Improve tree shakability

[fisker]

echo export{convertChangesToDMP}from"diff" | npx esbuild --bundle --format=esm

Expect output to only include convertChangesToDMP, instead of 800+ LOC

[fisker]

Sorry I didn't notice that files in libesm/ are exported, I should import from the file directly instead of the index file.

Great work! Thanks!

[ExplodingCabbage]

Yep, I put that feature in specifically to avoid breaking the imports in Prettier that I recalled imported from lib/ (though apparently that got changed in Pretter in the meantime and I hadn't noticed).

I am curious why esbuild can't manage to notice that those 800 lines of extra code are unused and purge them from the output, though! It's not obvious to me that importing directly from diff should give a different result at all.

[fisker]

I put that feature in specifically to avoid breaking the imports in Prettier that I recalled imported from lib/ (though

Thanks! Yes, we imported from lib/ directly before, but changed for some reason I can't remember. prettier/prettier#16397

I am curious why esbuild can't manage to notice that those 800 lines of extra code are unused and purge them from the output

I guess that's because lines like this

jsdiff/src/diff/sentence.ts

Line 10 in a5cf0db

export const sentenceDiff = new SentenceDiff();

were not marked as "pure", can also caused by tansformed classes, I didn't dig, just my guess.

[fisker]

I wonder if put sideEffects: false in package.json will make the extra code go away.

[fisker]

As I tested, sideEffects: false doesn't work.

My guess is correct, if I do

to all the files in libesm/

, I got

>echo export{convertChangesToDMP}from"diff" | npx esbuild --bundle --format=esm
// node_modules/diff/libesm/diff/word.js
var extendedWordChars = "a-zA-Z0-9_\\u{C0}-\\u{FF}\\u{D8}-\\u{F6}\\u{F8}-\\u{2C6}\\u{2C8}-\\u{2D7}\\u{2DE}-\\u{2FF}\\u{1E00}-\\u{1EFF}";
var tokenizeIncludingWhitespace = /* @__PURE__ */ new RegExp("[".concat(extendedWordChars, "]+|\\s+|[^").concat(extendedWordChars, "]"), "ug");

// node_modules/diff/libesm/convert/dmp.js
function convertChangesToDMP(changes) {
  var ret = [];
  var change, operation;
  for (var i = 0; i < changes.length; i++) {
    change = changes[i];
    if (change.added) {
      operation = 1;
    } else if (change.removed) {
      operation = -1;
    } else {
      operation = 0;
    }
    ret.push([operation, change.value]);
  }
  return ret;
}
export {
  convertChangesToDMP
};