Tag: tsconfig.json

If I have generated only typescript type declaration files from a project that am I importing, how can I make the types work?

If I have generated only typescript type declaration files from a project that am I importing, how can I make the types work? The types do not seem to include any mention of the package name so I assume some form of mapping would be required.

You’re correct that simply importing declaration files (.d.ts files) wouldn’t automatically work with your project unless they are properly configured. Here’s what you need to do to make the types work:

1. Mapping with tsconfig.json:

  • Locate your tsconfig.json file: This is the configuration file for your TypeScript compiler.
  • Add the compilerOptions property: Under this property, add "baseUrl" and "paths" options.
  • Set baseUrl: This option specifies the base directory where the compiler should start resolving modules. Set it to the directory containing the imported type declaration files.
  • Set paths: This option maps module names to their corresponding file paths. Define a mapping for the package you’re importing. Here’s the syntax:
JSON
"paths": {
  "your-package-name/*": ["path/to/your-package-name/*.d.ts"]
}
Replace "your-package-name" with the actual package name and "path/to/your-package-name/*.d.ts" with the path to the directory containing your type declaration files.

2. Using Type Aliases (Optional):

Even with the mapping, the imported types might not have the same names as in the original package. To address this:

  • Define type aliases in your own code for the imported types. This allows you to use familiar names for the types while still benefiting from type safety.

Example:

Assuming you’re importing a package named my-package:

tsconfig.json:

JSON
{
  "compilerOptions": {
    "baseUrl": "src/types", // Assuming your types are in a "types" folder
    "paths": {
      "my-package/*": ["../node_modules/my-package/*.d.ts"]
    }
  }
}

Your code:

TypeScript
// Assuming the type declaration defines an interface called "MyComponent"
import type { MyComponent } from "my-package";

// Define type alias
type MyCustomComponent = MyComponent;

// Use the alias like any other type
const myComponent: MyCustomComponent = { /* ... */ };
By following these steps, the TypeScript compiler should be able to properly resolve the type references and provide type safety based on the imported declaration files, even when the package name isn’t explicitly mentioned within them.

Should I include code I want typed but not published in tsconfig.json ?

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Should I include code in my tsconfig.json file in “includes” if I want it to be typed, but it is not code for the actual delivered product? For example, if it is build code that I want to be typed.

Whether to include build code in the “includes” list of your tsconfig.json file depends on a few factors:

1. Type Checking and Build Process:

  • If you want type checking and language features for build code during development, include it.
  • If the code is executed as part of the build process (e.g., custom webpack plugins), include it for accurate type checking during build.

2. Performance and Build Size:

  • If type checking build code is unnecessary or impacts performance negatively, exclude it.
  • If including a large amount of build code unnecessarily increases the built JavaScript output, exclude it.

3. Organization and Clarity:

  • If inclusion makes project structure clearer and tooling easier to set up, include it.
  • If exclusion better organizes code for separation of concerns, exclude it.

Best Practices:

  • Separate build code into a dedicated directory for organization and clarity.
  • Use a separate tsconfig.json file specifically for build code, ensuring appropriate configurations without affecting main code.
  • Consider “files” property for explicit file lists instead of “include” for fine-grained control and clarity.

Example tsconfig.json for build code:

JSON
{
  "compilerOptions": {
    // Options tailored for build code
  },
  "include": ["build/**/*.ts"]
}

Recommendations:

  • If build code benefits from type checking or is part of the build process, include it.
  • If performance, build size, or code separation are primary concerns, exclude it.
  • Prioritize clarity, organization, and tooling convenience for effective development.

I want the build code to be included in type checking in VSCode. Would any parent tsconfig.json be detected? Must it be called tsconfig.json?

Here’s how parent tsconfig.json files and type checking in VS Code work:

1. Inheritance:

  • VS Code automatically detects and uses parent tsconfig.json files within the same workspace folder.
  • It merges configurations from parent files, allowing for shared settings and overrides in child files.

2. File Searching:

  • VS Code searches for tsconfig.json files in the following order:
    1. Current workspace folder
    2. Parent workspace folders (recursively)
    3. User-specified path (using the “typescript.tsconfig.autoDetect” setting)

3. File Name:

  • Yes, the file must be named tsconfig.json. VS Code specifically looks for this file name.

Recommendations for VS Code:

  • Position tsconfig.json files strategically: Place them in relevant workspace folders for desired inheritance and configuration sharing.
  • Consider separate files for build code: Isolate build-related configurations for better organization and tailored type checking.
  • Manually specify a parent tsconfig.json: If necessary, use the “typescript.tsconfig.autoDetect” setting to direct VS Code to a specific parent file.

Additional Tips:

  • Use the “extends” property: Explicitly reference a parent tsconfig.json for clarity and maintainability, even within the same workspace folder.
  • Customize workspace settings: Adjust VS Code’s TypeScript settings for specific needs in your project (e.g., enabling or disabling automatic detection).

Example:

  • If you have a top-level tsconfig.json for shared settings and a separate tsconfig.build.json for build code within a nested ‘build’ folder, inheritance and automatic detection will typically work as expected in VS Code.