- to build the app:
docker build -t repository-search .
- to start the app
docker run -e REACT_APP_GITHUB_TOKEN=yourGithubToken repository-search
The project aim is to showcase DDD (Domain-Driven Design) principles within a React application.
The project is structured into three main domains:
- Repository Search UI (Core): The central domain focused on presenting repositories to users.
- API: Handles all GraphQL communication, encapsulating the business logic for data exchange.
- Error Handling: Comprises two subdomains dedicated to managing errors - one for API errors and another for UI errors.
This is the core domain responsible for the primary functionality of displaying repositories to users. It operates independently, using a specific adapter to communicate with the API. The adapter is divided into a fetch function for direct API interaction and a transform function that converts API responses to UI-friendly data.
This domain includes all the logic related to GraphQL communication, abstracting the complexities of data exchange from other domains.
This domain is designed to manage errors, consisting of two subdomains:
- API Error Module: Manages errors related to API communication.
- UI Error Module: Handles errors presented to the user.
API errors are handled by wrapping asynchronous functions with withErrorLog, which logs errors without changing the function's original behavior.
export const client = new ApolloClient({
uri: apolloClientUri,
cache: new InMemoryCache(),
headers: {
Authorization: `Bearer ${process.env[`REACT_APP_GITHUB_TOKEN`]}`,
},
});
client.query = withErrorLog(client.query);UI error handling requires wrapping the application with an Error Module Provider to effectively manage UI errors.
<ErrorHandlingProvider>{children}</ErrorHandlingProvider>useWithErrorHandling is used similarly to handleErrors, managing side effects like displaying errors to the user.
const props = useWithErrorHandling(
usePaginatedResource<Repository>(gqlGithubConnectorData),
);The project includes behavioral tests for component interactions and unit tests for individual functions, ensuring both the overall application behavior and the utility functions meet the requirements. To test components interactions in bounded contexts integration tests have been added
To minimize hardcoded types, type transformations are used extensively, with tests ensuring their accuracy and reliability.
Example:
// src/utils/test/transformations.type-test.ts
type SimpleNestedObject = {
primaryField: number;
nestedObject: {
nestedField: string;
anotherNestedField: boolean;
};
};
assertType<ConvertFieldsToSnakeCase<SimpleNestedObject>>({
primary_field: 1,
nested_object: {
nested_field: `value`,
another_nested_field: true,
},
});Test maintainability is enhanced through dynamic test naming
describe(`${RepositoriesContainer.name} component`, () => {
it(`calls ${useWithErrorHandling.name} on error`, () => {
/.../
})
})reusable test functions
export const expectRepositoriesToBePresent = (repos: Repository[]): void => {
repos
.flatMap((repo) => [repo.name, getStargazers(repo), getForks(repo)])
.forEach((item: string) => {
expect(screen.getByText(item, { exact: false })).toBeInTheDocument();
});
};and meta-programming techniques for focused testing.
Example: An object that allows for destructuring at any level without throwing an error.
const handler: ProxyHandler<Record<string, unknown>> = {
get: (target, prop) =>
prop in target
? target[prop as keyof typeof target]
: new Proxy({}, handler),
};
export const anything = new Proxy<Record<string, unknown>>({}, handler) as any;To preserve the type:
export const getMocked<T extends Record<string, unknown>> = () => new Proxy<Record<string, unknown>>({}, handler) as T;
The application utilizes a variety of models:
- entities - primary objects of the domain
- value objects - represent descriptive aspects of the domain
- services - process domain-specific business rules
- repositories - data retrieved from the storage
- aggregations - a cluster of domain objects that can be treated as a single unit
React hooks are used as factories to spawn objects representing asynchronous resources, streamlining data management within the application.
Three factories are implemented: one for configuring pagination mechanisms, another for creating resources with asynchronous data, and a third dedicated to constructing paginated asynchronous resources. Functionality and scalability are achieved through the inversion of the control paradigm.
AsynchResource requires an API adapter as a dependency, whereas a PaginatedResource requires a CursorBasedPagination object describing how the pagination works and AsynchResource, which will be controlled with the pagination. Thanks to this, any kind of pagination mechanism could be used with any kind of asynchronous resource as long as interfaces match.
The project ensures a clear separation of concerns, with pure data transformations and decoupled application components.
In /utils folder pure functions (not associated with any domain) are stored, used later in the application
In order to make type system scalable - there are as few hard-coded types as possible and all other types are derived.
There are 4 main components in the app
The MUI library and styled components are used for styling, providing a cohesive and customizable UI. A theme object is used to manage variables:
const theme = createTheme({
spacing: 8,
});
export const themeVariables = {
spacingBig: `${theme.spacing(2.5)}`,
background: `#faf9fd`,
};- husky - to run tests on each commit
- craco - to handle path aliases
- prettier - code formatting
- jslint - code linting
In order not to use API token directly in the frontend code, a token is stored as an env variable. It can be provided in .env.local file
In the project directory, you can run:
Runs the app in the development mode.
Open http://localhost:3000 to view it in the browser.
The page will reload if you make edits.
You will also see any lint errors in the console.
Launches the test runner in the interactive watch mode.
See the section about running tests for more information.
Builds the app for production to the build folder.
It correctly bundles React in production mode and optimizes the build for the best performance.
The build is minified and the filenames include the hashes.
Your app is ready to be deployed!
See the section about deployment for more information.
Note: this is a one-way operation. Once you eject, you can’t go back!
If you aren’t satisfied with the build tool and configuration choices, you can eject at any time. This command will remove the single build dependency from your project.
Instead, it will copy all the configuration files and the transitive dependencies (webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except eject will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own.
You don’t have to ever use eject. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it.