API for hierarchical document symbol data

[jrieken]

In order to support a real outline view (#5605) and a breadcrumb bar (#9418, #31162) we need better document symbol information. Today, the API doesn't allow providers to return tree data and it also doesn't spec what the ranges of symbols should be. Some language extensions make the range be the whole symbol range, some make it the identifier range. It needs a new or refined API to support hierarchies, I see two options

• allow a tree of SymbolInformation-objects, e.g. add an optional children-property.
• have two range-objects on SymbolInformation-objects, one being the whole range and one being the identifier range. While this looks counter intuitive and worst than having tree-style-data it makes merging of different data sets from different providers easy.

[jrieken]

LSP side of this: microsoft/language-server-protocol#136

[Leedehai]

Indeed needed..

[jrieken]

We want to define, maybe propose, the API this milestone and build a UI for this in May.

[jrieken]

Proposal is to have a new type like DocumentSymbolInformation which has children and a symbol range. A DocumentSymbolProvider is free to return the new type, or old SymbolInformation objects. In the latter case, we cannot render a tree and because of that providers should signal what they return upon registration.

[eamodio]

FYI, this is also related to #11587

[jrieken]

First cut of the API proposal

export class HierarchicalSymbolInformation {
  name: string;
  kind: SymbolKind;
  location: Location; // use location#range to point to the 'identifier' or 'goto' position
  range: Range; // full symbol range as opposed
  children: HierarchicalSymbolInformation[]; // child items

  constructor(name: string, kind: SymbolKind, location: Location, range: Range);
}

export interface DocumentSymbolProvider {
  provideDocumentSymbols(document: TextDocument, token: CancellationToken): ProviderResult<HierarchicalSymbolInformation | SymbolInformation[]>;
}