Dont create empty diagnostic messages

[mediremi]

VS Code throws a TypeError: message not sent error if a diagnostic message is blank:

https://github.com/microsoft/vscode/blob/3aef8be5e46aa7e97e8b0ed115f6147cd0b24634/src/vs/workbench/api/common/extHostTypes.ts#L1183-L1185

We create diagnostics with empty messages if diagnosticMessage is an empty array, which happens if parsedDiagnostic.content is empty or has only 1 element:

rescript-vscode/server/src/utils.ts

Lines 699 to 707 in ef518a9

	let [fileAndRangeLine, ...diagnosticMessage] = parsedDiagnostic.content;
	let { file, range } = parseFileAndRange(fileAndRangeLine);
	if (result[file] == null) {
	result[file] = [];
	}
	// remove start and end whitespaces/newlines
	let message = diagnosticMessage.join("\n").trim()

The compiler log message FAILED: cannot make progress due to previous errors. is converted to a diagnostic message with content: [line], which triggers this condition:

rescript-vscode/server/src/utils.ts

Lines 571 to 578 in 5b76419

	} else if (line.startsWith("FAILED:")) {
	// File with a self cycle
	parsedDiagnostics.push({
	code: undefined,
	severity: t.DiagnosticSeverity.Error,
	tag: undefined,
	content: [line],
	});

In addition to adding a check for message != "" before creating a diagnostic message, I've also changed the compiler log output parser to skip the following errors messages:

• FAILED: cannot make progress due to previous errors
• FAILED: dependency cycle

These errors don't currently contain filepath/range information and so we cannot create diagnostic messages for them anyway (though with some tweaking on the compiler side, we might be able to output filepaths for dependency cycle errors.)

[zth]

Side note - outputting dependency issues in the compiler would be a massive (and necessary) improvement.