TS 5.6 `files` missing from `--showConfig` (with absolute / ``${configDir}`` `include` paths)

[stabpd]

🔎 Search Terms

"--showConfig", "include", "configDir", "files", "extends", "absolute"

🕗 Version & Regression Information

• Tested versions:
  • 3.2.1 (--showConfig was introduced here)
  • 3.2.4
  • 5.5.2 (${configDir} was introduced here)
  • latest => 5.6.3
  • next =>5.7.0-dev.20241011
• This is the behaviour in every version I tried, and I reviewed the FAQ for entries about "configDir", "showConfig", "absolute".
• I was unable to test this on prior versions because --showConfig cli flag was introduced in TS 3.2 and configDir template variable was introduced in TS 5.5.

⏯ Playground Link

No response

💻 Code

// tsconfig-rel.json
{
    //...
    "include": ["src/**/*"]
}

// tsconfig-abs.json
{
    //...
    "include": ["/path/to/src/**/*"]
}

// tsconfig-cnf.json
{
    //...
    "include": ["${configDir}/src/**/*"]
}

// src/index.ts
console.log("dummy");

🙁 Actual behavior

❌ Printing config yields different results.

npx tsc --project tsconfig-rel.json --showConfig
npx tsc --project tsconfig-abs.json --showConfig
npx tsc --project tsconfig-cnf.json --showConfig

• For absolute include paths the files property is missing.
• ${configDir} is resolved to and behaves / fails the same as absolute paths.

  {
      "compilerOptions": {...},
-     "files": [
-         "./src/index.ts"
-     ],
      "include": [
-         "src/**/*"
+         "/path/to/src/**/*"
      ],
      "exclude": [...]
  }

✅ Listing files yields the same output.

npx tsc --project tsconfig-rel.json --listFiles --noEmit
npx tsc --project tsconfig-abs.json --listFiles --noEmit
npx tsc --project tsconfig-cnf.json --listFiles --noEmit

List of files printed to stdout, containing

• /path/to/src/index.ts
• /path/to/`node_modules//*.d.ts`** entries from npm dependency type declarations.
• /path/to/node_modules/typescript/lib/lib.decorators.d.ts (only in TS 5 of course)
• /path/to/node_modules/typescript/lib/lib.decorators.legacy.d.ts (only in TS 5 of course)

✅ Building yields the same index.js file content for all configs.

npx tsc --project tsconfig-rel.json
npx tsc --project tsconfig-abs.json
npx tsc --project tsconfig-cnf.json

🙂 Expected behavior

--showConfig should show the same files for configs that build the same files and show the same listing for --listFiles.

Additional information about the issue

includeRe in matchesSpecs seems to be calculated differently for absolute / relative paths, resulting in all files being filtered out in convertToTSConfig.

I can't tell though which behaviour is actually expected. (keep files or filter files out?)

[RyanCavanaugh]

I don't know if anyone is really putting absolute paths in their config files; this seems like a nonstandard usage. showConfig is intended for human consumption so it's not really wrong for it to do different things given different inputs. Not sure what the "best" behavior is but if someone really needs to change it to some provably better outcome, they can.

[stabpd]

I agree that this is not an urgent matter. Let me add a little clarification for future discussion though:

For me, it's not about manually configured absolute paths, but about ${configDir} which has the same issue, because the template variable gets substituted with absolute paths internally.

When switching from a monolithic config to a base tsconfig.json that I could extend, I wanted to verify changes via showConfig. Seeing no files there, no matter what I did, almost made me discard using that nice new ${configDir} feature.

I can live with the current behaviour, now that I know. But maybe this will confuse other users as well, leading them down the wrong path too.