Check if file contains a specific string in GULP

Question

I am attempting to use GULP4 to compress a series of HTML and PHP files. A problem I am running into is some of the files contain a <pre> tag. I do not want to compress those files because it would mess up that file. Is there a way using GULP I can evaluate if a file contains the string <pre> and if it does, avoid running compression on that file? Here is my relevant code:

  const gulp = require('gulp');
  const {src, series, parallel, dest} = require('gulp');
  const GulpReplace = require('gulp-replace');
    function no_2_spaces_purchasingdemand_php()
    {
        console.log("no 2 spaces purchasingdemand_php")
        return gulp.src
        (
            'dist/purchasingdemand/**/*.php'
            ,  { base: "./" }
        )
        .pipe
        (
            GulpReplace(' ','☺☻')
        )
        .pipe
        (
            GulpReplace('☻☺','')
        )
        .pipe
        (
            GulpReplace('☺☻',' ')
        )
        .pipe(gulp.dest('./'))
   }
   exports.default = series(no_2_spaces_purchasingdemand_html)

Answer 1

I don't know what you are using to compress files, but here is a general example:

const gulp = require('gulp');
const filter = require('gulp-filter');
const minify = require('gulp-htmlmin');


gulp.task("preFilterTask", function () {
  
  // return true if want the file in the stream
  const preFilter = filter(function (file) {
    let contents = file.contents.toString();
    return !contents.match('<pre>');
  });

  return gulp.src("./*.html")
  
    .pipe(preFilter)
    .pipe(minify({ collapseWhitespace: true }))
    .pipe(gulp.dest('filtered'));
});

  
gulp.task('default', gulp.series('preFilterTask'));

gulp-htmlmin by itself - for html files only - will not minify the <pre>...</pre> portion of an html file. So if you use gulp-htmlmin for html minification, you don't need to filter out those with <pre> tags.

I still showed how to filter based on file content using the gulp-filter plugin. It can access each file's contents. Return false from the filter function if you do not want that file to pass to the next pipe.