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Improve Emitter/Library authoring documentation #2725

Merged
merged 13 commits into from
Dec 14, 2023
1 change: 1 addition & 0 deletions cspell.yaml
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ words:
- jsyaml
- keyer
- lzutf
- mocharc
- msbuild
- MSRC
- multis
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163 changes: 104 additions & 59 deletions docs/extending-typespec/basics.md
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Expand Up @@ -23,9 +23,9 @@ The following is a high level overview of the contents of a TypeSpec package. Th
- **src/lib.ts** - the TypeSpec library definition file
- **package.json** - metadata about your TypeSpec package

## Initial setup
## 1 - Initial setup

### 1. Initialize your package directory & package.json
### a. Initialize your package directory & package.json

Run the following commands:

Expand All @@ -37,34 +37,34 @@ Run the following commands:

After filling out the wizard, you will have a package.json file that defines your typespec library.

Unlike node libraries which support CommonJS (cjs), TypeSpec libraries must be Ecmascript Modules. So open your `package.json` and add the following top-level configuration key:
Unlike node libraries which support CommonJS (cjs), TypeSpec libraries must be Ecmascript Modules. Open your `package.json` and add the following top-level configuration key:

```json
```jsonc
"type": "module"
```

### 2. Install TypeSpec dependencies
### b. Install TypeSpec dependencies

Run the following command:

```bash
npm install --save-peer @typespec/compiler
```

You may have need of other dependencies in the TypeSpec standard library depending on what you are doing. E.g. if you want to use the metadata found in `@typespec/openapi` you will need to install that as well.
You may have need of other dependencies in the TypeSpec standard library depending on what you are doing (e.g. if you want to use the metadata found in `@typespec/openapi` you will need to install that as well).

See [dependency section](#defining-dependencies) for information on how to define your dependencies.

### 2. Define your main files
### c. Define your main files

Your package.json needs to refer to two main files: your node module main file, and your TypeSpec main. The node module main file is the `"main"` key in your package.json file, and defines the entrypoint for your library when consumed as a node library, and must reference a js file. The TypeSpec main defines the entrypoint for your library when consumed from a TypeSpec program, and may reference either a js file (when your library doesn't contain any typespec types) or a TypeSpec file.

```json
"main": "dist/index.js",
```jsonc
"main": "dist/src/index.js",
"tspMain": "lib/main.tsp"
```

### 3. Install and initialize TypeScript
### d. Install and initialize TypeScript

Run the following commands:

Expand All @@ -75,15 +75,16 @@ npx tsc --init --strict

This will create `tsconfig.json`. But we need to make a couple changes to this. Open `tsconfig.json` and set the following settings:

```json
"module": "Node16", // This and next setting tells TypeScript to use the new ESM import system to resolve types.
"moduleResolution": "Node16",
"target": "es2019",
"rootDir": "./src",
"outDir": "./dist",
```jsonc
"module": "Node16", // This and next setting tells TypeScript to use the new ESM import system to resolve types.
"moduleResolution": "Node16",
"target": "es2019",
"rootDir": ".",
"outDir": "./dist",
"sourceMap": true,
```

### 4. Create `lib.ts`
### e. Create `lib.ts`

Open `./src/lib.ts` and create your library definition that registers your library with the TypeSpec compiler and defines any diagnostics your library will emit. Make sure to export the library definition as `$lib`.

Expand All @@ -107,7 +108,7 @@ export const { reportDiagnostic, createDiagnostic, createStateSymbol } = $lib;

Diagnostics are used for linters and decorators which are covered in subsequent topics.

### 5. Create `index.ts`
### f. Create `index.ts`

Open `./src/index.ts` and import your library definition:

Expand All @@ -116,19 +117,32 @@ Open `./src/index.ts` and import your library definition:
export { $lib } from "./lib.js";
```

### 6. Build TypeScript
### g. Build TypeScript

TypeSpec can only import JavaScript files, so any time changes are made to TypeScript sources, they need to be compiled before they are visible to TypeSpec. To do so, run `npx tsc -p .` in your library's root directory. You can also run `npx tsc -p --watch` if you would like to re-run the TypeScript compiler whenever files are changed.
TypeSpec can only import JavaScript files, so any time changes are made to TypeScript sources, they need to be compiled before they are visible to TypeSpec. To do so, run `npx tsc -p .` in your library's root directory. You can also run `npx tsc -p . --watch` if you would like to re-run the TypeScript compiler whenever files are changed.

### 7. Add your main TypeSpec file
Alternatively, you can add these as scripts in your `package.json` to make them easier to invoke. Consider adding the following:

```jsonc
"scripts": {
"clean": "rimraf ./dist ./temp",
"build": "tsc -p .",
"watch": "tsc -p . --watch",
"test": "mocha"
}
```

You can then run `npm run build` or `npm run watch` to build or watch your library.

### h. Add your main TypeSpec file

Open `./lib/main.tsp` and import your JS entrypoint. This ensures that when typespec imports your library, the code to define the library is run. In later topics when we add decorators, this import will ensure those get exposed as well.

```typespec
import "../dist/index.js";
```

## Adding TypeSpec types to your library
## 2. Adding TypeSpec types to your library

Open `./lib/main.tsp` and add any types you want to be available when users import this library. It is also strongly recommended you put these types in a namespace that corresponds with the library name. For example, your `./lib/main.tsp` file might look like:

Expand All @@ -142,7 +156,7 @@ model Person {
}
```

## Defining Dependencies
## 3. Defining Dependencies

Defining dependencies in a TypeSpec library should be following these rules:

Expand Down Expand Up @@ -174,44 +188,42 @@ TypeSpec libraries are defined using `peerDependencies` so we don't end-up with
}
```

## Publishing your TypeSpec library
## 4. Testing your TypeSpec library

To publish to the public npm registry, follow [their documentation](https://docs.npmjs.com/creating-and-publishing-unscoped-public-packages).
TypeSpec provides a testing framework to help testing libraries. Examples here are shown using `mocha` but any other JS test framework can be used.

## Importing your TypeSpec library
### a. Add devDependencies

Once your TypeSpec library is published, your users can install and use it just like any of the TypeSpec standard libraries. First, they have to install it:
Verify that you have the following in your `package.json`:

```bash
npm install $packageName
```

Next, they import it into their TypeSpec program and use the namespace (if desired):

```typespec
import "MyLibrary";
using MyLibrary;

model Employee extends Person {
job: string;
"devDependencies": {
"@types/node": "~18.11.9",
"@types/mocha": "~10.0.1",
"mocha": "~10.2.0",
"source-map-support": "^0.5.21"
}
```

## Next steps

TypeSpec libraries can contain more than just types. Read the subsequent topics for more details on how to write [decorators](./create-decorators.md), [emitters](./emitters-basics.md) and [linters](./linters.md).
Also add a `.mocharc.yaml` file at the root of your project.

## Testing

TypeSpec provides a testing framework to help testing libraries. Examples here are shown using `mocha` but any other JS test framework can be used.
```yaml
timeout: 5000
require: source-map-support/register
spec: "dist/test/**/*.test.js"
```

### Define the testing library
### b. Define the testing library

First step is to define how your library can be loaded from the test framework. This will let your library to be reused by other library test.
The first step is to define how your library can be loaded from the test framework. This will let your library to be reused by other library test.

1. Create a new file `./src/testing/index.ts` with the following content

```ts
import { resolvePath } from "@typespec/compiler";
import { createTestLibrary } from "@typespec/compiler/testing";
import { fileURLToPath } from "url";

export const MyTestLibrary = createTestLibrary({
name: "<name-of-npm-pkg>",
// Set this to the absolute path to the root of the package. (e.g. in this case this file would be compiled to ./dist/src/testing/index.js)
Expand All @@ -221,7 +233,7 @@ export const MyTestLibrary = createTestLibrary({

2. Add an `exports` for the `testing` endpoint to `package.json` (update with correct paths)

```json
```jsonc
{
// ...
"main": "dist/src/index.js",
Expand All @@ -238,11 +250,11 @@ export const MyTestLibrary = createTestLibrary({
}
```

### Define the test host and test runner for your library
### c. Define the test host and test runner for your library

Define some of the test framework base pieces that will be used in the tests. There is 2 functions:
Define some of the test framework base pieces that will be used in the tests. There are 2 functions:

- `createTestHost`: This is a lower level api that provide a virtual file system.
- `createTestHost`: This is a lower level API that provides a virtual file system.
- `createTestRunner`: This is a wrapper on top of the test host that will automatically add a `main.tsp` file and automatically import libraries.

Create a new file `test/test-host.js` (change `test` to be your test folder)
Expand All @@ -258,14 +270,14 @@ export async function createMyTestHost() {
});
}
export async function createMyTestRunner() {
const host = await createOpenAPITestHost();
const host = await createMyTestHost();
return createTestWrapper(host, { autoUsings: ["My"] });
}
```

### Write tests
### d. Write tests

After setting up that infrastructure you can start writing tests.
After setting up that infrastructure you can start writing tests. For tests to be recognized by mocha the file names must follow the following format: `<name>.test.ts`

```ts
import { createMyTestRunner } from "./test-host.js";
Expand All @@ -278,30 +290,30 @@ describe("my library", () => {
});

// Check everything works fine
it("does this", () => {
const { Foo } = runner.compile(`
it("does this", async () => {
const { Foo } = await runner.compile(`
@test model Foo {}
`);
strictEqual(Foo.kind, "Model");
});

// Check diagnostics are emitted
it("errors", () => {
const diagnostics = runner.diagnose(`
it("errors", async () => {
const diagnostics = await runner.diagnose(`
model Bar {}
`);
expectDiagnostics(diagnostics, { code: "...", message: "..." });
});
});
```

#### `@test` decorator
#### e. `@test` decorator

The `@test` decorator is a decorator loaded in the test environment. It can be used to collect any decorable type.
When using the `compile` method it will return a `Record<string, Type>` which is a map of all the types annoted with the `@test` decorator.

```ts
const { Foo, CustomName } = runner.compile(`
const { Foo, CustomName } = await runner.compile(`
@test model Foo {}

model Bar {
Expand All @@ -312,3 +324,36 @@ const { Foo, CustomName } = runner.compile(`
Foo; // type of: model Foo {}
CustomName; // type of : Bar.name
```

#### f. Install the mocha test explorer for VSCode (optional)

If you are using VSCode, you can install the [mocha test explorer](https://marketplace.visualstudio.com/items?itemName=hbenl.vscode-mocha-test-adapter) to run your tests from the editor. This will also allow you easily debug into your tests.

You should now be able to discover, run and debug into your tests from the test explorer.

## 5. Publishing your TypeSpec library

To publish to the public npm registry, follow [their documentation](https://docs.npmjs.com/creating-and-publishing-unscoped-public-packages).

## 6. Importing your TypeSpec library

Once your TypeSpec library is published, your users can install and use it just like any of the TypeSpec standard libraries. First, they have to install it:

```bash
npm install $packageName
```

Next, they import it into their TypeSpec program and use the namespace (if desired):

```typespec
import "MyLibrary";
using MyLibrary;

model Employee extends Person {
job: string;
}
```

## 7. Next steps

TypeSpec libraries can contain more than just types. Read the subsequent topics for more details on how to write [decorators](./create-decorators.md), [emitters](./emitters-basics.md) and [linters](./linters.md).
6 changes: 3 additions & 3 deletions docs/extending-typespec/emitter-framework.md
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Expand Up @@ -24,11 +24,11 @@ Let's walk through each of these types in turn.

The asset emitter is responsible for driving the emit process. It has methods for taking TypeSpec types to emit, and maintains the state of your current emit process including the declarations you've accumulated, current emit context, and converting your emitted content into files on disk.

To create your asset emitter, call `createAssetEmitter` on your emit context in `$onEmit`. It takes the TypeEmitter which is covered in the next section. Once created, you can call `emitProgram()` to emit every type in the TypeSpec graph. Otherwise, you can call `emitType(someType)` to emit specific types instead.
To create your asset emitter, call `getAssetEmitter` on your emit context in `$onEmit`. It takes the TypeEmitter which is covered in the next section. Once created, you can call `emitProgram()` to emit every type in the TypeSpec graph. Otherwise, you can call `emitType(someType)` to emit specific types instead.

```typescript
export async function $onEmit(context: EmitContext) {
const assetEmitter = context.createAssetEmitter(MyTypeEmitter);
const assetEmitter = context.getAssetEmitter(MyTypeEmitter);

// emit my entire typespec program
assetEmitter.emitProgram();
Expand Down Expand Up @@ -59,7 +59,7 @@ class MyCodeEmitter extends CodeTypeEmitter {
}
```

Passing this to `createAssetEmitter` and calling `assetEmitter.emitProgram()` will console.log all the models in the program.
Passing this to `getAssetEmitter` and calling `assetEmitter.emitProgram()` will console.log all the models in the program.

#### EmitterOutput

Expand Down
11 changes: 7 additions & 4 deletions docs/extending-typespec/emitters-basics.md
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Expand Up @@ -21,12 +21,15 @@ A TypeSpec emitter exports a function named `$onEmit` from its main entrypoint.
For example, the following will write a text file to the output directory:

```typescript
import { EmitContext } from "@typespec/compiler";
import Path from "path";
import { EmitContext, emitFile, resolvePath } from "@typespec/compiler";

export async function $onEmit(context: EmitContext) {
const outputDir = Path.join(context.emitterOutputDir, "hello.txt");
await context.program.host.writeFile(outputDir, "hello world!");
if (!context.program.compilerOptions.noEmit) {
await emitFile(context.program, {
path: resolvePath(context.emitterOutputDir, "hello.txt"),
content: "Hello world\n",
});
}
}
```

Expand Down
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