The longer explanation can be found in the comment in qurl.cpp. The
short version is as follows:
Up to now, we considered that every character could be replaced with
its percent-encoding equivalent and vice-versa, so long as the parsing
of the URL did not change. For example, x:/path+path and
x:/path%2Bpath were the same. However, to do this and yet be compliant
with most URL uses in the real world, we had to add exceptions:
- "/" and "%2F" were not the same in the path, despite the delimiter
being behind (rationale was the complex definition of path)
- "+" and "%2B" were not the same in the query, so we ended up not
transforming any sub-delim in the query at all
Now, we change our understanding based on the following line from
RFC 3986 section 2.2:
URIs that differ in the replacement of a reserved character with
its corresponding percent-encoded octet are not equivalent.
From now on, QUrl will not replace any sub-delim or gen-delim
("reserved character"), except where such a character could not exist
in the first place. This simplifies the code and removes all
exceptions.
As a side-effect, this has also changed the behaviour of the "{" and
"}" characters, which we previously allowed to remain decoded.
[ChangeLog][Important Behavior Changes][QUrl and QUrlQuery] QUrl no
longer considers all delimiter characters equivalent to their
percent-encoded forms. Now, both classes always keep all delimiters
exactly as they were in the original URL text.
[ChangeLog][Important Behavior Changes][QUrl and QUrlQuery] QUrl no
longer decodes %7B and %7D to "{" and "}" in the output of toString()
Task-number: QTBUG-31660
Change-Id: Iba0b5b31b269635ac2d0adb2bb0dfb74c139e08c
Reviewed-by: David Faure (KDE) <faure@kde.org>
993bbb4d4b