Bazel auto generate dependencies for ts_library

Question

Is it possible to auto-generate the dependencies of a bazel target? It seems like there should be a way to look at the imports of the module and know which bazel dependencies are needed at least in a lot of cases common cases. This could save a lot of boilerplate code.

load("@npm_bazel_typescript//:index.bzl", "ts_library")
ts_library(
    name = "lib",
    srcs = glob(include = ["**/*.ts"]),
    # Is there any easy way to generate this list?
    deps = [],
)

I know there are packages for Java that do this. https://github.com/johnynek/bazel-dep . I haven't been able to find anything for any other languages.

If it doesn't exist I think it could be pretty straightforward to write. Create a template file for you to work off of creating the real BUILD file. Then run typescript to pull the AST of the module. Look through the imports. The 3rd part imports will be easier since they should resolve to an npm module.

For other files that may or may not be in this library then there might be a way to query what package they live int. That could probably work. Any pointers would be very much appreciated.

Answer 1

Disclosure: I am one of the authors of this library.

https://github.com/evertz/bzlgen

It can generate BUILD files (or, more precisely it generates buildozer commands) for Angular (ng_module) and SCSS (scss_library and scss_binary) libs.

I've just moved this in to opensource from our internal repo. It works in a similar way to what you suggest, however it doesn't query for labels. It uses a file or directory as a starting point, parse into an AST, query the AST to fetch imports and reexports, convert the paths into labels.

Adding ts_library support is a logical next step.

It doesn't always get you a 100% working BUILD file currently, but it will get you ~80-90% of the way there, and do the boilerplate parts for you.

Another approach would be to interact with the Gazelle API, and manipulate the BUILD files directly.

A previous version of this tool generated the BUILD files from a string and it got difficult to work with when manipulating the files in other ways.