If the user specifies an unusable Java, let them know that the binary will be used

[datho7561]

Provides a popup that explains what happened and has buttons to:

• Set "prefer binary" to true so they don't see the popup again
• Provide the download link for Java so they can update Java if necessary

This popup only appears when the user has configured "xml.java.home" or "java.home" (either to an outdated or non-existant JDK/JRE) and this popup doesn't block the language server startup (i.e. we go ahead and launch the binary server before the user clicks anything on the popup).

[rgrunber]

I haven't reviewed this thoroughly, but noticed the workflow seems to be :

Check if some JRE on the system is compatible -> If not, try the binary server

However, if the binary server fails (eg. not trusted, and we don't trust it), we seem to be trying Java once again :

vscode-xml/src/server/serverStarter.ts

Lines 53 to 62 in 53f04ba

	const javaServerMessage = hasJava ? 'Falling back to the Java server.' : 'Cannot start XML language server, since Java is missing.';
	if (e === ABORTED_ERROR) {
	window.showWarningMessage(`${e.message}. ${javaServerMessage}`);
	} else {
	window.showErrorMessage(`${e}. ${javaServerMessage}`);
	}
	if (!hasJava) {
	throw new Error("Failed to launch binary XML language server and no Java is installed");
	}
	return prepareJavaExecutable(context, requirements, xmlJavaExtensions);

I would just make sure that works as expected.

[datho7561]

I get an error popup that says:

Activating extension 'redhat.vscode-xml' failed: Failed to launch binary XML language server and no Java is installed.

[rgrunber]

Seems fine to me. The only odd thing I found was :

I simulated Java 8 being detected, and got one warning prompt regarding the version being insufficient, and the option to download java / always use binary server. The other prompt is from the natural flow of the program to attempt to use the binary server. Probably won't happen normally, since I am using a locally built/untrusted binary.

I guess there's nothing too wrong here because the first prompt is more informational, and the user need not make a decision there.