
+              if node:missing() then
+                diagnostic.message = string.format("missing `%s`", node:type())
+              else
+                diagnostic.message = "error"
+              end
+
+              -- add context to the error using sibling and parent nodes
+              local previous = node:prev_sibling()
+              if previous and previous:type() ~= "ERROR" then
+                local previous_type = previous:named() and previous:type() or string.format("`%s`", previous:type())
+                diagnostic.message = diagnostic.message .. " after " .. previous_type
+              end
+
+              if parent and parent:type() ~= "ERROR" and (previous == nil or previous:type() ~= parent:type()) then
+                diagnostic.message = diagnostic.message .. " in " .. parent:type()
+              end
+
+              table.insert(diagnostics, diagnostic)
+            end
+
+            process_node()
+          end
+        end
+      end)
+    end)
+    vim.diagnostic.set(namespace, args.buf, diagnostics)
+  end
+end
+
+local autocmd_group = vim.api.nvim_create_augroup("editor.treesitter", { clear = true })
+
+vim.api.nvim_create_autocmd({ "FileType", "TextChanged", "InsertLeave" }, {
+  desc = "treesitter diagnostics",
+  group = autocmd_group,
+  callback = vim.schedule_wrap(diagnose),
+})