Support for handling long if/else chains

[koppor]

(This is somehow #742)

prettier took 98s to format a 146 line file

jabgui/src/main/java/org/jabref/gui/fieldeditors/FieldEditors.java 98670ms (unchanged)

https://github.com/JabRef/jabref/blob/d06248feabd0003d97c5f5417d345c4aa4af4b2c/jabgui/src/main/java/org/jabref/gui/fieldeditors/FieldEditors.java#L42

At these < 1k LOC files, I gave up after some minutes

• https://github.com/JabRef/jabref/blob/d06248feabd0003d97c5f5417d345c4aa4af4b2c/jablib/src/main/java/org/jabref/logic/importer/fileformat/BiblioscapeImporter.java#L28
• https://github.com/JabRef/jabref/blob/d06248feabd0003d97c5f5417d345c4aa4af4b2c/jablib/src/main/java/org/jabref/logic/importer/fileformat/RisImporter.java#L32

[jtkiesel]

All these files have 1 thing in common that appears to be tripping up our parser: long if/else if chains. I found that our parser is rather slow when dealing with chains with lengths of 15 (~1 second in total), but it gets much worse with lengths >15, and beyond 18, the time to parse appears to double for each additional else if. By 23, the time to parse is close to 1.5 minutes. Here is an example of what I've been using to test this:

class Example {

  void example() {
    if (1) {
    } else if (2) {
    } else if (3) {
    } else if (4) {
    } else if (5) {
    } else if (6) {
    } else if (7) {
    } else if (8) {
    } else if (9) {
    } else if (10) {
    } else if (11) {
    } else if (12) {
    } else if (13) {
    } else if (14) {
    } else if (15) {
    } else if (16) {
    } else if (17) {
    } else if (18) {
    } else if (19) {
    } else if (20) {
    } else if (21) {
    } else if (22) {
    } else if (23) {
    }
  }
}

I'm not sure reporting progress is the answer (and I'm not quite sure how to approach that anyway), as parsing/formatting should never be taking this long to begin with -- it's meant to be possible to perform these actions rapidly on file save, etc.

I've been meaning to look into refactoring our parser for awhile now, and perhaps it's time to do so. Will try to do some more investigating.

[Seledrex]

Today I upgraded from 2.6.7 to 2.7.3. After running the formatter, I have run into the same problem with a file in our codebase that has an if / else chain of length 32. I've decided to stick with 2.6.7 for the meantime, and I am hoping this problem will be resolved eventually. Thanks for investigating!

[jtkiesel]

@koppor and @Seledrex: The fix for this is included in prettier-plugin-java 2.7.5! 🎉 Please upgrade and give it a try at your earliest convenience. Thank you for your patience and for using Prettier Java!