Escape multiline strings containing triple quotes in to_hocon

[gaoflow]

Summary

HOCONConverter.to_hocon emits any string containing a newline as a triple-quoted ("""...""") literal — even when the string itself contains a """ sequence. The embedded """ terminates the literal early, so the output either fails to re-parse or silently drops the """ markers, breaking the to_hocon → parse round-trip.

from pyhocon import ConfigFactory
from pyhocon.converter import HOCONConverter

out = HOCONConverter.to_hocon(ConfigFactory.from_dict({"k": 'a\nb"""c'}))
# -> k = """a\nb"""c"""
ConfigFactory.parse_string(out)   # ParseException

out = HOCONConverter.to_hocon(ConfigFactory.from_dict({"k": 'before\n"""middle"""\nafter'}))
ConfigFactory.parse_string(out)["k"]   # silently 'before\nmiddle\nafter' — the """ markers dropped

to_json handles the identical values correctly, confirming the value is representable.

Cause

In to_hocon (pyhocon/converter.py), both the str branch and the ConfigQuotedString branch chose the """...""" form solely on the presence of a newline:

if '\n' in config and len(config) > 1:
    lines = '"""{value}"""'.format(value=config)  # multilines

This ignores that a HOCON triple-quoted string cannot contain the """ sequence.

Fix

Only use the triple-quoted form when the value does not contain """; otherwise fall through to the existing escaped single-quoted path (_escape_string, which already escapes \n → \n). Applied to both branches. Normal multiline strings (no """) are unchanged, preserving test_format_multiline_string.

Verification

• Added test_format_multiline_string_with_triple_quote, which asserts the escaped output form and round-trips three """-containing values through the parser. It fails before the fix and passes after.
• Full suite: 309 passed, 1 xfailed (was 308 + 1 xfailed; no regressions). flake8 pyhocon tests setup.py exits 0.

This pull request was prepared with the assistance of AI, under my direction and review.