`export * from …` sometimes behaves differently in `tsgo` than in `tsc` or `tsgo` LSP

[chriskrycho]

Steps to reproduce

In a private monorepo setup, when invoking tsgo against a package that depends on another package in the repo, an import fails to resolve when it is looking up a type that is re-exported with the export * from syntax. It resolves correctly with tsc v5.9.3 and using the language server supplied with @typescript/native-preview (same correct behavior in both the official VS Code preview extension and Zed’s experimental extension wrapping the native LSP).

The original export is a simple function export:

export function stubDynamicConfig<T>(config: DynamicConfiguration<T>): {
  setValue: (value: T) => void;
} {
  // ...
}

The re-export is written like this, using an import map to map the location relative to this package:

export * from "#feature-flags/dynamic-configuration/dynamic-config-harness.testutil.ts";

The import is written like this, relying on an export map in the exporting package to resolve the location:

import { stubDynamicConfig } from "@vanta/feature-flags/dynamic-config/testing";

Both packages are using "type": "commonjs" implicitly by leaving type unset.

Project tsconfig.json

{
  "extends": "../../tsconfig.base.apps.json",
  "compilerOptions": {
    "rootDir": "src",
    "outDir": "dist",
    "exactOptionalPropertyTypes": false
  },
  "references": [
    { "path": "../../packages/common" },
    { "path": "../../packages/codegen-common" },
    { "path": "../../packages/core-infra" },
    { "path": "../../packages/core-product" },
    { "path": "../../packages/event-schema" },
    { "path": "../../packages/event-streaming" },
    { "path": "../../packages/feature-flags" },
    { "path": "../../packages/god-objects" },
    { "path": "../../packages/server-common" },
    { "path": "../../packages/tag" },
    { "path": "../../packages/teams" },
    { "path": "../../packages/penetration-test" },
    { "path": "../../packages/uploaded-document" }
  ],
  "include": ["../../packages/ts-reset/**/*.d.ts", "src/**/*.ts"],
  "exclude": ["**/node_modules", "src/cli.ts"]
}

The referenced tsconfig.base.apps.json

{
  "extends": "./tsconfig.base.json",
  "compilerOptions": {
    "noEmit": true,
    "composite": false
  }
}

The referenced tsconfig.base.json

{
  "compilerOptions": {
    // Module resolution options
    "module": "node20",
    "resolveJsonModule": true,
    "esModuleInterop": true,
    // Typechecking options
    "exactOptionalPropertyTypes": true,
    "strict": true,
    "noImplicitReturns": true,
    "noImplicitOverride": true,
    "noUncheckedIndexedAccess": true,
    "noUnusedLocals": true,
    "noFallthroughCasesInSwitch": true,
    "allowUnreachableCode": false,
    "useUnknownInCatchVariables": true,
    "target": "es2023",
    "lib": ["es2023", "ESNext.Collection", "ESNext.Iterator"],
    "types": ["node", "mocha"],
    "experimentalDecorators": true,
    // Performance-related options
    "skipLibCheck": true,
    "preserveConstEnums": true,
    "incremental": true,
    "composite": true,
    // Output options
    "pretty": true,
    "preserveWatchOutput": true,
    "noErrorTruncation": false
  }
}

Relevant bits of package.json for importing package

{
  "name": "@vanta/some-app",
  "main": "index.js",
  "exports": {},
  "imports": {
    "#some-app/*.json": {
      "node": "./dist/*.json",
      "default": "./src/*.json"
    },
    "#some-app/*.ts": {
      "types": "./src/*.ts",
      "node": "./dist/*.js",
      "default": "./src/*.ts"
    }
  },
  "dependencies": {
    "@vanta/feature-flags": "workspace:*"
  }
}

Relevant bits of package.json for exporting package

{
  "name": "@vanta/feature-flags",
  "exports": {
    "./dynamic-config": {
      "types": "./dist/dynamic-configuration/api.d.ts",
      "node": "./dist/dynamic-configuration/api.js",
      "default": "./src/dynamic-configuration/api.ts"
    },
    "./dynamic-config/eval": {
      "types": "./dist/dynamic-configuration/eval.d.ts",
      "node": "./dist/dynamic-configuration/eval.js",
      "default": "./src/dynamic-configuration/eval.ts"
    },
    "./dynamic-config/testing": {
      "types": "./dist/dynamic-configuration/testing.testutil.d.ts",
      "node": "./dist/dynamic-configuration/testing.testutil.js",
      "default": "./src/dynamic-configuration/testing.testutil.ts"
    }
  },
  "imports": {
    "#feature-flags/*.json": {
      "node": "./dist/*.json",
      "default": "./src/*.json"
    },
    "#feature-flags/*.ts": {
      "types": "./src/*.ts",
      "node": "./dist/*.js",
      "default": "./src/*.ts"
    }
  }
}

I am trying to make an actual reproduction in this repository and will comment if/when I am able to do so.

Behavior with typescript@5.8

The re-export works.

Behavior with tsgo

Module '"@vanta/feature-flags/dynamic-config/testing"' has no exported member 'stubDynamicConfig'.

Re-exporting a named item instead does resolve correctly, so I am using this as a workaround:

export { stubDynamicConfig } from "#feature-flags/dynamic-configuration/dynamic-config-harness.testutil.ts";