textDocument/selectionRange

closes #777

src/Server.zig

@@ -1662,7 +1662,7 @@ fn initializeHandler(server: *Server, writer: anytype, id: types.RequestId, req:
                     .documentFormattingProvider = true,
                     .documentRangeFormattingProvider = false,
                     .foldingRangeProvider = true,
-                    .selectionRangeProvider = false,
+                    .selectionRangeProvider = true,
                     .workspaceSymbolProvider = false,
                     .rangeProvider = false,
                     .documentProvider = true,
@@ -2690,6 +2690,49 @@ fn foldingRangeHandler(server: *Server, writer: anytype, id: types.RequestId, re
     });
 }
 
+fn selectionRangeHandler(server: *Server, writer: anytype, id: types.RequestId, req: requests.SelectionRange) !void {
+    const Loc = std.zig.Token.Loc;
+
+    const allocator = server.arena.allocator();
+    const handle = server.document_store.getHandle(req.params.textDocument.uri) orelse {
+        log.warn("Trying to get selection range of non existent document {s}", .{req.params.textDocument.uri});
+        return try respondGeneric(writer, id, null_result_response);
+    };
+
+    var result = try allocator.alloc(*types.SelectionRange, req.params.positions.len);
+    var locs = try std.ArrayListUnmanaged(Loc).initCapacity(allocator, 8);
+    for (req.params.positions) |position, position_index| {
+        const index = offsets.positionToIndex(handle.text, position, server.offset_encoding);
+
+        locs.clearRetainingCapacity();
+        for (handle.tree.nodes.items(.data)) |_, i| {
+            const node = @intCast(u32, i);
+            const loc = offsets.nodeToLoc(handle.tree, node);
+            if (loc.start <= index and index <= loc.end) {
+                (try locs.addOne(allocator)).* = loc;
+            }
+        }
+
+        std.sort.sort(Loc, locs.items, {}, locLessThan);
+
+        var selection_ranges = try allocator.alloc(types.SelectionRange, locs.items.len);
+        for (selection_ranges) |*range, i| {
+            range.range = offsets.locToRange(handle.text, locs.items[i], server.offset_encoding);
+            range.parent = if (i + 1 < selection_ranges.len) &selection_ranges[i + 1] else null;
+        }
+        result[position_index] = &selection_ranges[0];
+    }
+
+    try send(writer, allocator, types.Response{
+        .id = id,
+        .result = .{ .SelectionRange = result },
+    });
+}
+
+fn locLessThan(_: void, lhs: std.zig.Token.Loc, rhs: std.zig.Token.Loc) bool {
+    return (lhs.end - lhs.start) < (rhs.end - rhs.start);
+}
+
 // Needed for the hack seen below.
 fn extractErr(val: anytype) anyerror {
     val catch |e| return e;
@@ -2836,6 +2879,7 @@ pub fn processJsonRpc(server: *Server, writer: anytype, json: []const u8) !void
         .{ "textDocument/codeAction", requests.CodeAction, codeActionHandler },
         .{ "workspace/didChangeConfiguration", Config.DidChangeConfigurationParams, didChangeConfigurationHandler },
         .{ "textDocument/foldingRange", requests.FoldingRange, foldingRangeHandler },
+        .{ "textDocument/selectionRange", requests.SelectionRange, selectionRangeHandler },
     };
 
     if (zig_builtin.zig_backend == .stage1) {

src/requests.zig

@@ -312,3 +312,10 @@ pub const FoldingRange = struct {
         textDocument: TextDocumentIdentifier,
     },
 };
+
+pub const SelectionRange = struct {
+    params: struct {
+        textDocument: TextDocumentIdentifier,
+        positions: []types.Position,
+    },
+};

src/types.zig

@@ -44,6 +44,7 @@ pub const ResponseParams = union(enum) {
     CodeAction: []CodeAction,
     ApplyEdit: ApplyWorkspaceEditParams,
     FoldingRange: []FoldingRange,
+    SelectionRange: []*SelectionRange,
 };
 
 pub const Response = struct {
@@ -525,6 +526,11 @@ pub const DocumentHighlight = struct {
 };
 
 pub const FoldingRange = struct {
-    startLine: usize, 
+    startLine: usize,
     endLine: usize,
 };
+
+pub const SelectionRange = struct {
+    range: Range,
+    parent: ?*SelectionRange,
+};