Testing and Typescript declaration merging

[francisdaigle]

🐛 Bug Report

• Plugin declarations not being merged as expected
• Possibly related to plugin load order

❯ npm test

> fastify@1.0.0 test
> npm run build:ts && tsc -p test/tsconfig.test.json && tap test/**/*.test.ts


> fastify@1.0.0 build:ts
> tsc

 PASS  test/plugins/support.test.ts 1 OK 24.624ms
 FAIL  test/routes/example.test.ts
 ✖ ⨯ Unable to compile TypeScript: src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist on type 'FastifyInstance<Server, IncomingMessage, ServerResponse, FastifyLoggerInstance>'.

  test: example is loaded
  stack: |
    createTSError (node_modules/ts-node/src/index.ts:434:12)
    reportTSError (node_modules/ts-node/src/index.ts:438:19)
    getOutput (node_modules/ts-node/src/index.ts:578:36)
    Object.compile (node_modules/ts-node/src/index.ts:775:32)
    Module.m._compile (node_modules/ts-node/src/index.ts:858:43)
    require.extensions.<computed> (node_modules/ts-node/src/index.ts:861:12)
    Object.<anonymous> (node_modules/append-transform/index.js:62:4)
  at:
    line: 434
    column: 12
    file: node_modules/ts-node/src/index.ts
    function: createTSError
  type: TSError
  diagnosticText: >
    src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist
    on type 'FastifyInstance<Server, IncomingMessage, ServerResponse,
    FastifyLoggerInstance>'.
  diagnosticCodes:
    - 2339
  tapCaught: returnedPromiseRejection

 FAIL  test/routes/root.test.ts
 ✖ ⨯ Unable to compile TypeScript: src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist on type 'FastifyInstance<Server, IncomingMessage, ServerResponse, FastifyLoggerInstance>'.

  test: default root route
  stack: |
    createTSError (node_modules/ts-node/src/index.ts:434:12)
    reportTSError (node_modules/ts-node/src/index.ts:438:19)
    getOutput (node_modules/ts-node/src/index.ts:578:36)
    Object.compile (node_modules/ts-node/src/index.ts:775:32)
    Module.m._compile (node_modules/ts-node/src/index.ts:858:43)
    require.extensions.<computed> (node_modules/ts-node/src/index.ts:861:12)
    Object.<anonymous> (node_modules/append-transform/index.js:62:4)
  at:
    line: 434
    column: 12
    file: node_modules/ts-node/src/index.ts
    function: createTSError
  type: TSError
  diagnosticText: >
    src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist
    on type 'FastifyInstance<Server, IncomingMessage, ServerResponse,
    FastifyLoggerInstance>'.
  diagnosticCodes:
    - 2339
  tapCaught: returnedPromiseRejection

 FAIL  test/routes/root.test.ts 1 failed of 1 714.481ms
 ✖ ⨯ Unable to compile TypeScript: src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist on type 'FastifyInstance<Server, IncomingMessage, ServerResponse, FastifyLoggerInstance>'.

 FAIL  test/routes/example.test.ts 1 failed of 1 727.771ms
 ✖ ⨯ Unable to compile TypeScript: src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist on type 'FastifyInstance<Server, IncomingMessage, ServerResponse, FastifyLoggerInstance>'.


                         
  🌈 SUMMARY RESULTS 🌈  
                         

 FAIL  test/routes/example.test.ts 1 failed of 1 727.771ms
 ✖ ⨯ Unable to compile TypeScript: src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist on type 'FastifyInstance<Server, IncomingMessage, ServerResponse, FastifyLoggerInstance>'.

 FAIL  test/routes/root.test.ts 1 failed of 1 714.481ms
 ✖ ⨯ Unable to compile TypeScript: src/plugins/aaa.ts(7,33): error TS2339: Property 'someSupport' does not exist on type 'FastifyInstance<Server, IncomingMessage, ServerResponse, FastifyLoggerInstance>'.

Suites:   2 failed, 1 passed, 3 of 3 completed
Asserts:  2 failed, 1 passed, of 3
Time:     3s
--------------|----------|----------|----------|----------|-------------------|
File          |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
--------------|----------|----------|----------|----------|-------------------|
All files     |       80 |      100 |       50 |       80 |                   |
 src          |      100 |      100 |      100 |      100 |                   |
  app.ts      |      100 |      100 |      100 |      100 |                   |
 src/plugins  |    69.23 |      100 |       40 |    69.23 |                   |
  sensible.ts |       75 |      100 |        0 |       75 |                10 |
  support.ts  |      100 |      100 |      100 |      100 |                   |
  zzz.ts      |       40 |      100 |        0 |       40 |             6,7,8 |
--------------|----------|----------|----------|----------|-------------------|

To Reproduce

1. Add plugins:

// src/plugins/aaa.ts

import fp from "fastify-plugin";

export default fp(async (fastify, opts) => {
  fastify.decorate("aaa", function () {
    console.log(`aaa: ${fastify.someSupport()}`);
    return "aaa";
  });
});

declare module "fastify" {
  export interface FastifyInstance {
    aaa(): string;
  }
}

// src/plugins/zzz.ts

import fp from "fastify-plugin";

export default fp(async (fastify, opts) => {
  fastify.decorate("zzz", function () {
    console.log(`zzz: ${fastify.someSupport()}`);
    return "zzz";
  });
});

declare module "fastify" {
  export interface FastifyInstance {
    zzz(): string;
  }
}

2. npm test

Expected behavior

❯ npm test

> fastify@1.0.0 test
> npm run build:ts && tsc -p test/tsconfig.test.json && tap test/**/*.test.ts


> fastify@1.0.0 build:ts
> tsc

 PASS  test/plugins/support.test.ts 1 OK 18.072ms
 PASS  test/routes/root.test.ts 1 OK 862.72ms
 PASS  test/routes/example.test.ts 1 OK 867.332ms

                         
  🌈 SUMMARY RESULTS 🌈  
                         

Suites:   3 passed, 3 of 3 completed
Asserts:  3 passed, of 3
Time:     3s

...

Your Environment

• node version: 14.16.0
• fastify version: 3.0.0
• os: Mac

[mcollina]

cc @fastify/typescript

[climba03003]

The problem is TypeScript do not know which file is imported when using fastify-autoload, so the type is not merged in this case.
I think you should use typeRoots or types options in tsconfig.json and move the typings to another file.