fail: incorrect conditional logic as else blocks move to new location

[Troid92]

Input:

float getNum(float a) {
  if (a > 0.0) {
    if (a > 1.0) return 1.0;
  }
  else return 0.0;
  return a;
}

In the above, getNum(0.5) returns 0.5 and getNum(-1.0) returns 0.

Shader_Minifier output (text format):

float f(float f){if(f>0.)if(f>1.)return 1.;else return 0.;return f;}

In the above, f(0.5) returns 0. and f(-1.0) returns -1.0

Expected output:

float f(float f){if(f>0.){if(f>1.)return 1.;}else return 0.;return f;}

In the above, f(0.5) returns 0.5 and f(-1.0) returns 0.

While this example can be simplified to clamp(a,0.,1.), I did experience this bug in a situation where the logic could not be simplified.

Workarounds:
The best workaround I could find is to use an older version of Shader_Minifier as this is technically a regression.
Otherwise I am not aware of any catch-all solution. In the above example, the conditional logic could be flipped (start with if (a <= 0.0) return 0.0; else ...) which would produce the correct result. However, if the current else statement had similarly nested ifs then flipping the branches would no longer work. Adding an empty else {} in the inner block will not work as it will be removed by Shader_Minifier.

[laurentlb]

Thanks for the nice report!

This seems to be a corner-case where removing the curly braces isn't safe. I suppose we could preserve the curly braces when the inner block is a if.

I'm surprised older versions of the Minifier didn't have this bug. We'll need to investigate and see what happened.