Use Gulp to check if a token exists in a file

If I do this:

var gulp = require('gulp');
var replace = require('gulp-replace');
var rename = require('gulp-rename');

gulp.task('TaskExample', function ReplaceExampleFileTokens() {

    return gulp.src('./src/' + 'ExampleFileTokens.config')

        .pipe(replace('#{String}#', 'Hello World'))
        .pipe(rename('ExampleFile.config'))
        .pipe(gulp.dest('./dest'));
    });

I will:

1. replace the token in ExampleFileTokens.config then

2. rename it to ExampleFile.config and

3. finally deposit it in './dest'.

My questions are the following:

• How would you check that #{String}# exists in ExampleFileTokens.config without using gulp.dest if the token doesn't exist?

• I know I could search the file in javascript with the token, but is there a way with maybe gulp-replace, since it's already searching and replacing my tokens?

I don't think there is a way to have gulp-replace do all the work you want. It is troublesome to set a conditional within a stream.

You can do it easily enough with a filter though (gulp-filter.

const gulp = require('gulp');
const replace = require('gulp-replace');
const rename = require('gulp-rename');

const filter = require('gulp-filter');
const filterEach = require('gulp-filter-each')

gulp.task("TaskExample", function () {

  // return true if want the file in the stream
  // const configFilter = filter(function (file) {       
  //   let contents = file.contents.toString();
  //   return contents.match('#{String}#');
  // });

  return gulp.src('./src/' + 'ExampleFileTokens.config')

    // you can use either of the following two filters
    // .pipe(configFilter)
    .pipe(filterEach(content => content.match('#{String}#')))

    .pipe(replace('#{String}#', 'Hello World'))
    .pipe(rename('ExampleFile.config'))
    .pipe(gulp.dest('./dest'));
});