dets

(pronounced: deee - ts)

A TypeScript declaration file bundler.

dets is a small utility to generate single-file TypeScript declaration files. It can operate in multiple modes.

It is best used if you want to selectively export an API or if you want to build an isolated d.ts file that does not depend on any other declaration packages.

Installation

You can run dets directly via npx. Otherwise, if you want to use it globally you can install it via:

npm i dets -g

We recommend a local installation though:

npm i dets --save-dev

Usage

There are two primary ways of using dets: Either via the command line or programmatically.

Special Treatments

Ignoring Properties

By default, members that have a @ignore comment will be ignored. Therefore, an interface like

interface Foo {
  bar: boolean;
  /**
   * @ignore
   */
  foo: string;
}

will be changed by dets to look like:

interface Foo {
  bar: boolean;
}

This can be disabled via the CLI or programmatic options (--no-ignore). Additionally, a special comment like @dets_preserve could be added, too.

interface Foo {
  bar: boolean;
  /**
   * @ignore
   * @dets_preserve
   */
  foo: string;
}

Here, the property is kept, but the dets_preserve dets comment will be removed:

interface Foo {
  bar: boolean;
  /**
   * @ignore
   */
  foo: string;
}

Removing Properties

When doing interface merging certain properties may be desired to be hidden. To do this a special tag comment @dets_removeprop is used:

// original interface
interface Foo {
  foo: string;
  bar: boolean;
}

// somewhere later
/**
 * @dets_removeprop foo
 */
interface Foo {
  qxz: number;
}

This results in the merged interface, just without the excluded property:

interface Foo {
  bar: boolean;
  qxz: number;
}

Removing Inheritance Clauses

When doing interface merging certain extend clauses may be desired to be hidden. To do this a special tag comment @dets_removeclause is used:

// original interface
interface Foo extends FooBase1, FooBase2 {
  foo: string;
}

// somewhere later
/**
 * @dets_removeclause FooBase1
 */
interface Foo {}

This results in the merged interface, just without the excluded clauses:

interface Foo extends FooBase2 {
  foo: string;
}

From the CLI

An example call for dets from the command line is:

dets src/index.ts --name foo --files src/**/*.ts --out dist/index.d.ts

Here we use a glob pattern for the input files and an explicit path for the output.

The available command line arguments are:

Positionals:
  entry  The entry level modules to be consumed.          [string] [default: []]

Options:
  --help                Show help                                      [boolean]
  --version             Show version number                            [boolean]
  --name                Sets the name of the module.   [string] [default: "foo"]
  --files               Sets the files referenced by TypeScript.
                                                [array] [required] [default: []]
  --types               Sets the type entry modules to export via their file
                        path.                              [array] [default: []]
  --apis                Sets the interfaces to include using
                        "InterfaceName:FilePath" syntax.   [array] [default: []]
  --imports             Sets the imports to avoid bundling in via their package
                        names.                             [array] [default: []]
  --ignore              Actively uses the ignore comment to drop properties.
                                                       [boolean] [default: true]
  --module-declaration  Wraps the declaration in a "declare module" block.
                                                       [boolean] [default: true]
  --out                 Sets the path to the output file.
                                         [string] [default: "./dist/index.d.ts"]

If name is omitted then the name from the closest package.json is taken.

The files and types allow more fine-grained control what files are seen by TypeScript and what types should be exported. Usually, you'd want to use the positional entry level modules instead.

From Node Applications

An example code for using dets in a Node.js application is:

import { generateDeclaration } from "dets";
import { writeFileSync } from "fs";

const content = await generateDeclaration({
  name: "foo",
  root: process.cwd(),
  files: ["src/**/*.ts"],
  types: ["src/index.ts"]
});

writeFileSync("dist/index.d.ts", content, "utf8");

This is effectively the same call as the example in the CLI section.

There are multiple other possibilities, which may be relevant.

The basis for most operations is a DeclVisitorContext, which can be created via the setupVisitorContext function.

import { setupVisitorContext } from "dets";

const context = setupVisitorContext('foo', ["src/**/*.ts"]);

Using the DeclVisitorContext you can fill from an exported object, which is automatically enriched with all available information form the given input files:

import { fillVisitorContextFromApi } from "dets";

fillVisitorContextFromApi(context, 'src/types/api.ts', 'MyExportedApi');

Alternatively, just get all exports from a given module.

Using the DeclVisitorContext you can fill from an exported object, which is automatically enriched with all available information form the given input files:

import { fillVisitorContextFromTypes } from "dets";

fillVisitorContextFromTypes(context, 'src/types/index.ts');

Using Plugins

dets also comes with an integrated plugin system that allows customizing the behavior such as modifying the captured type information.

As an example:

import { generateDeclaration, createExcludePlugin } from "dets";
import { writeFileSync } from "fs";

const content = await generateDeclaration({
  name: "foo",
  root: process.cwd(),
  files: ["src/**/*.ts"],
  types: ["src/index.ts"],
  plugins: [createExcludePlugin(['foo'])],
});

writeFileSync("dist/index.d.ts", content, "utf8");

This excludes the foo module from the output. Since the foo module was the subject to create only the declaration mergings on existing modules survive.

Furthermore, custom plugins can be created, too:

import { generateDeclaration } from "dets";

const printFoundModulesInConsole = {
  // type of the plugin ('before-init' | 'before-process' | 'after-process' | 'before-stringify')
  type: 'after-process',
  // name of the plugin
  name: 'console-printer',
  // function to run with the created context
  run(context) {
    console.log('Found the following modules:', Object.keys(context.modules));
  },
};

await generateDeclaration({
  name: "foo",
  root: process.cwd(),
  files: ["src/**/*.ts"],
  types: ["src/index.ts"],
  plugins: [printFoundModulesInConsole],
});

The provided syntax is considered "classic" - you can also create "modern" plugins using the full lifecycle:

import { generateDeclaration } from "dets";

const printFoundModulesInConsole = {
  // name of the plugin
  name: 'console-printer',
  // function to run with the created context
  'before-init'(context) {
    context.log.info('Starting the console-printer plugin');
  },
  'after-process'(context) {
    console.log('Found the following modules:', Object.keys(context.modules));
  },
};

await generateDeclaration({
  name: "foo",
  root: process.cwd(),
  files: ["src/**/*.ts"],
  types: ["src/index.ts"],
  plugins: [printFoundModulesInConsole],
});

The advantage of the modern plugin approach is that you can easily modify / integrate into multiple phases of dets with just a single plugin.

Development

Right now dets is fully in development. So things may change in the (near) future.

Any ideas, issues, or enhancements are much appreciated!

We follow common sense here, so I hope that we do not need a long code of conduct or anything overall complex for everyone to feel welcome here.

License

MIT License (MIT). For more information see LICENSE file.