SDF pretty-printer is not sound, i.e. it is possible to construct a language for which a valid program p exists such that pretty-print(parse(p)) is no longer a valid program.

Steps to reproduce:

1. build metaborg-sl in Spoofax 2.4.0-SNAPSHOT (currently: 20171026-103626) using the Java parse table generator (sdf2tabe: java)
2. open the following program in foo.sl, notice that it parses successfully:

   function p(a) {
     (1 < (true / false || m)).x = 1; 
   }
   

3. hit Syntax > Format and observe the pretty-printed program:

   function p(a) {
     1 < true / false || m.x = 1;
   }
   

4. observe the little red box saying “Internal parsing error”.

It looks like the logic that adds parenthesis does not work for this grammar (admittedly; the grammar is kinda weird). I’m not sure if this is intended, so I thought I’d create an issue.

Also, unrelated to the pretty-printer, I’m surprised that the parse fails. Looking at the grammar I can construct a tree that could be the result of the parse, but right now the parse just fails with “Internal parsing error: org.spoofax.jsglr.client.FilterException: Runtime exception when applying filters (recovery failed)”..

Submitted by Martijn on 13 November 2017 at 12:37

Also, unrelated to the pretty-printer, I’m surprised that the parse fails. Looking at the grammar I can construct a tree that could be the result of the parse, but right now the parse just fails with “Internal parsing error: org.spoofax.jsglr.client.FilterException: Runtime exception when applying filters (recovery failed)”.

(I tried editing my original issue and adding above message, but upon saving the edit disappears. Should I create a meta-issue for this?)