RFD: Use of ~ (tilde) when considering local and non-local file URLs

[Jaikiran Pai]

Hello Eirik,

The code in URLJarFile which does that check for "~" seems to have been 
introduced for https://bugs.openjdk.org/browse/JDK-4447921. It doesn't 
tell why the "~" was necessary.

In any case, I don't think any kind of clean up or introducing tests for 
"~" is worth it, given it's not clear what that usage signifies.

-Jaikiran

On 26/03/25 3:43 pm, Eirik Bjørsnøs wrote:
> Hi,
>
> Various URL scheme code paths contain branches for local or non-local 
> file URLs:
>
> See URLJarFile::isFileURL for an example where the host is compared as 
> follows:
>
>     String host = url.getHost();
>     if (host == null || host.isEmpty() || host.equals("~") ||
>     host.equalsIgnoreCase("localhost"))
>         return true;
>
>
> Equivalent checks are found in unix and windows Handler::openConnection.
>
> In JarFileFactory::urlFor however, the logic is slightly different in 
> that the comparison with ~ (tilde) is missing:
>
>     String host = url.getHost();
>     if (host != null && !host.isEmpty() &&
>     !host.equalsIgnoreCase("localhost")) {
>
> I have tried to find an RFC or any other mention of "~" in host names, 
> but found nothing. Can anyone shine light on the meaning and 
> interpretation of this character as a host name?
>
> In any case, I think if we could add the tilde logic 
> to JarFileFactory::urlFor, then all these four checks would be 
> equivalent and a prime candidate for a consolidating cleanup PR, 
> perhaps also expanding a bit on the documentation for the consolidated 
> method(s).
>
> My take is that the missing test was a simple oversight, that adding 
> it should not be harmful and that this would enable a nice 
> consolidation of this particular logic. .
>
> Thoughts?
>
> Eirik.
>
>
>
>
>
>
>
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