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Vue.js Contributing Guide

Hi! I'm really excited that you are interested in contributing to Vue.js. Before submitting your contribution, please make sure to take a moment and read through the following guidelines:

Issue Reporting Guidelines

Pull Request Guidelines

  • Checkout a topic branch from a base branch, e.g. master, and merge back against that branch.

  • If adding a new feature:

    • Add accompanying test case.
    • Provide a convincing reason to add this feature. Ideally, you should open a suggestion issue first and have it approved before working on it.
  • If fixing a bug:

    • If you are resolving a special issue, add (fix #xxxx[,#xxxx]) (#xxxx is the issue id) in your PR title for a better release log, e.g. update entities encoding/decoding (fix #3899).
    • Provide a detailed description of the bug in the PR. Live demo preferred.
    • Add appropriate test coverage if applicable. You can check the coverage of your code addition by running npm test -- --coverage.
  • It's OK to have multiple small commits as you work on the PR - GitHub can automatically squash them before merging.

  • Make sure tests pass!

  • Commit messages must follow the commit message convention so that changelogs can be automatically generated. Commit messages are automatically validated before commit (by invoking Git Hooks via yorkie).

  • No need to worry about code style as long as you have installed the dev dependencies - modified files are automatically formatted with Prettier on commit (by invoking Git Hooks via yorkie).

Development Setup

You will need Node.js version 10+, and PNPM.

We also recommend installing ni to help switching between repos using different package managers. ni also provides the handy nr command which running npm scripts easier.

After cloning the repo, run:

$ pnpm i # install the dependencies of the project

A high level overview of tools used:

Scripts

The examples below will be using the nr command from the ni package. You can also use plain npm run, but you will need to pass all additional arguments after the command after an extra --. For example, nr build runtime --all is equivalent to npm run build -- runtime --all.

nr build

The build script builds all public packages (packages without private: true in their package.json).

Packages to build can be specified with fuzzy matching:

# build runtime-core only
nr build runtime-core

# build all packages matching "runtime"
nr build runtime --all

Build Formats

By default, each package will be built in multiple distribution formats as specified in the buildOptions.formats field in its package.json. These can be overwritten via the -f flag. The following formats are supported:

  • global
  • esm-bundler
  • esm-browser
  • cjs

Additional formats that only apply to the main vue package:

  • global-runtime
  • esm-bundler-runtime
  • esm-browser-runtime

More details about each of these formats can be found in the vue package README and the Rollup config file.

For example, to build runtime-core with the global build only:

nr build runtime-core -f global

Multiple formats can be specified as a comma-separated list:

nr build runtime-core -f esm-browser,cjs

Build with Source Maps

Use the --sourcemap or -s flag to build with source maps. Note this will make the build much slower.

Build with Type Declarations

The --types or -t flag will generate type declarations during the build and in addition:

  • Roll the declarations into a single .d.ts file for each package;
  • Generate an API report in <projectRoot>/temp/<packageName>.api.md. This report contains potential warnings emitted by api-extractor.
  • Generate an API model json in <projectRoot>/temp/<packageName>.api.json. This file can be used to generate a Markdown version of the exported APIs.

nr dev

The dev script bundles a target package (default: vue) in a specified format (default: global) in dev mode and watches for changes. This is useful when you want to load up a build in an HTML page for quick debugging:

$ nr dev

> watching: packages/vue/dist/vue.global.js
  • Important: output of the dev script is for development and debugging only. While it has the same runtime behavior, the generated code should never be published to npm.

  • The dev script does not support fuzzy match - you must specify the full package name, e.g. nr dev runtime-core.

  • The dev script supports specifying build format via the -f flag just like the build script.

  • The dev script also supports the -s flag for generating source maps, but it will make rebuilds slower.

  • The dev script supports the -i flag for inlining all deps. This is useful when debugging esm-bundler builds which externalizes deps by default.

nr dev-compiler

The dev-compiler script builds, watches and serves the Template Explorer at http://localhost:5000. This is extremely useful when working on the compiler.

nr test

The test script simply calls the jest binary, so all Jest CLI Options can be used. Some examples:

# run all tests
$ nr test

# run all tests under the runtime-core package
$ nr test runtime-core

# run tests in a specific file
$ nr test fileName

# run a specific test in a specific file
$ nr test fileName -t 'test name'

The default test script includes the --runInBand jest flag to improve test stability, especially for the CSS transition related tests. When you are testing specific test specs, you can also run npx jest with flags directly to speed up tests (jest runs them in parallel by default).

Project Structure

This repository employs a monorepo setup which hosts a number of associated packages under the packages directory:

  • reactivity: The reactivity system. It can be used standalone as a framework-agnostic package.

  • runtime-core: The platform-agnostic runtime core. Includes code for the virtual dom renderer, component implementation and JavaScript APIs. Higher-order runtimes (i.e. custom renderers) targeting specific platforms can be created using this package.

  • runtime-dom: The runtime targeting the browser. Includes handling of native DOM API, attributes, properties, event handlers etc.

  • runtime-test: The lightweight runtime for testing. Can be used in any JavaScript environment since it "renders" a tree of plain JavaScript objects. The tree can be used to assert correct render output. Also provides utilities for serializing the tree, triggering events, and recording actual node operations performed during an update.

  • server-renderer: Package for server-side rendering.

  • compiler-core: The platform-agnostic compiler core. Includes the extensible base of the compiler and all platform-agnostic plugins.

  • compiler-dom: Compiler with additional plugins specifically targeting the browser.

  • compiler-sfc: Lower level utilities for compiling Vue Single File Components.

  • compiler-ssr: Compiler that produces render functions optimized for server-side rendering.

  • template-explorer: A development tool for debugging compiler output. You can run nr dev template-explorer and open its index.html to get a repl of template compilation based on current source code.

    A live version of the template explorer is also available, which can be used for providing reproductions for compiler bugs. You can also pick the deployment for a specific commit from the deploy logs.

  • shared: Internal utilities shared across multiple packages (especially environment-agnostic utils used by both runtime and compiler packages).

  • vue: The public facing "full build" which includes both the runtime AND the compiler.

Importing Packages

The packages can import each other directly using their package names. Note that when importing a package, the name listed in its package.json should be used. Most of the time the @vue/ prefix is needed:

import { h } from '@vue/runtime-core'

This is made possible via several configurations:

  • For TypeScript, compilerOptions.paths in tsconfig.json
  • For Jest, moduleNameMapper in jest.config.js
  • For plain Node.js, they are linked using PNPM Workspaces.

Package Dependencies

                                    +---------------------+
                                    |                     |
                                    |  @vue/compiler-sfc  |
                                    |                     |
                                    +-----+--------+------+
                                          |        |
                                          v        v
                      +---------------------+    +----------------------+
                      |                     |    |                      |
        +------------>|  @vue/compiler-dom  +--->|  @vue/compiler-core  |
        |             |                     |    |                      |
   +----+----+        +---------------------+    +----------------------+
   |         |
   |   vue   |
   |         |
   +----+----+        +---------------------+    +----------------------+    +-------------------+
        |             |                     |    |                      |    |                   |
        +------------>|  @vue/runtime-dom   +--->|  @vue/runtime-core   +--->|  @vue/reactivity  |
                      |                     |    |                      |    |                   |
                      +---------------------+    +----------------------+    +-------------------+

There are some rules to follow when importing across package boundaries:

  • Never use direct relative paths when importing items from another package - export it in the source package and import it at the package level.

  • Compiler packages should not import items from the runtime, and vice versa. If something needs to be shared between the compiler-side and runtime-side, it should be extracted into @vue/shared instead.

  • If a package (A) has a non-type import, or re-exports a type from another package (B), then (B) should be listed as a dependency in (A)'s package.json. This is because the packages are externalized in the ESM-bundler/CJS builds and type declaration files, so the dependency packages must be actually installed as a dependency when consumed from package registries.

Contributing Tests

Unit tests are collocated with the code being tested in each package, inside directories named __tests__. Consult the Jest docs and existing test cases for how to write new test specs. Here are some additional guidelines:

  • Use the minimal API needed for a test case. For example, if a test can be written without involving the reactivity system or a component, it should be written so. This limits the test's exposure to changes in unrelated parts and makes it more stable.

  • If testing platform agnostic behavior or asserting low-level virtual DOM operations, use @vue/runtime-test.

  • Only use platform-specific runtimes if the test is asserting platform-specific behavior.

Test coverage is continuously deployed at https://vue-next-coverage.netlify.app/. PRs that improve test coverage are welcome, but in general the test coverage should be used as a guidance for finding API use cases that are not covered by tests. We don't recommend adding tests that only improve coverage but not actually test a meaning use case.

Testing Type Definition Correctness

This project uses tsd to test the built definition files (*.d.ts).

Type tests are located in the test-dts directory. To run the dts tests, run nr test-dts. Note that the type test requires all relevant *.d.ts files to be built first (and the script does it for you). Once the d.ts files are built and up-to-date, the tests can be re-run by simply running nr test-dts.

Financial Contribution

As a pure community-driven project without major corporate backing, we also welcome financial contributions via Patreon and OpenCollective.

What's the difference between Patreon and OpenCollective funding?

Funds donated via Patreon go directly to support Evan You's full-time work on Vue.js. Funds donated via OpenCollective are managed with transparent expenses and will be used for compensating work and expenses for core team members or sponsoring community events. Your name/logo will receive proper recognition and exposure by donating on either platform.

Credits

Thank you to all the people who have already contributed to Vue.js!