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 +2690,64 @@ fn foldingRangeHandler(server: *Server, writer: anytype, id: types.RequestId, re
     });
 }
 
+fn selectionRangeHandler(server: *Server, writer: anytype, id: types.RequestId, req: requests.SelectionRange) !void {
+    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);
+    };
+
+    // For each of the input positons, we need to compute the stack of AST
+    // nodes/ranges which contain the position. At the moment, we do this in a
+    // super inefficient way, by iterationg _all_ nodes, selecting the ones that
+    // contain position, and then sorting.
+    //
+    // A faster algorithm would be to walk the tree starting from the root,
+    // descending into the child containing the position at every step.
+    var result = try allocator.alloc(*types.SelectionRange, req.params.positions.len);
+    var locs = try std.ArrayListUnmanaged(offsets.Loc).initCapacity(allocator, 32);
+    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(offsets.Loc, locs.items, {}, shorterLocsFirst);
+        {
+            var i: usize = 0;
+            while (i + 1 < locs.items.len) {
+                if (std.meta.eql(locs.items[i], locs.items[i + 1])) {
+                    _ = locs.orderedRemove(i);
+                } else {
+                    i += 1;
+                }
+            }
+        }
+
+        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 shorterLocsFirst(_: void, lhs: offsets.Loc, rhs: offsets.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 +2894,7 @@ 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 {
@@ -528,3 +529,8 @@ pub const FoldingRange = struct {
     startLine: usize,
     endLine: usize,
 };
+
+pub const SelectionRange = struct {
+    range: Range,
+    parent: ?*SelectionRange,
+};

tests/lsp_features/selection_range.zig

@@ -0,0 +1,76 @@
+const std = @import("std");
+const zls = @import("zls");
+const builtin = @import("builtin");
+
+const helper = @import("../helper.zig");
+const Context = @import("../context.zig").Context;
+const ErrorBuilder = @import("../ErrorBuilder.zig");
+
+const types = zls.types;
+const offsets = zls.offsets;
+const requests = zls.requests;
+
+const allocator: std.mem.Allocator = std.testing.allocator;
+
+test "selectionRange - empty" {
+    try testSelectionRange("<>", &.{});
+}
+
+test "seletionRange - smoke" {
+    try testSelectionRange(
+        \\fn main() void {
+        \\    const x = 1 <>+ 1;
+        \\}
+    , &.{ "1 + 1", "const x = 1 + 1", "{\n    const x = 1 + 1;\n}" });
+}
+
+fn testSelectionRange(source: []const u8, want: []const []const u8) !void {
+    var phr = try helper.collectClearPlaceholders(allocator, source);
+    defer phr.deinit(allocator);
+
+    var ctx = try Context.init();
+    defer ctx.deinit();
+
+    const test_uri: []const u8 = switch (builtin.os.tag) {
+        .windows => "file:///C:\\test.zig",
+        else => "file:///test.zig",
+    };
+
+    try ctx.requestDidOpen(test_uri, phr.new_source);
+
+    const position = offsets.locToRange(phr.new_source, phr.locations.items(.new)[0], .utf16).start;
+
+    const SelectionRange = struct {
+        range: types.Range,
+        parent: ?*@This(),
+    };
+
+    const request = requests.SelectionRange{ .params = .{
+        .textDocument = .{ .uri = test_uri },
+        .positions = &.{position},
+    } };
+
+    const response = try ctx.requestGetResponse(?[]SelectionRange, "textDocument/selectionRange", request);
+    defer response.deinit();
+
+    const selectionRanges: []SelectionRange = response.result orelse {
+        std.debug.print("Server returned `null` as the result\n", .{});
+        return error.InvalidResponse;
+    };
+
+    var got = std.ArrayList([]const u8).init(allocator);
+    defer got.deinit();
+
+    var it: ?*SelectionRange = &selectionRanges[0];
+    while (it) |r| {
+        const slice = offsets.rangeToSlice(phr.new_source, r.range, .utf16);
+        (try got.addOne()).* = slice;
+        it = r.parent;
+    }
+    const last = got.pop();
+    try std.testing.expectEqualStrings(phr.new_source, last);
+    try std.testing.expectEqual(want.len, got.items.len);
+    for (want) |w, i| {
+        try std.testing.expectEqualStrings(w, got.items[i]);
+    }
+}

tests/tests.zig

@@ -14,6 +14,7 @@ comptime {
     _ = @import("lsp_features/inlay_hints.zig");
     _ = @import("lsp_features/references.zig");
     _ = @import("lsp_features/completion.zig");
+    _ = @import("lsp_features/selection_range.zig");
 
     // Language features
     _ = @import("language_features/cimport.zig");