gulp-typescript: tsProject.src() throws errors (gulp.src() doesn't) when using tsconfig.json without "exclude node_modules" section

Expected behavior:

I expected tsProject.src() and gulp.src() to compile .ts files without throwing a bunch of syntax errors from node_modules when using tsconfig.json without adding “exclude node_modules” section in tsconfig.json.

Actual behavior:

tsProject.src() throws a bunch of syntax errors from node_modules (i.e., .d.ts error TS1005: ‘=’ expected, ‘;’ expected). However, gulp.src() works fine. The only way to get tsProject.src() to work is to add “exclude node_modules” section to tsconfig.json. I can leave it out when using gulp.src(). Why is that?

Your gulpfile:

var tsProject = ts.createProject('tsconfig.json');

gulp.task('script', function () {
    var tsResult = tsProject // tsProject throws errors, but gulp doesn't 
        .src(['wwwroot/app/**/*.ts', 'typings/index.d.ts'])
        .pipe(ts(tsProject));

    return tsResult
        .js
        .pipe(gulp.dest('release'));
});

tsconfig.json

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  }
}

Note: I have to add the following in tsconfig.json when using tsProject.src(), but I can leave it out when using gulp.src()

,
  "exclude": [
    "node_modules"
  ]

Question

• Why does tsProject.src() throw errors (while gulp.src() doesn’t) when “exclude” isn’t added to tsconfig.json?
• What is the difference between using tsProject.src() and gulp.src() for tsconfig.json?
• Why does the Using tsconfig.json section suggest using tsProject.src() instead of gulp.src()?

gulp.task('scripts', function() {
    var tsResult = tsProject.src() // instead of gulp.src(...) 
        .pipe(ts(tsProject));

    return tsResult.js.pipe(gulp.dest('release'));
});