Keep encode_python_string() in front/php/server/util.php, replacing
encode_single_quotes() in place, and remove the standalone
app_conf_encode.php helper file and its require.
Rework the regression test to dispatch the real util.php savesettings
path through the PHP CLI against temporary synthetic config, API and
session directories, covering both scalar string and array string
settings: the generated app.conf must compile with warnings as errors
and parse back to the typed values.
The existing {s-quote} lifecycle is preserved (single quotes are still
written as {s-quote} and converted back by the same consumers), and the
app.conf readers in initialise.py and plugin_helper.py are unchanged.
app.conf is written by util.php saveSettings() as Python source and later
compiled/exec'd by the backend. String settings were emitted into
single-quoted Python literals with only ' encoded (as {s-quote}), so
backslashes were written raw. A regex such as 192\.0\.2\..* then produced
"SyntaxWarning: invalid escape sequence '\.'", valid Python escapes such as
\n were silently reinterpreted, and a trailing backslash made the file fail
to compile.
Move the encoder into a side-effect-free helper, app_conf_encode.php, as
encode_python_string(). It now doubles backslashes before the existing
{s-quote} replacement, so backslashes round-trip unchanged through app.conf
serialization and Python parsing, while single quotes keep using the legacy
{s-quote} placeholder. Both scalar string and array string serialization use
the helper.
Add regression tests that run the real PHP helper through the PHP CLI,
compile the generated source with warnings promoted to errors, and check
the scalar and array round trips.
Panagiotis Koilakos