Use of npm instead of yarn fails

Hello guys, first time trying projen. I would like to create a CDK V2 TypeScript project with npm (I don’t have yarn installed). I first had much trouble finding how to use npm instead of yarn. It is actually implemented but not documented (yet?): --package-manager npm

So using projen latest version, I executed this command to generate the project:

npx projen new awscdk-app-ts --package-manager npm --projenrc-ts --cdk-version v2.0.0-rc.1

So far, so good. The project is generated. However, when I try to build it with the build npm script, I get this error:

> Executing task: npm run build <


> aws-codepipeline-custom-trigger-cdk@0.0.0 build
> npx projen build

🤖 build | npx projen
🤖 default | ts-node .projenrc.ts
🤖 Synthesizing project...
🤖 yarn install --check-files
Error: Command failed: yarn install --check-files
/bin/sh: yarn: command not found

    at checkExecSyncError (child_process.js:616:11)
    at Object.execSync (child_process.js:652:15)
    at Object.exec (/Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk/node_modules/projen/src/util.ts:10:24)
    at NodePackage.postSynthesize (/Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk/node_modules/projen/src/node-package.ts:646:5)
    at AwsCdkTypeScriptApp.synth (/Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk/node_modules/projen/src/project.ts:395:14)
    at Object.<anonymous> (/Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk/.projenrc.ts:16:9)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
    at Module.m._compile (/Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk/node_modules/ts-node/src/index.ts:1056:23)
    at Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
    at Object.require.extensions.<computed> [as .ts] (/Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk/node_modules/ts-node/src/index.ts:1059:12)
🤖 Synthesis failed: Task "default" failed when executing "ts-node .projenrc.ts" (cwd: /Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk)
🤖 Task "build" failed when executing "npx projen" (cwd: /Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk)
npm ERR! code 1
npm ERR! path /Users/ajo/Projects/Tests/aws-codepipeline-custom-trigger-cdk
npm ERR! command failed
npm ERR! command sh -c npx projen build

So, it looks like a bunch of scripts (found in the .projen/tasks.json file) use yarn instead of npm (well, actually there is no reference at all to npm in these scripts).

Should I conclude that npm is not (yet) supported ?

Thanks !

[mmcculloh-dms]

As a workaround for /bin/sh: yarn: command not found, if you use --no-post you can avoid the post install that would normally fail without yarn:

npx projen new awscdk-app-ts --projenrc-ts --cdk-version v2.0.0-rc.1 --no-post

So you can change the package manager in .projenrc.ts manually before running anything. Make sure to run npm i before npm run projen as you’ll need ts-node.

[Chriscbr]

So the question is: how do I bootstrap a project with npm ?

For now I think the first way you listed (with --package-manager npm) is the most correct – you just have to manually update .projenrc.ts after you get started.

I forgot about this before, but if you run npx projen new awscdk-app-ts --help, it don’t actually show the --package-manager option because it isn’t explicitly supported – this is because of a small technical issue. (Right now only string, number, and boolean typed options are accepted as CLI args, because we support projenrc files in multiple languages). It could be possible to fix this, but it requires taking a closer look at how we are processing arguments and using jsii.