Processing: Tweak mode together with switch() causes error

[jdslab]

Description

Running sketch in tweak mode with the switch() statement somewhere in code causes this error: "case expressions must be constant expressions". Running normally (without tweak mode) works without problems.

Steps to Reproduce

1. run the following code in tweak mode:

void setup() {
  size(200, 200);
}

void draw() {
  background(255);
  int i = 2;
  switch(i){
    case 1: circle(100, 100, 20);
            break;
    case 2: rect(100, 100, 20, 20);
            break;
  }
}

Your Environment

• Processing version: 3.5.4
• Operating System and OS version: tested on macOS 10.15.4 and Windows 10 Version 1909
• Other information:

[jeremydouglass]

Are any sketches working in Tweak mode for you?

[galsasson]

The issue here is Tweak mode trying to convert case 1: into case <variable>: so it breaks the case statement.
A fix should be added to https://github.com/processing/processing/blob/master/java/src/processing/mode/java/tweak/SketchParser.java to ignore case statements.

Meanwhile, as a workaround, you can enable tweaking only specific lines by adding the comment:
/// tweak
at the end of each line you wish to tweak. When adding such comment, Tweak mode will ignore the rest of the values in the sketch.

[jeremydouglass]

Seems like that might be handled as a special case in SketchParser.addAllDecimalNumbers()

[jeremydouglass]

Meanwhile, as a workaround, you can enable tweaking only specific lines by adding the comment:
/// tweak

I can confirm that the workaround works. (It requires that you separate the case statement from its first line.)

void setup() {
  size(200, 200);
}

void draw() {
  background(255); /// tweak
  int i = 2;
  switch(i) {
  case 1:
    circle(100, 100, 20); /// tweak
    break;
  case 2:
    rect(100, 100, 20, 20); /// tweak
    break;
  }
}