All CLA requirements met.

@sandy081 @jrieken I'm still trying to understand the different aspects of this. I added MarkerTag like was done previously for Unnecessary but now that I re-read the proposal for #50972 I'm thinking that isn't needed because this won't be a marker (with a squiggly); it will somehow get tied to CompletionItem.deprecated or vice-versa. Basically somehow this will need to hint to style with a strike-through.

Am I understanding that correctly? If so, I can revert those two changes. Plus, limiting to just adding the new proposed enum member will be closer to the exact purpose of #56694

@kamranayub both requests, #56694 and #50972, are independent and need separate solutions. Having DiagnosticsTag.Deprecated will allow extensions to render certain diagnostics "special", e.g a common rendering of deprecated is a strikeout (in addition to the severity based rendering). Compare this to the faded rendering of unused/unnecessary code.

Thanks for clarifying. I will revert the two Marker changes.

I will revert the two Marker changes.

Not sure why you did that. Your change is now exposing a new enum member but it's not being used anywhere, e.g. it's not being translated into our "internal" API which is MarkerTag and it's not being read/used to apply any rendering tweaks

Ah, I assumed MarkerTag was specifically only for being able to render squigglies based on the usage I saw for MarkerTag.Unnecessary in 8bb27cd#diff-489874091c7caf27cd2ed52e59c41147

@jrieken Brought those changes back. Is the next step to try and perform some rendering using this new API or just add a test case for mapping the DiagnosticTag to MarkerTag?

perform some rendering using this new API or just ad

👍 the whole thing

Making progress.

Rendering CompletionItem.deprecated

Rendering MarkerTag.Deprecated

Both examples above are NOT actually implemented with the language provider, they are just hardcoded to include deprecated tag or set CompletionItem.deprecated so I could see the styling work.

diff --git a/extensions/typescript-language-features/src/features/completions.ts b/extensions/typescript-language-features/src/features/completions.ts
index fdfabd4365..89e80b8319 100644
--- a/extensions/typescript-language-features/src/features/completions.ts
+++ b/extensions/typescript-language-features/src/features/completions.ts
@@ -50,6 +50,9 @@ class MyCompletionItem extends vscode.CompletionItem {
        ) {
                super(tsEntry.name, MyCompletionItem.convertKind(tsEntry.kind));

+               // TODO: Remove
+               this.deprecated = true;
+
                if (tsEntry.source) {
                        // De-prioritze auto-imports
                        // https://github.com/Microsoft/vscode/issues/40311
diff --git a/extensions/typescript-language-features/src/typeScriptServiceClientHost.ts b/extensions/typescript-language-features/src/typeScriptServiceClientHost.ts
index 2571d395a5..7a88de73fe 100644
--- a/extensions/typescript-language-features/src/typeScriptServiceClientHost.ts
+++ b/extensions/typescript-language-features/src/typeScriptServiceClientHost.ts
@@ -261,6 +261,7 @@ export default class TypeScriptServiceClientHost extends Disposable {
                if (diagnostic.reportsUnnecessary) {
                        converted.tags = [vscode.DiagnosticTag.Unnecessary];
                }
+               converted.tags = [vscode.DiagnosticTag.Deprecated];
                (converted as vscode.Diagnostic & { reportUnnecessary: any }).reportUnnecessary = diagnostic.reportsUnnecessary;
                return converted as vscode.Diagnostic & { reportUnnecessary: any };
        }

Please do not mix both features into one PR, please extract the changes for the completion item into a separate PR. Thanks

@kamranayub fyi - I have moved the completion related commits into https://github.com/microsoft/vscode/tree/joh/completionsDeprecated. There is some little work left there and I would appreciate another PR off that

This works like a charm. Thanks @kamranayub

Merged despite an open question regarding the use of both tags, today deprecated will overrule unnecessary. Let's wait for the bug