Fix lighttpd PATH_INFO extraction with MAPSERVER_BASE_PATH

[Copilot]

path_info.lua used Lua's gsub with a pattern built from MAPSERVER_BASE_PATH, which fails to correctly set request.path-info in lighttpd's mod_magnet environment — breaking mapfile alias resolution and ows_onlineresource construction in WMS GetCapabilities when the mapfile is specified as a path component.

Changes

• runtime/etc/lighttpd/path_info.lua: Replace gsub-based extraction with plain-text find, as suggested in the upstream report:

  -- Before (broken)
  local result = path:gsub("^" .. base_path, "")
  lighty.r.req_attr["request.path-info"] = result
  
  -- After
  local base_i = path:find(base_path, 1, true)
  local base_l = base_path:len()
  if base_i == 1 and path:len() > base_l then
      lighty.r.req_attr["request.path-info"] = path:sub(base_l + 1)
  end

  find(..., 1, true) uses plain-text matching (no pattern interpretation), correctly stripping the base path and leaving the mapfile component as PATH_INFO.

• acceptance_tests/test_wms.py: Add test_lighttpd_capabilities_url — verifies that GetMap operation URLs in the WMS GetCapabilities response start with BASE_URL_LIGHTTPD (i.e., include the correct base path + mapfile path), catching the PATH_INFO regression described in the issue.

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[sbrunner]

@johannes Does it looks good to you?

[johannes]

I wouldn't use variable names base_i and base_l (i index, l length?)

But I am not the person you were looking for :)

[johanez]

Thanks for the quick reaction @sbrunner .

Turns out I missed that mapserver uses lighty.r.req_attr["uri.path"] as SCRIPT_NAME, which together with PATH_INFO is used to dynamically construct the online-resource urls or GetCapabilties etc. if not defined in the mapfile.

So with my solution above, this duplicates the PATH_INFO part in the returned urls, e.g.: https://example.com/base_path/mapname/ogcapi/collections/mapname/ogcapi/collections/ in the output of https://example.com/base_path/mapname/ogcapi.

So one needs to remove the PATH_INFO path from lighty.r.req_attr["uri.path"]. (Which is discouraged, but seems to do no harm with mapserver).

So I end up with:

local base_path = os.getenv("MAPSERVER_BASE_PATH", "")
local path = lighty.r.req_attr["uri.path"]
local base_index = path:find(base_path, 1, true)
local base_length = base_path:len()

if base_index == 1 and path:len() > base_length  then
    lighty.r.req_attr["uri.path"] = base_path
    lighty.r.req_attr["request.path-info"] = path:sub(base_length + 1)
end