OpenSCAD User Manual/WIP/Migration Guide

OpenSCAD 2019 contains changes that break some old design and/or create errors and warnings for code that previously did not.

Variables

Duplicate assignment warning

In the following cases OpenSCAD 2019 creates a warning in case of a duplicate assignment:

• variable overwritten in the same file and scope
• assignment from the mainFile overwritten by an include

In the following cases, the variable is silently overwritten by the last assignment:

• assignment via command line
• variable of an include over written by the main file

uninitialized special variables

This code now causes a warning, as $test is not initialized:

test = $test==undef ? 1 : $test ;

The workaround is the new is_undef() function:

test = is_undef($test) ? 1 : $test ;

Module and function arguments

argument types

Built in functions and modules now warn, when the argument type does not match.

As type checking previously was done by using the built in functions returning undef, it is now recommended/required to use is_list(), is_num(), is_bool() and is_string() for type checking.

duplicate arguments

OpenSCAD 2019 warns, when a named argument is supplied more then once.

cube(size=2,size=1);

not specified arguments

OpenSCAD now warns, when a module or function parameter is not declared.

user modules

Meaning, this now causes a warning:

a=1;

module test(){
    cube(a);
}

test();

translate([2,0,0])
test(a=2);

If doing that is your intention - like in the Write.scad library - you can update the code as follows:

a=1;

module test(a){
    cube(a);
}

test();

translate([2,0,0])
test(a=2);

For Write.scad specifically: Definitions like

module writecircle(text,where,radius){

need to change to

module writecircle(text, where, radius, rotate, font, h, t, spac, east, west, middle, ccw){
</syntaxhighlight lang="unknown">
==== builtin modules ====
Same goes for builtin modules, so this now creates a warning:
<syntaxhighlight lang="text">
sphere(center=true);

and

circle(center=true);

Neither circle nor sphere support the center argument - center and circle are always centered.

An other example is

circle(radius=5);

as circle excepts r, not radius.

arguments overwritten by literal

module test(a){
    a=2;
    sphere(a);
}

test();

translate([4,0,0])
test(a=1);

Note that this very similar example does not trigger a warning, due to quirks in the implementation:

module test(a){
    a=1+1;
    sphere(a);
}

test();

translate([4,0,0])
test(a=2);

arguments range check for builtin modules

things like

cube(-1);
cube([1,1,-1]);
cube(0);
cube([1,1,0]);

argument conflict check for builtin modules

cylinder(h = 1, r1 = 0, r2 = 1, d = 2, center = true);

argument count for builtin functions

If the argument count for builtin functions does not match, OpenSCAD 2019 displays a warning:

echo(abs(123,456));

assert()

The builtin Assert can not be overwritten by a user function or module. If you have a function or module named as assert, you must rename it.