How I learn a library by reading code

Sandro Maglione

Sandro Maglione

Web development

Best way to learn a library? Study how experts are using it ๐Ÿ’๐Ÿผโ€โ™‚๏ธ

This week I explored effect-openai, an Effect wrapper of the OpenAI API, developed by the core team of Effect ๐Ÿ”ฅ

This is how I learn from someone else's code ๐Ÿฅท

When reading is better than writing

When you are new to a library you don't know the full extent of its API. You don't know how to use it in practice ๐Ÿค”

As you discover more methods, you start using them over and over again.

This creates a tendency to explore less, since the few methods you know may be enough for your usecase.

Solution: read how someone else is using the same library (even better if the code is from the core maintainers of the library itself ๐Ÿ’๐Ÿผโ€โ™‚๏ธ)

Effect OpenAI

This is what I did:

  1. Clone repository locally
  2. Install environment and dependencies
  3. Start reading the code from the entry file (bin.ts)

Every project generally has an entry file: start exploring the code from it before opening all the imported filesEvery project generally has an entry file: start exploring the code from it before opening all the imported files

Every file imports other files: I use VSCode to open and read each imported file ๐Ÿ’๐Ÿผโ€โ™‚๏ธ

import * as DevTools from "@effect/experimental/DevTools"
import * as NodeContext from "@effect/platform-node/NodeContext"
import * as NodeRuntime from "@effect/platform-node/NodeRuntime"
import * as Config from "effect/Config"
import * as ConfigProvider from "effect/ConfigProvider"
import * as Effect from "effect/Effect"
import * as Layer from "effect/Layer"
import * as Cli from "./Cli.js"
import * as OpenAI from "./OpenAI.js"

Look for patterns

Naturally you should recognize some methods, while others will be completely new.

Instead of looking at specific functions, try to recognize patterns and best practices.

/// Pattern 1: Errors โ›”๏ธ
export class OpenAIError extends Data.TaggedError("OpenAIError")<{
  readonly error: unknown
}> {}
/// Pattern 2: Options/Configuration ๐Ÿ› ๏ธ
export interface OpenAIOptions {
  readonly apiKey: Secret.Secret
  readonly organization: Option.Option<Secret.Secret>
/// Pattern 3: Implementation ๐Ÿ’ป
const make = (options: OpenAIOptions) =>
  Effect.gen(function*(_) {
    /// ...
/// Pattern 4: Dependency injection ๐Ÿ’‰
export class OpenAI extends Context.Tag("@services/OpenAI")<
  Effect.Effect.Success<ReturnType<typeof make>>
>() {
  static readonly Live = (config: Config.Config.Wrap<OpenAIOptions>) => /// ...

This is where you refine your previous knowledge and learn new methods.

Extra points if at the same time you share what you learn (this is what I do on X) ๐Ÿค

Reimplement a similar usecase

Knowledge is not enough. We need practice ๐Ÿ› ๏ธ

Take new methods and patterns and reimplement and example project to test your understanding

This time I created an API client using the same pattern as above ๐Ÿ‘‡

/// Pattern 1: Errors โ›”๏ธ
class ClientError extends Data.TaggedError("ClientError")<{
  error: Http.error.HttpClientError;
}> {}
/// Pattern 2: Options/Configuration ๐Ÿ› ๏ธ
export interface ClientOptions {
  baseUrl: string;
/// Pattern 3: Implementation ๐Ÿ’ป
const make = (options: ClientOptions) => /// ...
/// Pattern 4: Dependency injection ๐Ÿ’‰
export class Client extends Context.Tag("Client")<
  ReturnType<typeof make>
>() {
  static readonly Live = (config: Config.Config.Wrap<ClientOptions>) => /// ...

Bonus tips

Tip 1: Ask for help

Open an issue or contact directly the author of the repository. Most often than not people are more than willing to help and share ideas ๐Ÿ‘Œ

Tip 2: Read tests

When a method is unclear, the best way to focus specifically on how it works are tests. By definition a test aims to be the smallest example to verify a function. This makes it ideal for learning ๐Ÿ’ก

Tip 3: Ignore

Not everything is relevant to you, no need to read all the code. Focus more on what you can use in your projects.

Every once in a while it's good to write less and read more.

Nonetheless, the best way to learn programming is practice: after reading go ahead and start building ๐Ÿš€

Some updates planned for the blog (what about step by step tutorial series?) and new open source updates (what about Effect in dart?). Stay tuned ๐Ÿ›œ

See you next ๐Ÿ‘‹

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