Long diagnostic message field

[ratmice]

In the bug I filed yesterday #1458 discusses tranfsering documents from server to client.
The impetus for that request though was dealing with long diagnostic messages.

Thinking through it a different solution than #1458 might be instead adding an long_message?: string field to diagnostic. This would appear to be a much simpler fix for the problem that I am dealing with, having less weirdness involving uri for the lsp server, and new request types.

[RobbyCBennett]

For a long description, the LSP should support both dynamic and static descriptions. Here's an idea of how this could be implemented.

In CodeDescription add dynamicDescription as an optional string. Make href optional.

export interface CodeDescription {
	/**
	 * An URI to open with general information about the diagnostic error (e.g.
	 * paragraphs of a description, code examples, exceptions, links to sources).
	 * The URI can start with "file:", "https:", or other.
	 */
	href?: URI;

	/**
	 * A string with unique information about this particular instance of the
	 * diagnostic error (e.g. a warning that mentions your variable name
	 * specifcally and the function it was defined in).
	 */
	dynamicDescription?: string;
}

Add a textDocument/publishDiagnosticLongDescriptions method, as a notification from the server to the client. This is to avoid repetition of the long descriptions.

interface PublishDiagnosticLongDescriptionParams extends WorkDoneProgressParams {
	/**
	 * An array of long descriptions for each diagnostic
	 */
	diagnosticLongDescriptions: DiagnosticLongDescription[];
}

interface DiagnosticLongDescription {
	/**
	 * The diagnostic's code, which might appear in the user interface.
	 */
	code: integer | string;

	/**
	 * The static long description of a diagnostic (e.g. paragraphs of a
	 * description, code examples, exceptions, links to sources).
	 */
	longDescription: string;
}

[RobbyCBennett]

This is a highly requested feature with VS Code, specifically for long dynamic diagnostic descriptions.