feat(treesitter): add vim.treesitter.show_tree() (#21322)

Add a "show_tree" function to view a textual representation of the
nodes in a language tree in a window. Moving the cursor in the
window highlights the corresponding text in the source buffer, and
moving the cursor in the source buffer highlights the corresponding
nodes in the window.

1 files changed, 184 insertions, 0 deletions

diff --git a/runtime/lua/vim/treesitter/playground.lua b/runtime/lua/vim/treesitter/playground.lua
new file mode 100644
index 0000000000..325d303df5
--- /dev/null
+++ b/runtime/lua/vim/treesitter/playground.lua
@@ -0,0 +1,184 @@
+local api = vim.api
+
+local M = {}
+
+---@class Playground
+---@field opts table Options table with the following keys:
+---                  - anon (boolean): If true, display anonymous nodes
+---                  - lang (boolean): If true, display the language alongside each node
+---
+---@class Node
+---@field id number Node id
+---@field text string Node text
+---@field named boolean True if this is a named (non-anonymous) node
+---@field depth number Depth of the node within the tree
+---@field lnum number Beginning line number of this node in the source buffer
+---@field col number Beginning column number of this node in the source buffer
+---@field end_lnum number Final line number of this node in the source buffer
+---@field end_col number Final column number of this node in the source buffer
+---@field lang string Source language of this node
+
+--- Traverse all child nodes starting at {node}.
+---
+--- This is a recursive function. The {depth} parameter indicates the current recursion level.
+--- {lang} is a string indicating the language of the tree currently being traversed. Each traversed
+--- node is added to {tree}. When recursion completes, {tree} is an array of all nodes in the order
+--- they were visited.
+---
+--- {injections} is a table mapping node ids from the primary tree to language tree injections. Each
+--- injected language has a series of trees nested within the primary language's tree, and the root
+--- node of each of these trees is contained within a node in the primary tree. The {injections}
+--- table maps nodes in the primary tree to root nodes of injected trees.
+---
+---@param node userdata Starting node to begin traversal |tsnode|
+---@param depth number Current recursion depth
+---@param lang string Language of the tree currently being traversed
+---@param injections table Mapping of node ids to root nodes of injected language trees (see
+---                        explanation above)
+---@param tree Node[] Output table containing a list of tables each representing a node in the tree
+---@private
+local function traverse(node, depth, lang, injections, tree)
+  local injection = injections[node:id()]
+  if injection then
+    traverse(injection.root, depth, injection.lang, injections, tree)
+  end
+
+  for child, field in node:iter_children() do
+    local type = child:type()
+    local lnum, col, end_lnum, end_col = child:range()
+    local named = child:named()
+    local text
+    if named then
+      if field then
+        text = string.format('%s: (%s)', field, type)
+      else
+        text = string.format('(%s)', type)
+      end
+    else
+      text = string.format('"%s"', type:gsub('\n', '\\n'))
+    end
+
+    table.insert(tree, {
+      id = child:id(),
+      text = text,
+      named = named,
+      depth = depth,
+      lnum = lnum,
+      col = col,
+      end_lnum = end_lnum,
+      end_col = end_col,
+      lang = lang,
+    })
+
+    traverse(child, depth + 1, lang, injections, tree)
+  end
+
+  return tree
+end
+
+--- Create a new Playground object.
+---
+---@param bufnr number Source buffer number
+---
+---@return Playground|nil
+---@return string|nil Error message, if any
+---
+---@private
+function M.new(self, bufnr)
+  local ok, parser = pcall(vim.treesitter.get_parser, bufnr or 0)
+  if not ok then
+    return nil, 'No parser available for the given buffer'
+  end
+
+  -- For each child tree (injected language), find the root of the tree and locate the node within
+  -- the primary tree that contains that root. Add a mapping from the node in the primary tree to
+  -- the root in the child tree to the {injections} table.
+  local root = parser:parse()[1]:root()
+  local injections = {}
+  parser:for_each_child(function(child, lang)
+    child:for_each_tree(function(tree)
+      local r = tree:root()
+      local node = root:named_descendant_for_range(r:range())
+      if node then
+        injections[node:id()] = {
+          lang = lang,
+          root = r,
+        }
+      end
+    end)
+  end)
+
+  local nodes = traverse(root, 0, parser:lang(), injections, {})
+
+  local named = {}
+  for _, v in ipairs(nodes) do
+    if v.named then
+      named[#named + 1] = v
+    end
+  end
+
+  local t = {
+    ns = api.nvim_create_namespace(''),
+    nodes = nodes,
+    named = named,
+    opts = {
+      anon = false,
+      lang = false,
+    },
+  }
+
+  setmetatable(t, self)
+  self.__index = self
+  return t
+end
+
+--- Write the contents of this Playground into {bufnr}.
+---
+---@param bufnr number Buffer number to write into.
+---@private
+function M.draw(self, bufnr)
+  vim.bo[bufnr].modifiable = true
+  local lines = {}
+  for _, item in self:iter() do
+    lines[#lines + 1] = table.concat({
+      string.rep(' ', item.depth),
+      item.text,
+      item.lnum == item.end_lnum
+          and string.format(' [%d:%d-%d]', item.lnum + 1, item.col + 1, item.end_col)
+        or string.format(
+          ' [%d:%d-%d:%d]',
+          item.lnum + 1,
+          item.col + 1,
+          item.end_lnum + 1,
+          item.end_col
+        ),
+      self.opts.lang and string.format(' %s', item.lang) or '',
+    })
+  end
+  api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+  vim.bo[bufnr].modifiable = false
+end
+
+--- Get node {i} from this Playground object.
+---
+--- The node number is dependent on whether or not anonymous nodes are displayed.
+---
+---@param i number Node number to get
+---@return Node
+---@private
+function M.get(self, i)
+  local t = self.opts.anon and self.nodes or self.named
+  return t[i]
+end
+
+--- Iterate over all of the nodes in this Playground object.
+---
+---@return function Iterator over all nodes in this Playground
+---@return table
+---@return number
+---@private
+function M.iter(self)
+  return ipairs(self.opts.anon and self.nodes or self.named)
+end
+
+return M