Add safe transcription errors and opt-in private debug logging

tests/config_test.cpp

@@ -28,16 +28,55 @@ int main(int argc, char** argv) {
     ::setenv("XDG_CONFIG_HOME", dir.c_str(), 1);
     assert(load_config(path).buttons.empty());
     assert(!load_config(path).experimental_input_priority);
+    assert(!load_config(path).advanced_debug);
     assert(load_config(path).wrist.width == .30f);
     auto example = load_config(std::filesystem::path(argv[1]) / "config.example.json");
     assert(example.buttons.at("ptt") == "/user/hand/right/input/x");
     assert(example.font.empty());
     assert(!example.experimental_input_priority);
+    assert(!example.advanced_debug);
     assert(example.wrist.y == .18f && example.wrist.z == .089f);
     std::filesystem::create_directories(path.parent_path());
-    put(path, R"({"input_priority":"experimental"})");
+    assert(save_advanced_debug(path, true));
+    assert(load_config(path).advanced_debug);
+    assert(get(path).find("\"advanced_debug\":true") != std::string::npos);
+    assert(save_advanced_debug(path, false));
+    assert(!load_config(path).advanced_debug);
+    for (const auto* invalid : {R"({"advanced_debug":"true"})", R"({"advanced_debug":0})",
+                               R"({"advanced_debug":null})", R"({"advanced_debug":[]})"}) {
+        put(path, invalid);
+        fails([&] { load_config(path); });
+        assert(!save_advanced_debug(path, true));
+        assert(get(path) == invalid);
+    }
+    put(path, R"({"font":"escaped \u0061 and \"quotes\"","input_priority":"experimental","wrist":{"y":0.21},"theme":{"ink":"#123ABC"},"buttons":{"enter":""}})");
+    const auto customized = get(path);
+    assert(save_advanced_debug(path, true));
+    assert(load_config(path).advanced_debug);
+    assert(get(path).find(customized.substr(1, customized.size() - 2)) != std::string::npos);
+    assert(save_advanced_debug(path, false));
+    assert(!load_config(path).advanced_debug);
+    auto before = get(path);
+    assert(save_advanced_debug(path, false) && get(path) == before);
+    put(path, R"({"advanced_debug":false, "font":"kept"})");
+    assert(save_advanced_debug(path, true));
+    assert(get(path) == R"({"advanced_debug":true, "font":"kept"})");
+    before = get(path);
+    put(path, R"({"font":"bad","font":"duplicate"})");
+    assert(!save_advanced_debug(path, true));
+    assert(get(path) == R"({"font":"bad","font":"duplicate"})");
+    put(path, before);
+    auto link = dir / "linked-config";
+    std::filesystem::create_symlink(path, link);
+    assert(!save_advanced_debug(link, false));
+    assert(get(path) == before);
+    std::filesystem::remove(link);
+    put(path, R"({"font":")" + std::string(4090, 'x') + R"("})");
+    before = get(path);
+    assert(!save_advanced_debug(path, true) && get(path) == before);
+    put(path, R"({"input_priority":"experimental","advanced_debug":true})");
     auto experimental = load_config(path);
-    assert(experimental.experimental_input_priority);
+    assert(experimental.experimental_input_priority && experimental.advanced_debug);
     // A priority request must preserve the user's existing action manifest/bindings.
     assert(action_manifest(argv[1], experimental) == std::filesystem::absolute(std::filesystem::path(argv[1]) / "actions.json"));
     put(path, R"({"input_priority":"normal"})");