> ## Documentation Index
> Fetch the complete documentation index at: https://site.aspect.build/llms.txt
> Use this file to discover all available pages before exploring further.

# Outputs in the source tree

> Learn when Bazel rules should write outputs into the source tree so editors and IDEs can find generated files like ts_proto_library type definitions.

Output files from Bazel spawns are always written beneath the `bazel-out` tree.

But other tools allow, or even expect, that files are present in the source tree. This is frequently observed with Editors and IDEs for example.

We can un-break the situation if we relax the Bazel dogma around writing to the source tree.

For example, in the `logger/schema` folder we should have a `ts_proto_library` target which produces a `logger_pb.d.ts` interface definition file. The editor expects to read that file in order to provide valuable completion (intellisense) to a developer navigating the API.

`ts_proto_library` is a macro which automatically writes this file to the source tree, which we can observe by deleting it and then running the tests in that package.

> There are options to "teach the editor" instead. In Go for example,
> it's possible to use the GoPackagesDriver to teach the editor to look in bazel-out
> for logger.pb.go. But, this is a difficult, brittle configuration to setup on developer machines.
> And then you'll just have the next tool or language where the bazel-out location breaks things.

Of course, `bazel build` itself cannot result in files in the source tree, but we can get a close
approximation with a rule called [`write_source_files`](https://github.com/bazel-contrib/bazel-lib/blob/main/docs/write_source_files.md).

It uses a simple pattern:

* the build target writes to a file like `bazel-out/pkg/foo.pb.go`
* a generated test target asserts that `pkg/foo.pb.go` in the source folder has the same content
* a generated executable copies files from `bazel-out` back to the source tree
* when the test fails, it prints an instruction how the developer can run the executable

This is the same pattern we use for "golden" or "snapshot" files which live in the source tree.

<Note>
  Read more about this pattern: [bazel can write to the source folder](/blog/bazel-can-write-to-the-source-folder)
</Note>