Investigate eagerly returning more information about suggestions

Problem

Suggestions VS Code have three broad UX parts:

• Name/label. Primary identifier for a suggestion, such as foo.
• Details. Type information or auto import info, such as string.
• Documentation. Js doc info and additional details about the suggestion item

Currently VS Code only shows the details of the currently active suggestion. This can be problematic in cases like auto imports, where multiple symbols may all have the same name:

This design also reflects the design of the suggestion api:

• completionInfo returns the entire list of suggestions, but only includes the name
• completionEntryDetails returns the details and documentation for an individual suggestion

Investigation

With https://github.com/microsoft/vscode/issues/39441, VS Code is exploring letting languages/extensions return the details part of the suggestion eagerly. This would let VS Code show details for the entire list of suggestions instead of just for the active one. In the auto import case specifically, this would likely mean showing the file paths we would import from.

We would like the typescript team's feedback on these idea and our current proposals:

• What information would be most helpful to render in the main suggestion list?
• How much overhead would returning this information add? Both in terms of message size and TS server computation time?

/cc @jrieken For VS Code apis
/cc @amcasey @minestarks for VS

Start by reading this issue and the linked VS Code issue #39441, then compare the completionInfo and completionEntryDetails APIs described here. Investigate which suggestion details would be useful in the main list and the message-size and TypeScript server computation costs. Done means documenting the TypeScript team's feedback or reaching a clear proposal.