Testing improvements (#662)

build.zig

@@ -117,8 +117,6 @@ pub fn build(b: *std.build.Builder) !void {
     var tests = b.addTest("tests/tests.zig");
     tests.use_stage1 = true;
     tests.addPackage(.{ .name = "zls", .source = .{ .path = "src/zls.zig" }, .dependencies = exe.packages.items });
-    tests.addPackage(.{ .name = "helper", .source = .{ .path = "tests/helper.zig" } });
-    tests.addPackage(.{ .name = "context", .source = .{ .path = "tests/context.zig" } });
     tests.setBuildMode(.Debug);
     tests.setTarget(target);
     test_step.dependOn(&tests.step);

src/offsets.zig

@@ -94,10 +94,7 @@ pub fn tokenLength(tree: Ast, token_index: Ast.TokenIndex, encoding: Encoding) u
 }
 
 pub fn rangeLength(text: []const u8, range: types.Range, encoding: Encoding) usize {
-    const loc: Loc = .{
+    const loc = rangeToLoc(text, range, encoding);
-        .start = positionToIndex(text, range.start, encoding),
-        .end = positionToIndex(text, range.end, encoding),
-    };
     return locLength(text, loc, encoding);
 }
 
@@ -163,6 +160,17 @@ pub fn locToRange(text: []const u8, loc: Loc, encoding: Encoding) types.Range {
     };
 }
 
+pub fn rangeToSlice(text: []const u8, range: types.Range, encodig: Encoding) []const u8 {
+    return locToSlice(text, rangeToLoc(text, range, encodig));
+}
+
+pub fn rangeToLoc(text: []const u8, range: types.Range, encodig: Encoding) Loc {
+    return .{
+        .start = positionToIndex(text, range.start, encodig),
+        .end = positionToIndex(text, range.end, encodig),
+    };
+}
+
 pub fn nodeToLoc(tree: Ast, node: Ast.Node.Index) Loc {
     return .{ .start = tokenToIndex(tree, tree.firstToken(node)), .end = tokenToLoc(tree, ast.lastToken(tree, node)).end };
 }

src/references.zig

@@ -516,7 +516,7 @@ pub fn symbolReferences(
                 try imports.resize(arena.allocator(), 0);
             }
         },
-        .param_decl => |param| {
+        .param_decl => |param| blk: {
             // Rename the param tok.
             for (curr_handle.document_scope.scopes.items) |scope| {
                 if (scope.data != .function) continue;
@@ -530,9 +530,9 @@ pub fn symbolReferences(
                 while (ast.nextFnParam(&it)) |candidate| {
                     if (!std.meta.eql(candidate, param)) continue;
 
-                    if (curr_handle.tree.nodes.items(.tag)[proto] != .fn_decl) break;
+                    if (curr_handle.tree.nodes.items(.tag)[proto] != .fn_decl) break :blk;
                     try symbolReferencesInternal(&builder, curr_handle.tree.nodes.items(.data)[proto].rhs, curr_handle);
-                    break;
+                    break :blk;
                 }
             }
             log.warn("Could not find param decl's function", .{});

tests/ErrorBuilder.zig

@@ -0,0 +1,99 @@
+const std = @import("std");
+
+const zls = @import("zls");
+
+const offsets = zls.offsets;
+
+const ErrorBuilder = @This();
+
+allocator: std.mem.Allocator,
+items: std.ArrayListUnmanaged(MsgItem) = .{},
+source: []const u8,
+
+pub fn init(allocator: std.mem.Allocator, source: []const u8) ErrorBuilder {
+    return ErrorBuilder{
+        .allocator = allocator,
+        .source = source,
+    };
+}
+
+pub fn deinit(builder: *ErrorBuilder) void {
+    for (builder.items.items) |item| {
+        builder.allocator.free(item.message);
+    }
+    builder.items.deinit(builder.allocator);
+}
+
+pub fn msgAtLoc(builder: *ErrorBuilder, comptime fmt: []const u8, loc: offsets.Loc, level: std.log.Level, args: anytype) !void {
+    try builder.items.append(builder.allocator, .{
+        .loc = loc,
+        .level = level,
+        .message = try std.fmt.allocPrint(builder.allocator, fmt, args),
+    });
+}
+
+pub fn msgAtIndex(builder: *ErrorBuilder, comptime fmt: []const u8, index: usize, level: std.log.Level, args: anytype) !void {
+    return msgAtLoc(builder, fmt, .{ .start = index, .end = index }, level, args);
+}
+
+pub fn hasMessages(builder: *ErrorBuilder) bool {
+    return builder.items.items.len != 0;
+}
+
+pub fn write(builder: *ErrorBuilder, writer: anytype) !void {
+    if (!builder.hasMessages()) return;
+
+    std.sort.sort(MsgItem, builder.items.items, builder, ErrorBuilder.lessThan);
+
+    try writer.writeByte('\n');
+
+    var start: usize = 0;
+    for (builder.items.items) |item| {
+        const line = offsets.lineLocAtIndex(builder.source, item.loc.start);
+        defer start = line.end;
+
+        try writer.writeAll(builder.source[start..line.end]);
+        try writer.writeByte('\n');
+        {
+            var i: usize = line.start;
+            while (i < item.loc.start) : (i += 1) try writer.writeByte(' ');
+            while (i < item.loc.end) : (i += 1) try writer.writeByte('^');
+            if (item.loc.start == item.loc.end) try writer.writeByte('^');
+        }
+        const level_txt: []const u8 = switch (item.level) {
+            .err => "error",
+            .warn => "warning",
+            .info => "info",
+            .debug => "debug",
+        };
+        try writer.print(" {s}: {s}", .{ level_txt, item.message });
+    }
+
+    try writer.writeAll(builder.source[start..builder.source.len]);
+    try writer.writeByte('\n');
+}
+
+pub fn writeDebug(builder: *ErrorBuilder) void {
+    if (!builder.hasMessages()) return;
+    std.debug.getStderrMutex().lock();
+    defer std.debug.getStderrMutex().unlock();
+    nosuspend builder.write(std.io.getStdErr().writer()) catch return;
+}
+
+const MsgItem = struct {
+    loc: offsets.Loc,
+    level: std.log.Level,
+    message: []const u8,
+};
+
+fn lessThan(builder: *ErrorBuilder, lhs: MsgItem, rhs: MsgItem) bool {
+    const is_less = lhs.loc.start < rhs.loc.start;
+    const text = if (is_less) builder.source[lhs.loc.start..rhs.loc.start] else builder.source[rhs.loc.start..lhs.loc.start];
+
+    // report messages on the same line in reverse order
+    if (std.mem.indexOfScalar(u8, text, '\n') == null) {
+        return !is_less;
+    }
+
+    return is_less;
+}

tests/context.zig

@@ -3,6 +3,8 @@ const zls = @import("zls");
 
 const headerPkg = zls.header;
 const Server = zls.Server;
+const types = zls.types;
+const requests = zls.requests;
 
 const initialize_msg =
     \\{"processId":6896,"clientInfo":{"name":"vscode","version":"1.46.1"},"rootPath":null,"rootUri":null,"capabilities":{"workspace":{"applyEdit":true,"workspaceEdit":{"documentChanges":true,"resourceOperations":["create","rename","delete"],"failureHandling":"textOnlyTransactional"},"didChangeConfiguration":{"dynamicRegistration":true},"didChangeWatchedFiles":{"dynamicRegistration":true},"symbol":{"dynamicRegistration":true,"symbolKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]},"tagSupport":{"valueSet":[1]}},"executeCommand":{"dynamicRegistration":true},"configuration":true,"workspaceFolders":true},"textDocument":{"publishDiagnostics":{"relatedInformation":true,"versionSupport":false,"tagSupport":{"valueSet":[1,2]},"complexDiagnosticCodeSupport":true},"synchronization":{"dynamicRegistration":true,"willSave":true,"willSaveWaitUntil":true,"didSave":true},"completion":{"dynamicRegistration":true,"contextSupport":true,"completionItem":{"snippetSupport":true,"commitCharactersSupport":true,"documentationFormat":["markdown","plaintext"],"deprecatedSupport":true,"preselectSupport":true,"tagSupport":{"valueSet":[1]},"insertReplaceSupport":true},"completionItemKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]}},"hover":{"dynamicRegistration":true,"contentFormat":["markdown","plaintext"]},"signatureHelp":{"dynamicRegistration":true,"signatureInformation":{"documentationFormat":["markdown","plaintext"],"parameterInformation":{"labelOffsetSupport":true}},"contextSupport":true},"definition":{"dynamicRegistration":true,"linkSupport":true},"references":{"dynamicRegistration":true},"documentHighlight":{"dynamicRegistration":true},"documentSymbol":{"dynamicRegistration":true,"symbolKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]},"hierarchicalDocumentSymbolSupport":true,"tagSupport":{"valueSet":[1]}},"codeAction":{"dynamicRegistration":true,"isPreferredSupport":true,"codeActionLiteralSupport":{"codeActionKind":{"valueSet":["","quickfix","refactor","refactor.extract","refactor.inline","refactor.rewrite","source","source.organizeImports"]}}},"codeLens":{"dynamicRegistration":true},"formatting":{"dynamicRegistration":true},"rangeFormatting":{"dynamicRegistration":true},"onTypeFormatting":{"dynamicRegistration":true},"rename":{"dynamicRegistration":true,"prepareSupport":true},"documentLink":{"dynamicRegistration":true,"tooltipSupport":true},"typeDefinition":{"dynamicRegistration":true,"linkSupport":true},"implementation":{"dynamicRegistration":true,"linkSupport":true},"colorProvider":{"dynamicRegistration":true},"foldingRange":{"dynamicRegistration":true,"rangeLimit":5000,"lineFoldingOnly":true},"declaration":{"dynamicRegistration":true,"linkSupport":true},"selectionRange":{"dynamicRegistration":true},"semanticTokens":{"dynamicRegistration":true,"tokenTypes":["comment","keyword","number","regexp","operator","namespace","type","struct","class","interface","enum","typeParameter","function","member","macro","variable","parameter","property","label"],"tokenModifiers":["declaration","documentation","static","abstract","deprecated","readonly"]}},"window":{"workDoneProgress":true}},"trace":"off","workspaceFolders":[{"uri":"file://./tests", "name":"root"}]}
@@ -101,4 +103,58 @@ pub const Context = struct {
 
         try std.testing.expectEqualStrings(expected, result_json);
     }
+
+    // helper
+    pub fn requestDidOpen(self: *Context, uri: []const u8, source: []const u8) !void {
+        const open_document = requests.OpenDocument{
+            .params = .{
+                .textDocument = .{
+                    .uri = uri,
+                    // .languageId = "zig",
+                    // .version = 420,
+                    .text = source,
+                },
+            },
+        };
+        const params = try std.json.stringifyAlloc(allocator, open_document.params, .{});
+        defer allocator.free(params);
+        try self.request("textDocument/didOpen", params, null);
+    }
+
+    pub fn Response(comptime Result: type) type {
+        return struct {
+            jsonrpc: []const u8,
+            id: types.RequestId,
+            result: Result,
+
+            pub fn deinit(self: @This()) void {
+                const parse_options = std.json.ParseOptions{
+                    .allocator = allocator,
+                    .ignore_unknown_fields = true,
+                };
+                std.json.parseFree(@This(), self, parse_options);
+            }
+        };
+    }
+
+    pub fn requestGetResponse(self: *Context, comptime Result: type, method: []const u8, request_struct: anytype) !Response(Result) {
+        const params = try std.json.stringifyAlloc(allocator, request_struct.params, .{});
+        defer allocator.free(params);
+
+        const response_bytes = try self.requestAlloc(method, params);
+        defer allocator.free(response_bytes);
+
+        const parse_options = std.json.ParseOptions{
+            .allocator = allocator,
+            .ignore_unknown_fields = true,
+        };
+
+        var token_stream = std.json.TokenStream.init(response_bytes);
+        const response = try std.json.parse(Response(Result), &token_stream, parse_options);
+        errdefer std.json.parseFree(Response(Result), response, parse_options);
+
+        // TODO validate jsonrpc and id
+
+        return response;
+    }
 };

tests/helper.zig

@@ -1,73 +1,75 @@
 const std = @import("std");
+const zls = @import("zls");
 
-pub const Placeholder = struct {
+const offsets = zls.offsets;
-    loc: Loc,
-
-    pub const Loc = std.zig.Token.Loc;
-
-    pub fn placeholderSlice(self: Placeholder, source: []const u8) []const u8 {
-        return source[self.loc.start..self.loc.end];
-    }
-};
 
 /// returns an array of all placeholder locations
-pub fn collectPlaceholder(allocator: std.mem.Allocator, source: []const u8) ![]Placeholder {
+pub fn collectPlaceholderLocs(allocator: std.mem.Allocator, source: []const u8) ![]offsets.Loc {
-    var placeholders = std.ArrayListUnmanaged(Placeholder){};
+    var locations = std.ArrayListUnmanaged(offsets.Loc){};
-    errdefer placeholders.deinit(allocator);
+    errdefer locations.deinit(allocator);
 
     var source_index: usize = 0;
     while (std.mem.indexOfScalarPos(u8, source, source_index, '<')) |start_index| {
-        const end_index = std.mem.indexOfScalarPos(u8, source, start_index + 1, '>') orelse return error.Invalid;
+        const end_index = 1 + (std.mem.indexOfScalarPos(u8, source, start_index + 1, '>') orelse return error.Invalid);
 
-        try placeholders.append(allocator, .{ .loc = .{
+        try locations.append(allocator, .{
             .start = start_index,
             .end = end_index,
-        } });
+        });
 
-        source_index = end_index + 1;
+        source_index = end_index;
     }
 
-    return placeholders.toOwnedSlice(allocator);
+    return locations.toOwnedSlice(allocator);
 }
 
-/// returns `source` without any placeholders
+/// returns `source` where every placeholder is replaced with `new_name`
-pub fn clearPlaceholders(allocator: std.mem.Allocator, source: []const u8) ![]const u8 {
+pub fn replacePlaceholders(allocator: std.mem.Allocator, source: []const u8, new_name: []const u8) ![]const u8 {
     var output = std.ArrayListUnmanaged(u8){};
     errdefer output.deinit(allocator);
 
     var source_index: usize = 0;
     while (std.mem.indexOfScalarPos(u8, source, source_index, '<')) |start_index| {
         try output.appendSlice(allocator, source[source_index..start_index]);
+        try output.appendSlice(allocator, new_name);
 
-        source_index = std.mem.indexOfScalarPos(u8, source, start_index + 1, '>') orelse return error.Invalid;
+        source_index = 1 + (std.mem.indexOfScalarPos(u8, source, start_index + 1, '>') orelse return error.Invalid);
-        source_index += 1;
     }
     try output.appendSlice(allocator, source[source_index..source.len]);
 
     return output.toOwnedSlice(allocator);
 }
 
-const CollectClearPlaceholdersResult = struct {
+/// returns `source` without any placeholders
-    /// placeholders relative to the `source` parameter in `collectClearPlaceholders`
+pub fn clearPlaceholders(allocator: std.mem.Allocator, source: []const u8) ![]const u8 {
-    placeholders: []Placeholder,
+    return replacePlaceholders(allocator, source, "");
-    /// placeholders locations to `source`
+}
-    placeholder_locations: []usize,
-    /// source without any placeholders
-    source: []const u8,
 
-    pub fn deinit(self: @This(), allocator: std.mem.Allocator) void {
+const CollectPlaceholdersResult = struct {
-        allocator.free(self.placeholders);
+    /// list of all placeholder with old and new location
-        allocator.free(self.placeholder_locations);
+    locations: std.MultiArrayList(LocPair),
-        allocator.free(self.source);
+    /// equivalent to calling `replacePlaceholders(source, new_name)`
+    new_source: []const u8,
+
+    pub const LocPair = struct {
+        /// placeholder location relative to the `source` parameter
+        old: offsets.Loc,
+        /// placeholder location relative to `new_source`
+        new: offsets.Loc,
+    };
+
+    pub fn deinit(self: *@This(), allocator: std.mem.Allocator) void {
+        self.locations.deinit(allocator);
+        allocator.free(self.new_source);
     }
 };
 
-/// see `CollectClearPlaceholdersResult`
+pub fn collectClearPlaceholders(allocator: std.mem.Allocator, source: []const u8) !CollectPlaceholdersResult {
-pub fn collectClearPlaceholders(allocator: std.mem.Allocator, source: []const u8) !CollectClearPlaceholdersResult {
+    return collectReplacePlaceholders(allocator, source, "");
-    var placeholders = std.ArrayListUnmanaged(Placeholder){};
+}
-    errdefer placeholders.deinit(allocator);
 
-    var locations = std.ArrayListUnmanaged(usize){};
+pub fn collectReplacePlaceholders(allocator: std.mem.Allocator, source: []const u8, new_name: []const u8) !CollectPlaceholdersResult {
+    var locations = std.MultiArrayList(CollectPlaceholdersResult.LocPair){};
     errdefer locations.deinit(allocator);
 
     var new_source = std.ArrayListUnmanaged(u8){};
@@ -76,27 +78,84 @@ pub fn collectClearPlaceholders(allocator: std.mem.Allocator, source: []const u8
     var source_index: usize = 0;
     var new_source_index: usize = 0;
     while (std.mem.indexOfScalarPos(u8, source, source_index, '<')) |start_index| {
-        const end_index = std.mem.indexOfScalarPos(u8, source, start_index + 1, '>') orelse return error.Invalid;
+        const end_index = 1 + (std.mem.indexOfScalarPos(u8, source, start_index + 1, '>') orelse return error.Invalid);
 
-        const placeholder = Placeholder{ .loc = .{
+        const old_loc: offsets.Loc = .{
-            .start = start_index + 1,
+            .start = start_index,
             .end = end_index,
-        } };
+        };
+        defer source_index = old_loc.end;
 
-        try placeholders.append(allocator, placeholder);
+        const text = source[source_index..start_index];
 
-        new_source_index = new_source_index + (start_index - source_index);
+        const new_loc: offsets.Loc = .{
-        try locations.append(allocator, new_source_index);
+            .start = new_source_index + text.len,
-        try new_source.appendSlice(allocator, source[source_index..start_index]);
+            .end = new_source_index + text.len + new_name.len,
+        };
+        defer new_source_index = new_loc.end;
 
-        source_index = end_index + 1;
+        try locations.append(allocator, .{
+            .old = old_loc,
+            .new = new_loc,
+        });
+        try new_source.appendSlice(allocator, text);
+        try new_source.appendSlice(allocator, new_name);
     }
     try new_source.appendSlice(allocator, source[source_index..source.len]);
 
-    return CollectClearPlaceholdersResult{
+    return CollectPlaceholdersResult{
-        .placeholders = placeholders.toOwnedSlice(allocator),
+        .locations = locations,
-        .placeholder_locations = locations.toOwnedSlice(allocator),
+        .new_source = new_source.toOwnedSlice(allocator),
-        .source = new_source.toOwnedSlice(allocator),
     };
 }
 
+fn testCollectReplacePlaceholders(
+    source: []const u8,
+    expected_source: []const u8,
+    expected_old_locs: []const offsets.Loc,
+    expected_new_locs: []const offsets.Loc,
+) !void {
+    const allocator = std.testing.allocator;
+    const new_name = "foo";
+
+    var result = try collectReplacePlaceholders(allocator, source, new_name);
+    defer result.deinit(allocator);
+
+    const expected_old_locs2 = try collectPlaceholderLocs(allocator, source);
+    defer allocator.free(expected_old_locs2);
+
+    const expected_source2 = try replacePlaceholders(allocator, source, new_name);
+    defer allocator.free(expected_source2);
+
+    try std.testing.expectEqualStrings(expected_source, expected_source2);
+    try std.testing.expectEqualSlices(offsets.Loc, expected_old_locs, expected_old_locs2);
+
+    try std.testing.expectEqualStrings(expected_source, result.new_source);
+    try std.testing.expectEqualSlices(offsets.Loc, expected_old_locs, result.locations.items(.old));
+    try std.testing.expectEqualSlices(offsets.Loc, expected_new_locs, result.locations.items(.new));
+}
+
+test "helper - collectReplacePlaceholders" {
+    try testCollectReplacePlaceholders("", "", &.{}, &.{});
+    try testCollectReplacePlaceholders("text", "text", &.{}, &.{});
+
+    try testCollectReplacePlaceholders("<>", "foo", &.{
+        .{ .start = 0, .end = 2 },
+    }, &.{
+        .{ .start = 0, .end = 3 },
+    });
+
+    try testCollectReplacePlaceholders("a<>b", "afoob", &.{
+        .{ .start = 1, .end = 3 },
+    }, &.{
+        .{ .start = 1, .end = 4 },
+    });
+
+    try testCollectReplacePlaceholders("<><>", "foofoo", &.{
+        .{ .start = 0, .end = 2 },
+        .{ .start = 2, .end = 4 },
+    }, &.{
+        .{ .start = 0, .end = 3 },
+        .{ .start = 3, .end = 6 },
+    });
+}

tests/lsp_features/inlay_hints.zig

@@ -1,8 +1,9 @@
 const std = @import("std");
 const zls = @import("zls");
 
-const helper = @import("helper");
+const helper = @import("../helper.zig");
-const Context = @import("context").Context;
+const Context = @import("../context.zig").Context;
+const ErrorBuilder = @import("../ErrorBuilder.zig");
 
 const types = zls.types;
 const offsets = zls.offsets;
@@ -66,84 +67,70 @@ test "inlayhints - builtin call" {
 }
 
 fn testInlayHints(source: []const u8) !void {
-    const phr = try helper.collectClearPlaceholders(allocator, source);
+    var phr = try helper.collectClearPlaceholders(allocator, source);
     defer phr.deinit(allocator);
 
     var ctx = try Context.init();
     defer ctx.deinit();
 
-    const open_document = requests.OpenDocument{
+    try ctx.requestDidOpen("file:///test.zig", phr.new_source);
-        .params = .{
-            .textDocument = .{
-                .uri = "file:///test.zig",
-                // .languageId = "zig",
-                // .version = 420,
-                .text = phr.source,
-            },
-        },
-    };
-
-    const did_open_method = try std.json.stringifyAlloc(allocator, open_document.params, .{});
-    defer allocator.free(did_open_method);
-
-    try ctx.request("textDocument/didOpen", did_open_method, null);
 
     const range = types.Range{
         .start = types.Position{ .line = 0, .character = 0 },
-        .end = offsets.indexToPosition(phr.source, phr.source.len, .utf16),
+        .end = offsets.indexToPosition(phr.new_source, phr.new_source.len, .utf16),
     };
 
-    const method = try std.json.stringifyAlloc(allocator, .{
-        .textDocument = .{
-            .uri = "file:///test.zig",
-        },
-        .range = range,
-    }, .{});
-    defer allocator.free(method);
-
-    const response_bytes = try ctx.requestAlloc("textDocument/inlayHint", method);
-    defer allocator.free(response_bytes);
-
     const InlayHint = struct {
         position: types.Position,
         label: []const u8,
         kind: types.InlayHintKind,
     };
 
-    const Response = struct {
+    const request = requests.InlayHint{
-        jsonrpc: []const u8,
+        .params = .{
-        id: types.RequestId,
+            .textDocument = .{ .uri = "file:///test.zig" },
-        result: []InlayHint,
+            .range = range,
+        },
     };
 
-    const parse_options = std.json.ParseOptions{
+    const response = try ctx.requestGetResponse(?[]InlayHint, "textDocument/inlayHint", request);
-        .allocator = allocator,
+    defer response.deinit();
-        .ignore_unknown_fields = true,
+
+    const hints: []InlayHint = response.result orelse {
+        std.debug.print("Server returned `null` as the result\n", .{});
+        return error.InvalidResponse;
     };
-    var token_stream = std.json.TokenStream.init(response_bytes);
-    var response = try std.json.parse(Response, &token_stream, parse_options);
-    defer std.json.parseFree(Response, response, parse_options);
 
-    const hints = response.result;
+    var error_builder = ErrorBuilder.init(allocator, phr.new_source);
+    defer error_builder.deinit();
+    errdefer error_builder.writeDebug();
 
-    try std.testing.expectEqual(phr.placeholder_locations.len, hints.len);
+    var i: usize = 0;
+    outer: while (i < phr.locations.len) : (i += 1) {
+        const old_loc = phr.locations.items(.old)[i];
+        const new_loc = phr.locations.items(.new)[i];
 
-    outer: for (phr.placeholder_locations) |loc, i| {
+        const expected_name = offsets.locToSlice(source, old_loc);
-        const name = phr.placeholders[i].placeholderSlice(source);
+        const expected_label = expected_name[1 .. expected_name.len - 1]; // convert <name> to name
 
-        const position = offsets.indexToPosition(phr.source, loc, .utf16);
+        const position = offsets.indexToPosition(phr.new_source, new_loc.start, ctx.server.offset_encoding);
 
         for (hints) |hint| {
             if (position.line != hint.position.line or position.character != hint.position.character) continue;
+            
+            const actual_label = hint.label[0 .. hint.label.len - 1]; // exclude :
 
-            try std.testing.expect(hint.label.len != 0);
+            if (!std.mem.eql(u8, expected_label, actual_label)) {
-            const trimmedLabel = hint.label[0 .. hint.label.len - 1]; // exclude :
+                try error_builder.msgAtLoc("expected label `{s}` here but got `{s}`!", new_loc, .err, .{ expected_label, actual_label });
-            try std.testing.expectEqualStrings(name, trimmedLabel);
+            }
-            try std.testing.expectEqual(types.InlayHintKind.Parameter, hint.kind);
+            if (hint.kind != types.InlayHintKind.Parameter) {
+                try error_builder.msgAtLoc("hint kind should be `{s}` but got `{s}`!", new_loc, .err, .{ @tagName(types.InlayHintKind.Parameter), @tagName(hint.kind) });
+            }
 
             continue :outer;
         }
-        std.debug.print("Placeholder '{s}' at {}:{} (line:colon) not found!", .{ name, position.line, position.character });
+        try error_builder.msgAtLoc("expected hint `{s}` here", new_loc, .err, .{expected_label});
-        return error.PlaceholderNotFound;
     }
+
+    if (error_builder.hasMessages()) return error.InvalidResponse;
 }

tests/lsp_features/references.zig

@@ -0,0 +1,189 @@
+const std = @import("std");
+const zls = @import("zls");
+
+const helper = @import("../helper.zig");
+const Context = @import("../context.zig").Context;
+const ErrorBuilder = @import("../ErrorBuilder.zig");
+
+const types = zls.types;
+const requests = zls.requests;
+const offsets = zls.offsets;
+
+const allocator: std.mem.Allocator = std.testing.allocator;
+
+// TODO fix references so that we can stop skipping these tests
+const skip_references_tests = true;
+
+test "references" {
+    if (skip_references_tests) return error.SkipZigTest;
+    try testReferences(
+        \\const <0> = 0;
+        \\const foo = <0>;
+    );
+    try testReferences(
+        \\var <0> = 0;
+        \\var foo = <0>;
+    );
+    try testReferences(
+        \\const <0> = struct {};
+        \\var foo: <0> = <0>{};
+    );
+    try testReferences(
+        \\const <0> = enum {};
+        \\var foo: <0> = undefined;
+    );
+    try testReferences(
+        \\const <0> = union {};
+        \\var foo: <0> = <0>{};
+    );
+    try testReferences(
+        \\fn <0>() void {}
+        \\var foo = <0>();
+    );
+    try testReferences(
+        \\const <0> = error{};
+        \\fn bar() <0>!void {}
+    );
+}
+
+test "references - global scope" {
+    if (skip_references_tests) return error.SkipZigTest;
+    try testReferences(
+        \\const foo = <0>;
+        \\const <0> = 0;
+        \\const bar = <0>;
+    );
+}
+
+test "references - local scope" {
+    try testReferences(
+        \\fn foo(<0>: u32, bar: u32) void {
+        \\    return <0> + bar;
+        \\}
+    );
+    if (skip_references_tests) return error.SkipZigTest;
+    try testReferences(
+        \\const foo = blk: {
+        \\    _ = blk: {
+        \\        const <0> = 0;
+        \\        break :blk <0>;
+        \\    };
+        \\    const <1> = 0;
+        \\    break :blk <1>;
+        \\};
+        \\const bar = foo;
+    );
+}
+
+test "references - label" {
+    if (skip_references_tests) return error.SkipZigTest;
+    try testReferences(
+        \\const foo = <0>: {
+        \\    break :<0> 0;
+        \\};
+    );
+}
+
+fn testReferences(source: []const u8) !void {
+    const file_uri = "file:///test.zig";
+    const new_name = "placeholder";
+
+    var phr = try helper.collectReplacePlaceholders(allocator, source, new_name);
+    defer phr.deinit(allocator);
+
+    var ctx = try Context.init();
+    defer ctx.deinit();
+
+    try ctx.requestDidOpen(file_uri, phr.new_source);
+
+    var i: usize = 0;
+    while (i < phr.locations.len) : (i += 1) {
+        const var_loc = phr.locations.items(.old)[i];
+        const var_name = offsets.locToSlice(source, var_loc);
+        const var_loc_middle = var_loc.start + (var_loc.end - var_loc.start) / 2;
+
+        const request = requests.References{
+            .params = .{
+                .textDocument = .{ .uri = file_uri },
+                .position = offsets.indexToPosition(source, var_loc_middle, ctx.server.offset_encoding),
+                .context = .{ .includeDeclaration = true },
+            },
+        };
+
+        const response = try ctx.requestGetResponse(?[]types.Location, "textDocument/references", request);
+        defer response.deinit();
+
+        const locations: []types.Location = response.result orelse {
+            std.debug.print("Server returned `null` as the result\n", .{});
+            return error.InvalidResponse;
+        };
+
+        for (locations) |response_location| {
+            const actual_name = offsets.rangeToSlice(phr.new_source, response_location.range, ctx.server.offset_encoding);
+            try std.testing.expectEqualStrings(file_uri, response_location.uri);
+            try std.testing.expectEqualStrings(new_name, actual_name);
+        }
+
+        // collect all new placeholder locations with the given name
+        const expected_locs: []offsets.Loc = blk: {
+            var locs = std.ArrayListUnmanaged(offsets.Loc){};
+            errdefer locs.deinit(allocator);
+
+            var j: usize = 0;
+            while (j < phr.locations.len) : (j += 1) {
+                const old_loc = phr.locations.items(.old)[j];
+                const new_loc = phr.locations.items(.new)[j];
+
+                const old_loc_name = offsets.locToSlice(source, old_loc);
+                if (!std.mem.eql(u8, var_name, old_loc_name)) continue;
+                try locs.append(allocator, new_loc);
+            }
+
+            break :blk locs.toOwnedSlice(allocator);
+        };
+        defer allocator.free(expected_locs);
+
+        var error_builder = ErrorBuilder.init(allocator, phr.new_source);
+        defer error_builder.deinit();
+        errdefer {
+            const note_loc = phr.locations.items(.new)[i];
+            error_builder.msgAtLoc("asked for references here", note_loc, .info, .{}) catch {};
+            error_builder.writeDebug();
+        }
+
+        // keeps track of expected locations that have been given by the server
+        // used to detect double references and missing references
+        var visited = try std.DynamicBitSetUnmanaged.initEmpty(allocator, expected_locs.len);
+        defer visited.deinit(allocator);
+
+        for (locations) |response_location| {
+            const actual_loc = offsets.rangeToLoc(phr.new_source, response_location.range, ctx.server.offset_encoding);
+
+            const index = found_index: {
+                for (expected_locs) |expected_loc, idx| {
+                    if (expected_loc.start != actual_loc.start) continue;
+                    if (expected_loc.end != actual_loc.end) continue;
+                    break :found_index idx;
+                }
+                try error_builder.msgAtLoc("server returned unexpected reference!", actual_loc, .err, .{});
+                return error.UnexpectedReference;
+            };
+
+            if (visited.isSet(index)) {
+                try error_builder.msgAtLoc("server returned duplicate reference!", actual_loc, .err, .{});
+                return error.DuplicateReference;
+            } else {
+                visited.set(index);
+            }
+        }
+
+        var has_unvisited = false;
+        var unvisited_it = visited.iterator(.{ .kind = .unset });
+        while (unvisited_it.next()) |index| {
+            try error_builder.msgAtLoc("expected reference here!", expected_locs[index], .err, .{});
+            has_unvisited = true;
+        }
+
+        if (has_unvisited) return error.ExpectedReference;
+    }
+}

tests/lsp_features/semantic_tokens.zig

@@ -1,7 +1,7 @@
 const std = @import("std");
 const zls = @import("zls");
 
-const Context = @import("context").Context;
+const Context = @import("../context.zig").Context;
 
 const requests = zls.requests;
 

tests/tests.zig

@@ -1,5 +1,7 @@
 comptime {
+    _ = @import("helper.zig");
     _ = @import("sessions.zig");
+
     _ = @import("utility/offsets.zig");
     _ = @import("utility/position_context.zig");
     _ = @import("utility/uri.zig");
@@ -11,6 +13,7 @@ comptime {
     // LSP features
     _ = @import("lsp_features/semantic_tokens.zig");
     _ = @import("lsp_features/inlay_hints.zig");
+    _ = @import("lsp_features/references.zig");
 
     // Language features
     _ = @import("language_features/cimport.zig");