dumps() does not quote values containing '=', producing output the parser misreads

[anthonyoteri]

Bug

dumps() does not quote string values that contain =. The resulting output is structurally ambiguous: the parser's lexer treats = as the assignment operator EQ, so a value like foo=bar is tokenized as three separate tokens (foo, EQ, bar) rather than a single value.

The round-trip loads(dumps(data)) == data fails for any value containing =.

Reproducer

import structprop
out = structprop.dumps({"k": "foo=bar"})
print(repr(out))   # 'k = foo=bar\n'
back = structprop.loads(out)
# ParserError or silently wrong result — 'bar' is parsed as a stray token

Root cause

_ESCAPE_CHARACTERS is defined as ' \t' — only space and tab. The = character is a special token in the lexer but is absent from the escape set.

Fix

Extend _ESCAPE_CHARACTERS (or the escape logic) to include all characters that the lexer treats as special: =, {, }, #, newline, and carriage return:

_ESCAPE_CHARACTERS = ' \t\n\r#{}='