RFR: 8305457: Implement java.io.IO [v3]

[Pavel Rappo]

On Wed, 8 May 2024 10:31:59 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> If we specify that, it would be very much unlike all other `Console` methods that are covered by this:
>> 
>>     * Unless otherwise specified, passing a {@code null} argument to any method
>>     * in this class will cause a {@link NullPointerException} to be thrown.
>
> I haven't given it a try, but a brief look at the code suggests that if the console implementation backed by JLine gets used, then a `null` prompt may not generate a `NullPointerException` (since JLine appears to allow `null`) whereas if the internal JDK console implementation gets used then a `NullPointerException` will get thrown. If the expectation is to disallow a `null` prompt, then perhaps `Objects.requireNonNull(prompt)` before we hand off to the underlying console implementations might be required.

Good catch! `jdk.internal.org.jline.JdkConsoleProviderImpl.JdkConsoleImpl.readln(null)` does not throw `NullPointerException` (NPE), which it must. I'll fix the bug and add a test.

Speaking of NPE. The newly added `Console.print` and `Console.println` methods do not throw NPE if passed null. While that's how it should be, they don't specify that, so the class-level NPE clause applies:

    * Unless otherwise specified, passing a {@code null} argument to any method
    * in this class will cause a {@link NullPointerException} to be thrown.
    ...
    public sealed class Console implements Flushable permits ProxyingConsole {

I'll fix that.

We should also specify NPE (or absence thereof) on methods of `IO`. Otherwise, this package clause applies:

    * Unless otherwise noted, passing a {@code null} argument to a constructor or
    * method in any class or interface in this package will cause a
    * {@code NullPointerException} to be thrown.
    ...
    package java.io;

@stuart-marks speaking of exceptions. Do we need to add explicit `@throws` tag to `IO` methods?

    @throws {@code IOError} if {@code System.console()} returns {@code null}

While it would make sense, it would also look superfluous: we already specify that error condition in the class comment and then in every method's main description. Do we need to add one more note on `IOError`?

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PR Review Comment: https://git.openjdk.org/jdk/pull/19112#discussion_r1594013064