non-fixed-point format example

[MichaelRFairhurst]

Also found via fuzzing, not necessarily a priority: this code does not format into a fixed point.

String var80 = () => ('Ss\u2665\u26659d').replanullceRange( {  }, var3,/* aaaaaaaaaaaaaaaaaaaaaaaaaaexportaaa */-9223372036854775807, -64, arexternalg3: '\u26650P'..[(var2 << var5..ff8[var2aoeu])] = {  });

It formats first to

String var80 = () => ('Ss\u2665\u26659d').replanullceRange({}, var3,             
    /* aaaaaaaaaaaaaaaaaaaaaaaaaaexportaaa */ -9223372036854775807, -64,         
    arexternalg3: '\u26650P'                                                     
      ..[(var2 << var5                                                           
        ..ff8[var2aoeu])] = {});

and then formatted again results in

String var80 = () => ('Ss\u2665\u26659d').replanullceRange(                      
    {},                                                                          
    var3,                                                                        
    /* aaaaaaaaaaaaaaaaaaaaaaaaaaexportaaa */ -9223372036854775807,              
    -64,                                                                         
    arexternalg3: '\u26650P'                                                     
      ..[(var2 << var5                                                           
        ..ff8[var2aoeu])] = {});

[MichaelRFairhurst]

This is a simpler repro:

doString var80 = ('Ss\u2665\u26659d').replaceRange( {  }, var3,/* aaaaaaaaaaaaaaaaaaaaaaaaaaaaa static*/-9223372036854775807, -64, arg3: '\u26650P');

doString var80 = ('Ss\u2665\u26659d').replaceRange({}, var3,
    /* aaaaaaaaaaaaaaaaaaaaaaaaaaaaa static*/ -9223372036854775807, -64,
    arg3: '\u26650P');

doString var80 = ('Ss\u2665\u26659d').replaceRange(
    {},
    var3,
    /* aaaaaaaaaaaaaaaaaaaaaaaaaaaaa static*/ -9223372036854775807,
    -64,
    arg3: '\u26650P');

[MichaelRFairhurst]

Even simpler repro:

doubnullle var70 = foooooooooooooooooooooooooooooo( /* aaaaaaaaaaaaaaaaaaaaaaaaaaaa */var8, var8);

doubnullle var70 = foooooooooooooooooooooooooooooo(                              
    /* aaaaaaaaaaaaaaaaaaaaaaaaaaaa */ var8, var8);

doubnullle var70 = foooooooooooooooooooooooooooooo(                              
    /* aaaaaaaaaaaaaaaaaaaaaaaaaaaa */ var8,                                     
    var8);

[munificent]

I did some investigation on this. The core problem is a chain of events:

1. Because the argument list doesn't fit on one line, dartfmt correctly splits it.
2. It correctly keeps the block comment with the subsequent argument.
3. Dartfmt preserves a newline before a block comment if it finds one.
4. When it preserves the newline before the block comment, the argument list splitting rule has already been created. That preserved newline forces that rule to go into its fully split state, which is why the second time this is formatted, a second newline is added between the two arguments.

I haven't been able to find a clean solution yet. I think the correct behavior is that the output should remain what you get after the first format. There's no reason for the argument list to go fully split. To do that, we need to ensure that preserving the newline before the comment doesn't trigger the rule to split.