Declaration files not generated with inherited tsconfig.json

[yahiko00]

When the tsconfig.json directly used by the TypeScript project does not explicitly set declaration to true, even if its parent does, then gulp-typescript does not generate declaration files, unlike the inline compiler tsc.

I use gulp-typescript version 3.1.7 and TypeScript 2.4.1.

Here is the gulpfile.js:

const tsProject = ts.createProject(config);
const tsResult = tsProject.src()
    .pipe(sourcemaps.init())
    .pipe(tsProject());

return merge([
    tsResult.js
        .pipe(sourcemaps.write())
        .pipe(gulp.dest(dest)),
    tsResult.dts
        .pipe(rename("index.d.ts"))
        .pipe(gulp.dest(dest))])
    .on("error", gutil.log);

Above, the parameter config in the createProject() method refers to the following tsconfig.debug.json:

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

Here is its parent, tsconfig.json:

{
  "include": [ "./src/**/*.ts" ],
  "compilerOptions": {
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */

    "declaration": true,                      /* Generates corresponding '.d.ts' file. */

    "removeComments": true,                   /* Do not emit comments to output. */
    "strict": true,                           /* Enable all strict type-checking options. */
    "noUnusedLocals": true,                   /* Report errors on unused locals. */
    "noUnusedParameters": true,               /* Report errors on unused parameters. */
    "noImplicitReturns": true,                /* Report error when not all code paths in function return a value. */
    "noFallthroughCasesInSwitch": true        /* Report errors for fallthrough cases in switch statement. */
  }
}

To solve this issue, we need to explicitely set declaration to true in the createProject() method, or repeat "declaration": true in the inherited tsconfig.json (here, tsconfig.debug.json).

This issue refers to this one: #231

[ivogabe]

Duplicate of #459, will be part of a new release soon