Add full support for Diagnostic.code

[EstFoisy]

What it does

Closes #11659.
Add full support for Diagnostic.code according to the VS Code API.

How to test

CI should pass

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[colin-grant-work]

It looks like there's loss of information here. Is there a reason we don't want to include the target field in the code when we convert it? I notice that the corresponding code in VSCode does preserve the target:

https://github.com/microsoft/vscode/blob/65a9097aa2da4d55318073ca23bc678a2885c461/src/vs/workbench/api/common/extHostTypeConverters.ts#L198-L207

Though when they're reconstructing a Diagonstic from the DTO, they ignore the target. Not very clear (to me) why.

https://github.com/microsoft/vscode/blob/65a9097aa2da4d55318073ca23bc678a2885c461/src/vs/workbench/api/common/extHostTypeConverters.ts#L223

[vince-fugnitto]

@colin-grant-work I believe it was done this way due to the conversion of vst.Diagnostic (vscode-languageserver-types) which did not support the new type:

theia/packages/plugin-ext/src/main/browser/languages-main.ts

Lines 1072 to 1080 in e96bb5b

	function reviveMarker(marker: MarkerData): vst.Diagnostic {
	const monacoMarker: vst.Diagnostic = {
	code: marker.code,
	severity: reviveSeverity(marker.severity),
	range: reviveRange(marker.startLineNumber, marker.startColumn, marker.endLineNumber, marker.endColumn),
	message: marker.message,
	source: marker.source,
	relatedInformation: undefined
	};

/**
 * Represents a diagnostic, such as a compiler error or warning. Diagnostic objects
 * are only valid in the scope of a resource.
 */
export interface Diagnostic {
    /**
     * The range at which the message applies
     */
    range: Range;
    /**
     * The diagnostic's severity. Can be omitted. If omitted it is up to the
     * client to interpret diagnostics as error, warning, info or hint.
     */
    severity?: DiagnosticSeverity;
    /**
     * The diagnostic's code, which usually appear in the user interface.
     */
    code?: number | string;
    /**
     * A human-readable string describing the source of this
     * diagnostic, e.g. 'typescript' or 'super lint'. It usually
     * appears in the user interface.
     */
    source?: string;
    /**
     * The diagnostic's message. It usually appears in the user interface
     */
    message: string;
    /**
     * Additional metadata about the diagnostic.
     */
    tags?: DiagnosticTag[];
    /**
     * An array of related diagnostic information, e.g. when symbol-names within
     * a scope collide all definitions can be marked via this property.
     */
    relatedInformation?: DiagnosticRelatedInformation[];
}

We could from the types-converter convert fully, and only when it comes time to reviveMarker we update to ensure the types match.

[JonasHelming]

@EstFoisy Do you plan to look at the review comments?

[EstFoisy]

Hi @JonasHelming ,
Many thanks for advising. I was working with Vince for this PR and, from my understanding of the discussion I had with him, everything was ok and ready for this PR. I will look into it, try to fix the code to the best of my understanding, and see with him when he come back from vacation if all is good or if there is any further adjustment needed.

[JonasHelming]

@vince-fugnitto @EstFoisy : Maybe we could get this into the January release?

[vince-fugnitto]

LGTM 👍