I spend all day on this, since some tests I have were failing when I changed to using Physics:-Latex() vs. latex(). I made no change at all in my own code other than to replace latex() by Physics:-Latex().
I am still not sure why that is, but it seems due to symbol clash somewhere. First time I run my test, it passes, next time if fails. When I change back to latex(), the test passes each time.
This seems to be due to when calling Physics:-Latex() the very first time, it automatically changing diff(y(x),x) to y'(x). May be it is storing its own x in there. (this happens on special input and not for each input, that is why only some tests fail and not all of them).
So next time I call the test it failes. May be due to different x being used. I do not know.
All what I know now is that using latex() makes my dsolve test passes each time.
But here I will show the issue which I think if fixed, should fix the main problem.
Calling Physics:-Latex() causes it to automatically change diff(y(x),x) to y'(x) even though I am not using Typeseeting at all.
s:= y = u*x: #special case input which causes the typesetting to kick in
Physics:-Latex(s,output = string):
Notice how the derivative changes on its own to using y'(x). Now compare with latex()
s:= y = u*x:
latex(s,output = string):
So something happens inside Physics:-:Latex which causes this.
For now, I will change back to latex() until I figure more what is going on so that my test do not fail. I like to use Physics:-:Latex as it made the latex look much better.
Maple 2020.1, Physics 778
This change of typesetting does not happen all the time. For example if s:= y = x: then it works OK. i.e. it does not change typesetting. But if s:= y = u*x: then it changes typesetting. which is very strange why that is.
I stepped into Physics:-Latex using the debugger., The typesetting changes after the call to Physics:-Latex:-Print.