RFC: Run prepare Scripts for Linked Bundled Dependencies

accepted/0000-prepare-linked-bundled-deps-during-pack.md

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+# Run `prepare` Scripts for Linked Bundled Dependencies
+
+## Summary
+
+Following discussion on [#477](https://github.com/npm/rfcs/issues/477) and previously on [#463](https://github.com/npm/rfcs/issues/463), workspaces that depend on sibling workspaces via the `file:` protocol (a.k.a. linked or symlinked dependencies) should run the sibling workspaces' `prepare` scripts as part of the depend-_ing_ workspace's `pack` operation when those sibling dependencies are also specified as bundle/d dependencies (e.g. their "built" output should make it into the packed workspace's tarball).
+
+## Motivation
+
+It's common for workspaces in a monorepo to depend on one another. Calling `npm pack` on a workspace should automatically run the `prepare` script of any linked and bundled dependencies so that the produced tarball will have consistent and correct contents without a bunch of extra wiring.
+
+## Detailed Explanation
+
+`app-a` and `pkg-b` are workspaces in a monorepo. `app-a` depends on `pkg-b` and lists it as a `bundledDependency` because `app-a` is expected to be distributed as a Node app somewhere (AWS Lambda, Docker, etc.) where it should be deployed along with its production dependencies. `pkg-b` is not published to a registry for reasons, and is written in a language or standard that must be compiled or transpiled to be runnable in Node (TypeScript, ES2049, etc.).
+
+Assuming `app-a`s package.json contains this:
+
+```json
+{
+  "name": "app-a",
+  "version": "1.0.0",
+  "dependencies": {
+    "pkg-b": "file:../pkg-b"
+  },
+  "bundleDependencies": ["pkg-b"]
+}
+```
+
+… and `pkg-b`'s package.json contains this:
+
+```json
+{
+  "name": "pkg-b",
+  "version": "1.0.0",
+  "scripts": {
+    "prepare": "tsc"
+  }
+}
+```
+
+… with the appropriate tsconfig.json, .npmignore, and index.ts in `pkg-b`, running `cd app-a ; npm i --package-lock=false ; npm pack` should produce a tarball with contents like:
+
+```sh
+app-a
+├── node_modules
+│   └── pkg-b
+│        ├── index.js
+│        └── package.json
+└── package.json
+```
+
+## Rationale and Alternatives
+
+This functionality is possible today, but requires the package being packed to explicitly call the `prepare` scripts of each of its linked and bundled dependencies.
+
+It's also possible to achieve the same end result by publishing the bundled dependencies to a registry, but for a package that's expected to have utility only within the context of other workspaces in a monorepo this adds a bunch of bureacracy for not much benefit.
+
+## Implementation
+
+Need help with this part.
+
+> {{Give a high-level overview of implementation requirements and concerns. Be specific about areas of code that need to change, and what their potential effects are. Discuss which repositories and sub-components will be affected, and what its overall code effect might be.}}
+>
+> {{THIS SECTION IS REQUIRED FOR RATIFICATION -- you can skip it if you don't know the technical details when first submitting the proposal, but it must be there before it's accepted}}
+
+## Prior Art
+
+- Related to a forthcoming PR about workspace/dependency layout from @ljharb
+- Discussed at [#478](https://github.com/npm/rfcs/issues/478)
+
+## Unresolved Questions and Bikeshedding
+
+I don't think there's anything here, but leaving it for now in case I've missed/forgotten something.
+
+> {{Write about any arbitrary decisions that need to be made (syntax, colors, formatting, minor UX decisions), and any questions for the proposal that have not been answered.}}
+>
+> {{THIS SECTION SHOULD BE REMOVED BEFORE RATIFICATION}}