OpenSCAD 2019 contains changes that break some old design and/or create errors and warnings for code that previously did not. 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 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 ; 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. OpenSCAD 2019 warns, when a named argument is supplied more then once. cube(size=2,size=1); OpenSCAD now warns, when a module or function parameter is not declared. 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){  ==== builtin modules ==== Same goes for builtin modules, so this now creates a warning:  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. 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); things like cube(-1); cube([1,1,-1]); cube(0); cube([1,1,0]); cylinder(h = 1, r1 = 0, r2 = 1, d = 2, center = true); If the argument count for builtin functions does not match, OpenSCAD 2019 displays a warning: echo(abs(123,456)); 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.
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