nest build silently produces no output with TypeScript 6 + incremental: true

[ReemX]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

nest build exits with code 0 but produces no dist/ directory, no errors, no warnings. The build appears to succeed silently but emits zero files.

The behavior is flaky — sometimes it works (when no .tsbuildinfo exists), sometimes it silently skips emit (when a stale .tsbuildinfo is present). deleteOutDir: true in nest-cli.json makes it worse because it removes dist/ before emit, but the incremental compiler thinks nothing changed.

This affects nest build and nest start --watch (which reports "Found 0 errors" but dist/main.js doesn't exist).

Running tsc --project tsconfig.build.json directly works every time.

Minimum reproduction code

https://gist.github.com/ReemX/c9ad51f31a9abd5ed0d9b8678ddbc832

Steps to reproduce

1. Create a new NestJS project: nest new repro --strict
2. Install TypeScript 6: npm i typescript@6
3. Add "incremental": true to tsconfig.build.json compilerOptions (or inherit it from an extended config)
4. Run npx nest build
5. Check dist/ — it does not exist

Expected behavior

nest build should emit compiled JavaScript files to dist/ (same as tsc -p tsconfig.build.json).

Package version

11.0.17

NestJS version

11.1.17

Node.js version

22.18.0

In which operating systems have you tested?

• Windows
• macOS
• Linux

Other

Root cause: In lib/compiler/compiler.js (line 21), the CLI prefers ts.createIncrementalProgram over ts.createProgram:

const createProgram = tsBinary.createIncrementalProgram || tsBinary.createProgram;

With TypeScript 6, createIncrementalProgram with incremental: true returns a program whose .emit() reports emitSkipped: false and diagnostics: [] but writes zero files to disk. The same call with createProgram works correctly.

Verification script (save as verify.js):

const ts = require('typescript');
const configPath = require('path').join(process.cwd(), 'tsconfig.build.json');
const { options, fileNames, projectReferences } = ts.getParsedCommandLineOfConfigFile(configPath, undefined, ts.sys);

const prog = ts.createIncrementalProgram({ rootNames: fileNames, projectReferences, options });
const result = prog.emit();
console.log('emitSkipped:', result.emitSkipped);   // false
console.log('emittedFiles:', result.emittedFiles);  // [] — empty!
console.log('dist exists:', require('fs').existsSync('dist'));  // false

Workaround: Set "incremental": false in tsconfig.build.json.

This may also warrant a bug report on the TypeScript side (microsoft/TypeScript) since createIncrementalProgram silently succeeding with no output seems like a TS 6 regression.

[kamilmysliwiec]

Would you like to create a PR for this issue?

[ReemX]

Updated Root Cause Analysis

After deeper investigation, the original report was slightly off — createIncrementalProgram itself works correctly in TS 6. The actual bug is a conflict between deleteOutDir and incremental compilation.

The Three-Way Interaction

1. nest-cli.json has deleteOutDir: true → deletes dist/ before every build
2. tsconfig has incremental: true with tsBuildInfoFile pointing outside dist/ (e.g. ./node_modules/.tmp/tsconfig.tsbuildinfo)
3. TypeScript 6 changed createIncrementalProgram behavior: if the .tsbuildinfo says sources haven't changed, it now truly skips emit — reporting emitSkipped: false but writing zero files

Reproduction (deterministic, not flaky)

const ts = require('typescript'); // 6.0.2
const fs = require('fs');
const path = require('path');

const configPath = path.join(process.cwd(), 'tsconfig.build.json');
const parsed = ts.getParsedCommandLineOfConfigFile(configPath, undefined, ts.sys);

for (let i = 1; i <= 3; i++) {
  // Simulate deleteOutDir — removes dist/ but NOT the tsbuildinfo
  fs.rmSync('dist', { recursive: true, force: true });

  const p = ts.createIncrementalProgram({ rootNames: parsed.fileNames, options: parsed.options });
  const r = p.emit();
  console.log(\`Run \${i}: dist/main.js=\${fs.existsSync('dist/main.js')} emitSkipped=\${r.emitSkipped}\`);
}
// Run 1: dist/main.js=true  emitSkipped=false  ← first build works (no tsbuildinfo yet)
// Run 2: dist/main.js=false emitSkipped=false  ← tsbuildinfo exists, TS skips emit
// Run 3: dist/main.js=false emitSkipped=false  ← same

In TypeScript 5, createIncrementalProgram would re-emit even when the tsbuildinfo said nothing changed. TypeScript 6 is stricter and actually skips the emit — but doesn't set emitSkipped: true, making the failure completely silent.

Why It Appears Flaky

• First build after pnpm install: works (no .tsbuildinfo yet → full build)
• Every subsequent nest build: fails (dist/ deleted by deleteOutDir, but .tsbuildinfo survives → TS thinks nothing changed → skips emit)

Fix

In deleteOutDirIfEnabled (lib/compiler/helpers/delete-out-dir.js), also delete the .tsbuildinfo file when deleteOutDir is enabled. This forces createIncrementalProgram to do a full build after cleanup — consistent with the intent of deleteOutDir.

async function deleteOutDirIfEnabled(configuration, appName, dirPath, tsOptions) {
  const isDeleteEnabled = getValueOrDefault(configuration, 'compilerOptions.deleteOutDir', appName);
  if (!isDeleteEnabled) {
    return;
  }
  await rm(dirPath, { recursive: true, force: true });
  // Also clean tsbuildinfo so incremental compiler doesn't skip emit
  if (tsOptions?.tsBuildInfoFile) {
    await rm(tsOptions.tsBuildInfoFile, { force: true });
  }
}

The caller in build.action.js already has tsOptions available and can pass it through.

Workaround

Set "incremental": false in tsconfig.build.json (not tsconfig.json — keep it for typecheck speed):

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "incremental": false
  }
}

Happy to open a PR with the fix if that would be helpful.