Needlessly Provoking Marsupials


    9.0.3 • Public • Published


    This module contains a set of common scripts and default configurations to build LoopBack 4 or other TypeScript modules, including:

    • lb-tsc: Use tsc to compile typescript files
    • lb-eslint: Run eslint
    • lb-prettier: Run prettier
    • lb-mocha: Run mocha to execute test cases
    • lb-nyc: Run nyc

    These scripts first try to locate the CLI from target project dependencies and fall back to bundled ones in @loopback/build.

    Basic use

    To use @loopback/build for your package:

    1. Run the following command to add @loopback/build as a dev dependency.

    npm i @loopback/build --save-dev

    1. Configure your project package.json as follows:
    "scripts": {
        "build": "lb-tsc",
        "build:watch": "lb-tsc --watch",
        "clean": "lb-clean",
        "lint": "npm run prettier:check && npm run eslint",
        "lint:fix": "npm run prettier:fix && npm run eslint:fix",
        "prettier:cli": "lb-prettier \"**/*.ts\" \"**/*.js\"",
        "prettier:check": "npm run prettier:cli -- -l",
        "prettier:fix": "npm run prettier:cli -- --write",
        "eslint": "lb-eslint --report-unused-disable-directives .",
        "eslint:fix": "npm run eslint -- --fix",
        "pretest": "npm run clean && npm run build",
        "test": "lb-mocha \"dist/__tests__\"",
        "posttest": "npm run lint",
        "start": "npm run build && node .",
        "prepublishOnly": "npm run test"

    Please remember to replace your-module-name with the name of your module.

    Now you run the scripts, such as:

    • npm run build - Compile TypeScript files and copy resources (non .ts files) to outDir
    • npm test - Run all mocha tests
    • npm run lint - Run eslint and prettier on source files
    1. Override default configurations in your project
    • lb-tsc

      By default, lb-tsc searches your project's root directory for then tsconfig.json. If neither of them exists, a tsconfig.json will be created to extend from @loopback/build/config/tsconfig.common.json.

      To customize the configuration:

      • Create or tsconfig.json in your project's root directory

          "$schema": "",
          "extends": "@loopback/build/config/tsconfig.common.json",
          "compilerOptions": {
            "outDir": "dist",
            "rootDir": "src"
          "include": ["src"]
      • Set options explicitly for the script

        lb-tsc -p tsconfig.json --target es2017 --outDir dist

        For more information, see

      • The following un-official compiler options are available:

        Option Description
        --copy-resources Copy all non-typescript files from src and test to outDir, preserving their relative paths.
      • Using ttypescript

        Stability: ⚠️Experimental⚠️

        If you would like to use ttypescript and its available plugins, you can substitute lb-tsc with lb-ttsc, or pass the option lb-tsc --use-ttypescript. If ttypescript is not installed, the default TypeScript compiler tsc will be used instead.

    1. Run builds
    npm run build
    1. Run code coverage reports
    • lb-nyc

      lb-nyc is a simple wrapper for nyc.

      To customize the configuration:

      • Create .nycrc in your project's root directory

          "include": ["dist"],
          "exclude": ["dist/__tests__/"],
          "extension": [".js", ".ts"],
          "reporter": ["text", "html"],
          "exclude-after-remap": false
      • Update your package.json scripts:

        "precoverage": "npm test",
        "coverage": "open coverage/index.html",
        "coverage:ci": "lb-nyc report --reporter=text-lcov | coveralls",
        "test": "lb-nyc npm run mocha",
        "test:ci": "lb-nyc npm run mocha"

        coverage:ci sets up integration with Coveralls.

    A note on console logs printed by tests

    We consider (console) logging from tests as a bad practice, because such logs usually clutter the test output and make it difficult to distinguish legitimate error messages from the noise.

    By default, lb-mocha detects when the tests and/or the application tested have printed console logs and fails the test run with the following message:


    If you need more information about behavior in the test, then the first choice should be to use a better or more descriptive error assertion. If that's not possible, then use debug statements to print additional information when explicitly requested.

    A typical situation is that a test is sending an HTTP request and the server responds with an error code as expected. However, because the server is configured to log failed requests, it will print a log also for requests where the failure was expected and intentional. The solution is to configure your REST server to suppress error messages for that specific error code only. Our @loopback/testlab module is providing a helper createUnexpectedHttpErrorLogger that makes this task super easy.

    Alternatively, it's also possible to disable detection of console logs by calling lb-mocha with --allow-console-logs argument.



    run npm test from the root folder.


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    npm i @loopback/build

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