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Concatenation of Files

For example, we have the following TypeScript-files: a.ts, b.ts, c.ts, d.ts. We compile its (b and c compile to a single file):

tsc --sourceMap a.ts
tsc --sourceMap --out bc.js b.ts c.ts
tsc --sourceMap d.ts

As a result, we have JavaScript sources a.js, bc.js and d.js. And source maps a.js.map, bc.js.map, d.js.map.

We want to concatenate all the sources into one file: a.js + bc.js + d.js -> out.js. And we want to create a source map file out.js.map that is referred to TypeScript sources.

Method concat()

concat(SourceMap $map, int $line [, int $column]):void

This method takes a source map and merges it with the current. The positions of the current map remain in its places, and new positions are added to certain places.

The argument $map can be

  • A SourceMap instance
  • An array of a source map data ([...'sources'=>[...],'mappings'=>'...')
  • A string of a file name of a source map

The Algorithm

  • Build the empty file out.js and the empty source map out.js.map.
  • Add the contents of next js-file to the out.js.
  • Calculate the number of lines of js-files and start line of each of these files.
  • Add the next source map to the resulting source map to the calculated line.
$resultMap->concat('d.js.map', 10);

10 is start line of the contents of d.js in out.js.

If we merge the files into a single string, it is necessary remember size of the content instead the lines number. And use the argument $column instead $line.

The example

use axy\sourcemap\SourceMap;

$files = ['a.js', 'bc.js', 'd.js'];
$outFile = 'out.js';
$outMap = $outFile.'.map';

// Create the empty source map
$map = new SourceMap();
$map->file = $outFile;

// The content of the resulting file
$result = [];

$line = 0;
foreach ($files as $name) {
    $jsFile = __DIR__.'/'.$name;
    $mapFile = $jsFile.'.map';
    // load the next file
    $content = file_get_contents($jsFile);
    // remove link to a source map
    $content = preg_replace('~//# sourceMappingURL.*$~s', '', $content);
    $content = rtrim($content);
    $result[] = $content;
    // add next file
    $map->concat($mapFile, $line); 
    // shift to next position    
    $line += substr_count($content, "\n") + 1;    
}

// add a link to the resulting source map
$result[] = '//# sourceMappingURL='.$outMap;

// save the resulting JS-file
$result = implode("\n", $result);
file_put_contents(__DIR__.'/'.$outFile, $result); 

// save the resulting source map
$map->save(__DIR__.'/'.$outMap);

Note

If we call concat() with a SourceMap instance as argument, then it is better not to use this instance in the future.

$map1 = SourceMap::loadFromFile('one.map');
$map2 = SourceMap::loadFromFile('two.map');

$map1->concat($map2, 10);

unset($map2); // this object can be incorrect

If the object is required in the future then clone it.

$map1->concat(clone $map2, 10);