Autocomplete incorrectly suggests transitive files from monorepo package

[ericnorris]

Extension Version

0.20260124.1

VS Code Version

1.108.2

Operating system Version

macOS 15.7

Steps to reproduce

I've written a failing fourslash test to demonstrate the issue:

package fourslash_test

import (
	"testing"

	"github.com/microsoft/typescript-go/internal/fourslash"
	. "github.com/microsoft/typescript-go/internal/fourslash/tests/util"
	"github.com/microsoft/typescript-go/internal/ls"
	"github.com/microsoft/typescript-go/internal/lsp/lsproto"
	"github.com/microsoft/typescript-go/internal/testutil"
)

const TestAutoImportTransitiveLeakScenario = `
// @Filename: /home/src/workspaces/project/tsconfig.base.json
{
  "compilerOptions": {
    "module": "nodenext",
    "moduleResolution": "nodenext",
    "composite": true
  }
}

// @Filename: /home/src/workspaces/project/packages/foo/package.json
{
  "name": "@packages/foo",
  "type": "module",
  "exports": {
    ".": {
	  "types": "./src/index.ts",
	  "default": "./dist/index.js"
	}
  },
  "imports": {
    "#*": {
	  "types": "./src/*.ts",
      "default": "./dist/*.js"
    }
  }
}

// @Filename: /home/src/workspaces/project/packages/foo/tsconfig.json
{ "extends": "../../tsconfig.base.json" }

// @Filename: /home/src/workspaces/project/packages/foo/src/internal/index.ts
export function fooInternal() {
  console.log("foo");
}

// @Filename: /home/src/workspaces/project/packages/foo/src/index.ts
import { fooInternal } from "#internal/index"
export function foo() {
  fooInternal();
}

// @Filename: /home/src/workspaces/project/packages/bar/package.json
{
  "name": "@packages/bar",
  "type": "module",
  "exports": {
    ".": {
	  "types": "./src/index.ts",
	  "default": "./dist/index.js"
	}
  },
  "imports": {
    "#*": {
	  "types": "./src/*.ts",
      "default": "./dist/*.js"
    }
  },
  "dependencies": {
    "@packages/foo": "*"
  }
}

// @Filename: /home/src/workspaces/project/packages/bar/tsconfig.json
{ "extends": "../../tsconfig.base.json" }

// @Filename: /home/src/workspaces/project/packages/bar/src/index.ts
import { foo } from "@packages/foo"

fo/*fooCompletion*/

// @Filename: /home/src/workspaces/project/package.json
{ "workspaces": ["packages/*"], "type": "module" }

// @link: /home/src/workspaces/project/packages/bar -> /home/src/workspaces/project/node_modules/@packages/bar
// @link: /home/src/workspaces/project/packages/foo -> /home/src/workspaces/project/node_modules/@packages/foo
`

func TestAutoImportTransitiveLeak(t *testing.T) {
	t.Parallel()

	defer testutil.RecoverAndFail(t, "Panic on fourslash test")

	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, TestAutoImportTransitiveLeakScenario)

	defer done()

	f.VerifyCompletions(t, "fooCompletion", &fourslash.CompletionsExpectedList{
		IsIncomplete: false,
		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
			CommitCharacters: &DefaultCommitCharacters,
			EditRange:        Ignored,
		},
		Items: &fourslash.CompletionsExpectedItems{
			Includes: []fourslash.CompletionsExpectedItem{
				&lsproto.CompletionItem{
					Label:               "foo",
					AdditionalTextEdits: fourslash.AnyTextEdits,
					SortText: PtrTo(string(ls.SortTextLocationPriority)),
				},
			},
			Excludes: []string{"fooInternal"},
		},
	})
}

I placed it at internal/fourslash/tests/autoImportTransitiveLeak_test.go.

Issue

Similar to microsoft/TypeScript#63033, but I've reproduced it here. I don't believe that it should suggest fooInternal as an autocomplete, as it's not actually exported. What does happen, however, is that it suggests fooInternal, and accepting it produces the following code with a red squiggly line on the second import:

import { foo } from "@packages/foo";
import { fooInternal } from "@packages/foo/src/internal/index.js";

fooInternal

The diagnostic then says Cannot find module '@packages/foo/src/internal/index.js' or its corresponding type declarations.

Additional information about the issue

This was very difficult for me to reproduce, but I believe I've identified two variables that prevent the bug from surfacing:

• Add a version field to the packages/foo/package.json, or
• Add "preserveSymlinks": true to tsconfig.base.json