module 'tslib' cannot be found when importing from a sibling directory

[birtles]

What happens and why it is wrong

This is similar to issue #12, #214, and #216 but none of the solutions mentioned there worked for me and I have clear steps to reproduce so I hope this bug is helpful.

Steps to reproduce:

1. git clone https://github.com/birtles/rollup-ts-mono
2. cd rollup-ts-mono/a
3. yarn install
4. yarn build

Expected results: it builds successfully.

Actual results:

[!] (plugin rpt2) Error: ../common/func.ts:1:24 - error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.

1 export function func({ a }: { a: string }) {

Note that:

• npx tsc works
• A more complex setup with ts-jest works (i.e. yarn test works but npx rollup -c produces the above error)
• This setup deliberately doesn't include node-resolve etc. since I don't want the external dependencies to be bundled into the result. (This is for building an AWS lambda function where the node_modules will be uploaded along with the compiled file and keeping the compiled file smaller makes debugging easier.)
• The directory structure is quite inflexible due to this all being run through sam-cli
• It all worked fine until I started to use fancy syntax in the common/func.ts file
• Adding a root tsconfig.json and extending from it doesn't seem to make a difference
• Tweaking paths and baseUrl as per this comment can seem to help, but appears to break other things.

Environment

Node v12.14.0 running on Ubuntu 18.04 under WSL 1.

Versions

• typescript: 3.9.5
• rollup: 2.15.0
• rollup-plugin-typescript2: 0.27.1

rollup.config.js

import typescript from 'rollup-plugin-typescript2';

export default {
  input: './index.ts',
  output: {
    file: 'index.js',
    format: 'cjs',
  },
  plugins: [
    typescript({
      include: ['*.ts', '../common/*.ts'],
      verbosity: 3,
    }),
  ],
};

tsconfig.json

{
  "compilerOptions": {
    "alwaysStrict": true,
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "module": "ESNext",
    "moduleResolution": "node",
    "noImplicitAny": true,
    "noImplicitReturns": true,
    "noUnusedLocals": true,
    "pretty": true,
    "strictNullChecks": true,
    "target": "es2018"
  },
  "include": [
    "./*.ts",
    "../common/*.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

package.json

{
  "name": "a",
  "version": "1.0.0",
  "main": "index.ts",
  "license": "MIT",
  "scripts": {
    "build": "rollup -c"
  },
  "devDependencies": {
    "rollup": "^2.15.0",
    "rollup-plugin-typescript2": "^0.27.1",
    "typescript": "^3.9.5"
  }
}

plugin output with verbosity 3

log:

yarn run v1.22.4
$ rollup -c

./index.ts → index.js...
rpt2: built-in options overrides: {
    "noEmitHelpers": false,
    "importHelpers": true,
    "noResolve": false,
    "noEmit": false,
    "inlineSourceMap": false,
    "outDir": "/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/placeholder",
    "moduleResolution": 2,
    "allowNonTsExtensions": true
}
rpt2: parsed tsconfig: {
    "options": {
        "alwaysStrict": true,
        "allowSyntheticDefaultImports": true,
        "esModuleInterop": true,
        "module": 99,
        "moduleResolution": 2,
        "noImplicitAny": true,
        "noImplicitReturns": true,
        "noUnusedLocals": true,
        "pretty": true,
        "strictNullChecks": true,
        "target": 5,
        "configFilePath": "/c/Users/Brian/rollup-ts-mono/a/tsconfig.json",
        "noEmitHelpers": false,
        "importHelpers": true,
        "noResolve": false,
        "noEmit": false,
        "inlineSourceMap": false,
        "outDir": "/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/placeholder",
        "allowNonTsExtensions": true
    },
    "fileNames": [
        "/c/Users/Brian/rollup-ts-mono/a/index.ts",
        "/c/Users/Brian/rollup-ts-mono/common/func.ts"
    ],
    "typeAcquisition": {
        "enable": false,
        "include": [],
        "exclude": []
    },
    "raw": {
        "compilerOptions": {
            "alwaysStrict": true,
            "allowSyntheticDefaultImports": true,
            "esModuleInterop": true,
            "module": "ESNext",
            "moduleResolution": "node",
            "noImplicitAny": true,
            "noImplicitReturns": true,
            "noUnusedLocals": true,
            "pretty": true,
            "strictNullChecks": true,
            "target": "es2018"
        },
        "include": [
            "./*.ts",
            "../common/*.ts"
        ],
        "exclude": [
            "node_modules"
        ],
        "compileOnSave": false
    },
    "errors": [],
    "wildcardDirectories": {
        "/c/Users/Brian/rollup-ts-mono/a": 0,
        "/c/Users/Brian/rollup-ts-mono/common": 0
    },
    "compileOnSave": false,
    "configFileSpecs": {
        "includeSpecs": [
            "./*.ts",
            "../common/*.ts"
        ],
        "excludeSpecs": [
            "node_modules"
        ],
        "validatedIncludeSpecs": [
            "./*.ts",
            "../common/*.ts"
        ],
        "validatedExcludeSpecs": [
            "node_modules"
        ],
        "wildcardDirectories": {
            "/c/Users/Brian/rollup-ts-mono/a": 0,
            "/c/Users/Brian/rollup-ts-mono/common": 0
        }
    }
}
rpt2: typescript version: 3.9.5
rpt2: tslib version: 1.11.2
rpt2: rollup version: 2.15.0
rpt2: rollup-plugin-typescript2 version: 0.27.1
rpt2: plugin options:
{
    "include": [
        "*.ts",
        "../common/*.ts"
    ],
    "verbosity": 3,
    "check": true,
    "clean": false,
    "cacheRoot": "/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2",
    "exclude": [
        "*.d.ts",
        "**/*.d.ts"
    ],
    "abortOnError": true,
    "rollupCommonJSResolveHack": false,
    "useTsconfigDeclarationDir": false,
    "tsconfigOverride": {},
    "transformers": [],
    "tsconfigDefaults": {},
    "objectHashIgnoreUnknownHack": false,
    "cwd": "/c/Users/Brian/rollup-ts-mono/a",
    "typescript": "version 3.9.5"
}
rpt2: rollup config:
{
    "external": [],
    "input": "./index.ts",
    "plugins": [
        {
            "name": "rpt2"
        },
        {
            "name": "stdin"
        }
    ],
    "output": [
        {
            "file": "index.js",
            "format": "cjs",
            "plugins": []
        }
    ]
}
rpt2: tsconfig path: /c/Users/Brian/rollup-ts-mono/a/tsconfig.json
rpt2: included:
[
    "*.ts",
    "../common/*.ts"
]
rpt2: excluded:
[
    "*.d.ts",
    "**/*.d.ts"
]
rpt2: Ambient types:
rpt2:     /c/Users/Brian/rollup-ts-mono/a/node_modules/@types/estree/index.d.ts
rpt2: ambient types changed, redoing all semantic diagnostics
rpt2: transpiling '/c/Users/Brian/rollup-ts-mono/a/index.ts'
rpt2:     cache: '/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/rpt2_86652b882e81b012e213895c8bb1ed1d48aba191/code/cache/42dd2afd58080ad46e2f26195c4b76ce6ba22e63'
rpt2:     cache miss
rpt2:     cache: '/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/rpt2_86652b882e81b012e213895c8bb1ed1d48aba191/syntacticDiagnostics/cache/42dd2afd58080ad46e2f26195c4b76ce6ba22e63'
rpt2:     cache miss
rpt2:     cache: '/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/rpt2_86652b882e81b012e213895c8bb1ed1d48aba191/semanticDiagnostics/cache/42dd2afd58080ad46e2f26195c4b76ce6ba22e63'
rpt2:     cache miss
rpt2: dependency '/c/Users/Brian/rollup-ts-mono/common/func.ts'
rpt2:     imported by '/c/Users/Brian/rollup-ts-mono/a/index.ts'
rpt2: resolving '../common/func' imported by '/c/Users/Brian/rollup-ts-mono/a/index.ts'
rpt2:     to '/c/Users/Brian/rollup-ts-mono/common/func.ts'
rpt2: transpiling '/c/Users/Brian/rollup-ts-mono/common/func.ts'
rpt2:     cache: '/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/rpt2_86652b882e81b012e213895c8bb1ed1d48aba191/code/cache/154c4f09b6a8aebbd439964a86673337ca5a9381'
rpt2:     cache miss
rpt2:     cache: '/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/rpt2_86652b882e81b012e213895c8bb1ed1d48aba191/syntacticDiagnostics/cache/154c4f09b6a8aebbd439964a86673337ca5a9381'
rpt2:     cache miss
rpt2:     cache: '/c/Users/Brian/rollup-ts-mono/a/node_modules/.cache/rollup-plugin-typescript2/rpt2_86652b882e81b012e213895c8bb1ed1d48aba191/semanticDiagnostics/cache/154c4f09b6a8aebbd439964a86673337ca5a9381'
rpt2:     cache miss
[!] (plugin rpt2) Error: ../common/func.ts:1:24 - error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.

1 export function func({ a }: { a: string }) {
                         ~

../common/func.ts
Error: ../common/func.ts:1:24 - error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.

1 export function func({ a }: { a: string }) {
                         ~

    at error (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup/dist/shared/rollup.js:213:30)
    at throwPluginError (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup/dist/shared/rollup.js:17117:12)
    at Object.error (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup/dist/shared/rollup.js:17911:24)
    at Object.error (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup/dist/shared/rollup.js:17290:38)
    at RollupContext.error (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup-plugin-typescript2/dist/rollup-plugin-typescript2.cjs.js:17195:30)
    at /c/Users/Brian/rollup-ts-mono/a/node_modules/rollup-plugin-typescript2/dist/rollup-plugin-typescript2.cjs.js:24992:19
    at arrayEach (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup-plugin-typescript2/dist/rollup-plugin-typescript2.cjs.js:535:11)
    at forEach (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup-plugin-typescript2/dist/rollup-plugin-typescript2.cjs.js:9361:14)
    at printDiagnostics (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup-plugin-typescript2/dist/rollup-plugin-typescript2.cjs.js:24968:5)
    at Object.transform (/c/Users/Brian/rollup-ts-mono/a/node_modules/rollup-plugin-typescript2/dist/rollup-plugin-typescript2.cjs.js:29071:17)

error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[birtles]

• It all worked fine until I started to use fancy syntax in the common/func.ts file

Just to clarify what I mean by this, if I change:

export function func({ a }: { a: string }) {
  console.log(`Hi ${a}`);
}

to:

export function func(a: string) {
  console.log(`Hi ${a}`);
}

it all works as intended.

[birtles]

FWIW, I think I may have worked around this by adding a package.json to common, adding tslib as a dependency there, and adding a preinstall step to each of the sibling directories to make them run npm install in common if it exists (since it won't when run under sam build).

[SagnikPradhan]

I guess it is the same reason why my wrapper for rollup throws the same error when I changed tslib from a peer dependency to dependency. For side note, I am not using this plugin. 😅 It was the official plugin.

[agilgur5]

• It all worked fine until I started to use fancy syntax in the common/func.ts file

This makes sense as newer syntax is not implemented in older versions of ECMAScript and so a "helper" is needed to basically "polyfill" the syntax. TS has its helpers in the tslib library.
Note that Babel has equivalent functionality for older versions with @babel/runtime, which is a similar set of helpers.

Basically, if the syntax you're using isn't supported by your target version, a helper must be imported from tslib.

• git clone https://github.com/birtles/rollup-ts-mono
• Tweaking paths and baseUrl as per this comment can seem to help, but appears to break other things.
• typescript: 3.9.5

I checked out the repo and was able to reproduce this. I read the upstream issue linked and this seems to have been solved within TS itself later in that same issue: microsoft/TypeScript#37991 (comment) (PR: microsoft/TypeScript#43166).

Upgrading to a newer version of TS (at least v4.3? per the milestones mentioned there) makes this issue go away. For instance, I upgraded to TS 4.6.5 in your project and there was no error anymore.

It's written there that the issue is due to a "weak check" for the syntax. Your target, es2018, doesn't actually need a helper -- you'll see after running yarn build that the resulting bundled index.js doesn't actually have any imports.

FWIW, I think I may have worked around this by adding a package.json to common, adding tslib as a dependency there

This also makes sense as a workaround, as then TS would be able to find tslib in common.
Otherwise, you don't have a root package.json with tslib in the root's node_modules, nor one in common, so Node's resolution algorithm would be unable to find it. Node's resolution algorithm doesn't check sibling directories, it checks parent directories.