[lprnmns]

WsgiToAsgiInstance.build_environ() strips root_path from the start of path with a plain startswith, so it also strips it when root_path is only a prefix of the first path segment:

scope = {"root_path": "/app", "path": "/application/foo", ...}
# SCRIPT_NAME = "/app", PATH_INFO = "lication/foo"

PATH_INFO then doesn't even start with /.

This only strips root_path when the path is exactly root_path or continues with / after it, which is the same rule Starlette uses in get_route_path. Otherwise PATH_INFO is left as the full path, the same as it already is for paths that don't start with root_path at all.

Tests: a parametrized test_script_name_segment_boundary covering an exact match, a trailing slash, a non-matching segment prefix (/base vs /basement/foo) and an empty root_path. The /basement case fails on main. The full test suite, black, isort and flake8 pass.