How to build multiple projects simultaneously using Bazel build tool

To build the entire multi-language project with both Node.js and Python components using Bazel, you need to ensure that your BUILD files and WORKSPACE file are correctly configured. Then, you can use Bazel commands to build and test the whole project.

Step-by-Step Guide to Build the Entire Project

1. Ensure Your Project Structure is Correct:

   multi_language_project/
   ├── WORKSPACE
   ├── nodejs_project/
   │   ├── BUILD
   │   ├── package.json
   │   ├── package-lock.json
   │   └── src/
   │       └── index.js
   └── python_project/
       ├── BUILD
       ├── app.py
       └── lib/
           └── my_module.py
   

2. Example WORKSPACE File:

   workspace(name = "multi_language_project")
   
   # Load npm repository rules
   load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
   
   http_archive(
       name = "rules_nodejs",
       urls = ["https://github.com/bazelbuild/rules_nodejs/releases/download/4.3.2/rules_nodejs-4.3.2.tar.gz"],
       sha256 = "f0ad6a9573498482e5447a3b0958b8c2b1f02b640dd3a5099a1d7584f4a313d1",
       strip_prefix = "rules_nodejs-4.3.2",
   )
   
   load("@rules_nodejs//node:repositories.bzl", "node_repositories")
   node_repositories()
   
   # Load Python repository rules
   http_archive(
       name = "rules_python",
       urls = ["https://github.com/bazelbuild/rules_python/releases/download/0.1.0/rules_python-0.1.0.tar.gz"],
       sha256 = "c3d889a8364d7b0bc5df77d32e61b4b4afdafd2822c2297de6adbd0e1de2c639",
   )
   
   load("@rules_python//python:repositories.bzl", "py_repositories")
   py_repositories()
   

3. Example BUILD File for Node.js Sub-Project:

   # nodejs_project/BUILD
   
   load("@rules_nodejs//node:defs.bzl", "nodejs_binary", "npm_package")
   
   npm_package(
       name = "node_modules",
       package_json = "package.json",
       package_lock_json = "package-lock.json",
   )
   
   nodejs_binary(
       name = "app",
       entry_point = "src/index.js",
       data = ["//nodejs_project:node_modules"],
   )
   

4. Example BUILD File for Python Sub-Project:

   # python_project/BUILD
   
   load("@rules_python//python:defs.bzl", "py_binary", "py_library")
   
   py_library(
       name = "lib",
       srcs = glob(["lib/**/*.py"]),
   )
   
   py_binary(
       name = "app",
       srcs = ["app.py"],
       deps = [":lib"],
   )
   

5. Build and Run Commands:

   You can build and run individual sub-projects or the entire project using Bazel commands.

   • To build the entire project, you can specify the top-level targets in each sub-project:

     bazel build //nodejs_project:app //python_project:app
     

   • To run the applications, use the bazel run command for each sub-project:

     bazel run //nodejs_project:app
     bazel run //python_project:app
     

Building the Entire Project

To build the entire project, ensure you have all targets correctly defined in your BUILD files and then run:

bazel build //...

This command will build all targets in your workspace, which includes both the Node.js and Python sub-projects.

Running the Entire Project

If you have multiple entry points and want to run them, you need to run each separately:

bazel run //nodejs_project:app
bazel run //python_project:app