feat: formatters can use $RELATIVE_FILEPATH in args (#349)

1 files changed, 68 insertions, 0 deletions

diff --git a/lua/conform/fs.lua b/lua/conform/fs.lua
index d303dbd..6f92e18 100644
--- a/lua/conform/fs.lua
+++ b/lua/conform/fs.lua
@@ -15,4 +15,72 @@ M.join = function(...)
   return table.concat({ ... }, M.sep)
 end
 
+M.is_absolute = function(path)
+  if M.is_windows then
+    return path:lower():match("^%a:")
+  else
+    return vim.startswith(path, "/")
+  end
+end
+
+M.abspath = function(path)
+  if not M.is_absolute(path) then
+    path = vim.fn.fnamemodify(path, ":p")
+  end
+  return path
+end
+
+--- Returns true if candidate is a subpath of root, or if they are the same path.
+---@param root string
+---@param candidate string
+---@return boolean
+M.is_subpath = function(root, candidate)
+  if candidate == "" then
+    return false
+  end
+  root = vim.fs.normalize(M.abspath(root))
+  -- Trim trailing "/" from the root
+  if root:find("/", -1) then
+    root = root:sub(1, -2)
+  end
+  candidate = vim.fs.normalize(M.abspath(candidate))
+  if M.is_windows then
+    root = root:lower()
+    candidate = candidate:lower()
+  end
+  if root == candidate then
+    return true
+  end
+  local prefix = candidate:sub(1, root:len())
+  if prefix ~= root then
+    return false
+  end
+
+  local candidate_starts_with_sep = candidate:find("/", root:len() + 1, true) == root:len() + 1
+  local root_ends_with_sep = root:find("/", root:len(), true) == root:len()
+
+  return candidate_starts_with_sep or root_ends_with_sep
+end
+
+---Create a relative path from the source to the target
+---@param source string
+---@param target string
+---@return string
+M.relative_path = function(source, target)
+  source = M.abspath(source)
+  target = M.abspath(target)
+  local path = {}
+  while not M.is_subpath(source, target) do
+    table.insert(path, "..")
+    local new_source = vim.fs.dirname(source)
+    assert(source ~= new_source)
+    source = new_source
+  end
+
+  local offset = vim.endswith(source, M.sep) and 1 or 2
+  local rel_target = target:sub(source:len() + offset)
+  table.insert(path, rel_target)
+  return M.join(unpack(path))
+end
+
 return M