How do I make Dartfmt "friendly" for Matrices? - dart

Question

For a Matrix that supposed to look like this:
const ColorFilter sepia = ColorFilter.matrix(<double>[
0.393, 0.769, 0.189, 0, 0,
0.349, 0.686, 0.168, 0, 0,
0.272, 0.534, 0.131, 0, 0,
0, 0, 0, 1, 0,
]);
But dartfmt changed it to become like this:
const ColorFilter sepia = ColorFilter.matrix(<double>[
0.393,
0.769,
0.189,
0,
0,
0.349,
0.686,
0.168,
0,
0,
0.272,
0.534,
0.131,
0,
0,
0,
0,
0,
1,
0,
]);
This is hard to read. Thus, how can I keep the original format so that the Matrix can be seen more "friendly". Or at least how can I make Dartfmt not to reformat any List?

Answer 1

This scenario is described in the FAQ of dart_style which dartfmt is based on:
https://github.com/dart-lang/dart_style/wiki/FAQ#why-does-the-formatter-mess-up-my-collection-literals
In short, you just need to add a comment somewhere in you matrix definition like:
const ColorFilter sepia = ColorFilter.matrix(<double>[
0.393, 0.769, 0.189, 0, 0, //
0.349, 0.686, 0.168, 0, 0,
0.272, 0.534, 0.131, 0, 0,
0, 0, 0, 1, 0,
]);
Then dartfmt will not try to format the newlines in the matrix. It will however, still fixes non-needed spaces so it will make your example into:
const ColorFilter sepia = ColorFilter.matrix(<double>[
0.393, 0.769, 0.189, 0, 0, //
0.349, 0.686, 0.168, 0, 0,
0.272, 0.534, 0.131, 0, 0,
0, 0, 0, 1, 0,
]);
Which can be fixed by changing the 0 to 0.000:
const ColorFilter sepia = ColorFilter.matrix(<double>[
0.393, 0.769, 0.189, 0, 0, //
0.349, 0.686, 0.168, 0, 0,
0.272, 0.534, 0.131, 0, 0,
0.000, 0.000, 0.000, 1, 0,
]);

Answer 2

Whereas #julemand101's answer should be the accepted one, as it directly changes dartfmt's behavior, this spread operator workaround could be worth to mention :
final matrix = [
...[1, 2, 3],
...[4, 5, 6],
...[7, 8, 9],
];