ts-node with project references in a lerna monorepo

[kerdany]

I'm using lerna with typescript project references for a node application containing two packages. Package lib and package app (which depends on lib).

I've configured typescript project references so that package lib is built automatically whenever we run tsc --build inside package app (i.e. to build for production).

Here's how the tsconfig.json files are configured for each of the packages:

packages/lib/tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "rootDir": "src",
    "outDir": "dist",
    "tsBuildInfoFile": "dist/.tsbuildinfo",
    "composite": true
  }
}

packages/app/tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "rootDir": "src",
    "outDir": "dist",
    "tsBuildInfoFile": "dist/.tsbuildinfo",
    "incremental": true
  },
  "references": [
    { "path": "../lib" }
  ]
}

Currently, running tsc --build (inside app) compiles typescript to javascript in the dist directory in each of app and lib perfectly fine, the setup runs flawlessly in production mode.

The problem, however, is that trying to run the project in development with ts-node via nodemon --exec 'ts-node src/index.ts' in development fires the following error:

/path/to/packages/app/node_modules/ts-node/src/index.ts:245
    return new TSError(diagnosticText, diagnosticCodes)
           ^
TSError: ⨯ Unable to compile TypeScript:
src/index.ts(1,23): error TS2307: Cannot find module '@myproj/lib'.
...

What seems to be happening, is that ts-node is looking for the @myproj/lib package inside node_modules directory (symlinked by lerna), instead of compiling it on the fly through typetcript's project references, as is setup inside both tsconfig.json files.

I validated my theory by:

• Running a regular tsc --build first (which also builds the lib/dist code).
• Then running nodemon --exec 'ts-node src/index.ts' again, and it ran fine then.

Which means that ts-node in this case is loading lib via the compiled .js code inside lib/dist (symlinked by lerna), NOT via compiling its .ts code on the fly (via references).

I'm using ts-node@8.4.1 (currently the latest version).

Some questions:

• Doesn't ts-node currently support project-references yet or passing the --build flag to tsc yet?

• Am I doing something wrong in my (e.g. tsconfig.json) configurations that's causing ts-node not to compile/build lib.

• I can see that a new --build flag is being added to ts-node in the master branch (commit), but it seems that it's irrelevant to tsc's --build flag.

Note: Currently I'm working around this (without ts-node) via nodemon --exec 'tsc --build && node dist/index.js' till I get this figured out.

Thanks!

[blakeembrey]

1. I don't think so, though I can replicate project references working for other cases. It's using the language services API today which has typically had no problems, but I'd have to ask if you can build a simple repro for me to work with on this to confirm.
2. I don't think so, more likely that references don't work as expected.
3. Correct, I can probably rename to --emit to clarify the use-case. However, I run into issues with project references on the latest master build that need to be fixed (so your example might help me too) 😦

[kerdany]

Thanks @blakeembrey

1. Sure, I will prepare a sample repo to reproduce the issue first thing in the morning (UTC+2 here).

Thanks!

[kerdany]

Hi again,
I've created code to reproduce issue here:
https://github.com/kerdany/ts-node_issue-897

[blakeembrey]

@kerdany Thanks! Interestingly I get the same error in development with VS Code and tsc, until I enable --build. This makes sense, since I assume that TypeScript is actually building references first when you specify --build. It does make it trickier for ts-node though, I guess it should also build those dependencies somehow. We might have to do something in memory to make this possible...

[blakeembrey]

Another interesting part of this is that it's related to node and TypeScript's understanding of module resolution. You can actually make this work with the current release of ts-node by importing directly the other .ts file:

import { greet } from "@myproj/lib/src/index";

Edit: Don't expect this to work in the next major version though, I've been having a lot of trouble with getting project references working and this also fails with VS Code tsc.

[jomi-se]

Have you done any progress or got any clues for this? I just ran into the same issue as well

[impaler]

I also ran into this trying out packages in yarn workspaces. When wanting to debug with node -r ts-node/register as a work around for now I am composing a root tsconfig.json with all relevant references and running a tsc --build --watch running separately. Would be great to have project references resolve and build with ts-node alone.

[nickzelei]

FYI it looks like they've added API support for building project references.

microsoft/TypeScript#31432

interface SolutionBuilder<T extends BuilderProgram> {
    build(project?: string, cancellationToken?: CancellationToken): ExitStatus;
    clean(project?: string): ExitStatus;
    buildReferences(project: string, cancellationToken?: CancellationToken): ExitStatus;
    cleanReferences(project?: string): ExitStatus;
    getNextInvalidatedProject(cancellationToken?: CancellationToken): InvalidatedProject<T> | undefined;
}

[krzkaczor]

FYI: the obvious workaround is to set TS_NODE_TRANSPILE_ONLY=true but then you won't get any type checks.

[dchambers]

@krzkaczor, I tried setting this on the command line (using --transpile-only and -T) and it makes no difference -- project references still aren't built.

[dchambers]

I ended up using concurrently to build the project references for all the libraries within our monorepo (all inside a lib directory) like so:

"scripts": {
  "start": "concurrently \"tsc -b -w ../lib\" \"nodemon -w ./src -w ../lib --ignore 'lib/*/src/*' -e js,jsx,gql,ts,tsx --exec ts-node src/server.ts\"",
}

Here, the lib directory contained a tsconfig.json with references to all the composite projects within the directory.