Tool: Flow for static type checking/ static analysis

[Q2L2]

Explored a tool for type checking / static analysis
Tool integration can be found in flow/ and logs and monitor logs will go to /tmp/flow/zSworkspaceszSnodebb-spring-26-98k.log, /tmp/flow/zSworkspaceszSnodebb-spring-26-98k.monitor_log r(espectively)
Output for running the test:

Pros:

• Catches type errors before runtime
• Helpful for reduceing common bugs like undefined values
• Detects errors such as null/undefined access, invalid function calls, array out-of-bounds, and object property typos quickly

Cons:

• Difficult setup and installation process since prebuilt binaries can fail on older systems

[Q2L2]

What is Flow?

• Flow is a static type checker tool that performs automated analysis on the code through static type annotations to help developers catch type-related errors (including type mismatches, null pointer exceptions, and incorrect function arguments).
• Documentation: https://flow.org/en/docs/

How to customize Flow?

• Users can configure .flowconfig file to manage the strictness, module resolution and library definition, customizing aspects like strict typing, ignoring folders and mapping modules.

How can/should Flow be integrated into a development process?
Set up:

1. First install @babel/core, @babel/cli, @babel/preset-flow, and babel-plugin-syntax-hermes-parser with either Yarn or npm.
2. Create a .babelrc file at the project root with the @babel/preset-flow preset and babel-plugin-syntax-hermes-parser plugin.
3. Can compile source files into another directory by running: ./node_modules/.bin/babel src/ -d lib/
4. Adding “build” and “prepublishOnly” scripts in package.json: "scripts": { "build": "babel src/ -d lib/", "prepublishOnly": “npm run build" } }

Installing Flow into the local project:

1. Run: npm install --save-dev flow-bin
2. Add a “flow” script into package.json: "scripts": { "flow": "flow" }.
3. Run: npm run flow init to create a .flowconfig file in the project root
4. Run Flow: npm run flow

What are limitations of Flow?
Some limitations of the tool include false positives and flagging issues that developers don’t care about. Sometimes Flow can flag safe code when it infers an overly strict type or cannot follow flow of data through complex logic.