optionals

src/lsp/types.zig

@@ -108,7 +108,8 @@ pub fn initializeResultJson(allocator: std.mem.Allocator) ![]const u8 {
             "\"semanticTokensProvider\":{{\"legend\":{{" ++
             "\"tokenTypes\":[\"namespace\",\"type\",\"enum\",\"struct\",\"parameter\",\"variable\",\"enumMember\",\"function\",\"keyword\",\"number\",\"string\",\"operator\"]," ++
             "\"tokenModifiers\":[\"declaration\",\"readonly\"]" ++
-            "}},\"full\":true}}}}}}",
+            "}},\"full\":true}}," ++
+            "\"inlayHintProvider\":true}}}}",
         .{},
     );
 }
@@ -358,3 +359,29 @@ pub fn publishDiagnosticsJson(allocator: std.mem.Allocator, uri: []const u8, dia
     try buf.appendSlice(allocator, "]}");
     return buf.items;
 }
+
+pub const InlayHint = struct {
+    line: u32,
+    character: u32,
+    label: []const u8,
+    kind: u32 = 1, // 1 = Type
+    padding_left: bool = true,
+    padding_right: bool = false,
+};
+
+/// Build inlay hints JSON array response.
+pub fn inlayHintsJson(allocator: std.mem.Allocator, hints: []const InlayHint) ![]const u8 {
+    var buf = std.ArrayList(u8).empty;
+    try buf.append(allocator, '[');
+    for (hints, 0..) |hint, idx| {
+        if (idx > 0) try buf.append(allocator, ',');
+        const label_escaped = try jsonString(allocator, hint.label);
+        const json = try std.fmt.allocPrint(allocator,
+            "{{\"position\":{{\"line\":{d},\"character\":{d}}},\"label\":{s},\"kind\":{d},\"paddingLeft\":{s},\"paddingRight\":{s}}}",
+            .{ hint.line, hint.character, label_escaped, hint.kind, if (hint.padding_left) "true" else "false", if (hint.padding_right) "true" else "false" },
+        );
+        try buf.appendSlice(allocator, json);
+    }
+    try buf.append(allocator, ']');
+    return buf.items;
+}