Bug Report

project references transitive dependency stale

🕗 Version & Regression Information

• This changed between versions 3.6.0-dev.20190621 (good) and 3.6.0-dev.20190622 (bad) The incorrect behavior was observed in many versions since then, including:
  • 4.4.2
  • 4.4.3
  • 4.5.0-dev.20210928

⏯ Playground Link

Reproducing the problem requires transitive project references, and running tsc -b from the command line, so I don’t believe it can be done in the TypeScript playground.

💻 Code

My team observed that tsc -b can incorrectly succeed when a problem is introduced by a transitive dependency. In fact, tsc -b can give two different results (type check passes or type check fails) for the same codebase. We created a self-contained reproducible example to demonstrate the problem. This creates 3 projects using project references, where project A depends on project B and that, in turn, depends on project C. There is one TypeScript file in project A, none in B and one in C.

Step 1: Create the following 5 files, distributed into directories projectA/, projectB/ and projectC/.

// projectA/A.ts
import C from '../projectC/C';

class A extends C {
  constructor() {
    super( {} );
    this.name.arbitraryFakeMethod();
  }
}

// projectA/tsconfig.json
{
  "references": [
    {
      "path": "../projectB"
    }
  ],
  "compilerOptions": {
    "module": "commonjs",
    "target": "es5",
    "composite": true,
    "outDir": "./dist/",
    "incremental": true,
    "allowJs": true
  },
  "include": [
    "A.ts"
  ]
}

// projectB/tsconfig.json
{
  "references": [
    {
      "path": "../projectC"
    }
  ],
  "compilerOptions": {
    "module": "commonjs",
    "target": "es5",
    "composite": true,
    "allowJs": true,
    "outDir": "./dist/",
    "incremental": true
  }
}

// projectC/C.ts
class C {
  name: string;
  constructor( options ) {
  }
}

export default C;

// projectC/tsconfig.json
{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es5",
    "composite": true,
    "allowJs": true,
    "outDir": "./dist/",
    "incremental": true
  },
  "include": [
    "C.ts"
  ]
}

Step 2: clean and build project A

The clean step is not necessary on your first run, but we include it here in case you want to run through the steps again.

cd projectA
tsc -b --clean
tsc -b

In this case, the expected result is the same as the actual result, which is a build failure with this message:

A.ts:7:15 - error TS2339: Property 'arbitraryFakeMethod' does not exist on type 'string'.

7     this.name.arbitraryFakeMethod();
                ~~~~~~~~~~~~~~~~~~~


Found 1 error.

Step 3: Fix the error by updating C.ts.

In C.ts, change name: string; to name: any;

Step 4: build project A

tsc -b

Again, the expected result matches the actual result. tsc succeeds with no output.

Step 5. Reintroduce the problem in C.ts

In C.ts, change name: any; back to name: string;

Step 6. Build Project A

tsc -b

🙁 Actual behavior

There is no output from tsc because the type check and build passes successfully. This is incorrect because there is a type error because string does not have a method arbitraryFakeMethod. Note that Step 6 is building the same code as in Step 2. However, in Step 2, the type error is correctly identified, but in Step 6 the type error is missed.

🙂 Expected behavior

Step 6 should produce the following error (as it correctly did in Step 2):

A.ts:7:15 - error TS2339: Property 'arbitraryFakeMethod' does not exist on type 'string'.

7     this.name.arbitraryFakeMethod();
                ~~~~~~~~~~~~~~~~~~~


Found 1 error.

Note that changing project A to depend on C directly (not through B) correctly identifies the problem when running tsc -b in project A, so this bug does require the intermediate transitive dependency. TypeScript correctly caught this error through Version 3.6.0-dev.20190621 (good), but started missing it in 3.6.0-dev.20190622 (bad). For completeness, we will mention that we first detected the problem when projectC was *.js code, so it seems to affect both *.ts and *.js dependencies. This problem was discovered in https://github.com/phetsims/chipper/issues/1067