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. 

restart;
s:= y = u*x:  #special case input which causes the typesetting to kick in
ode:=diff(y(x),x)=1:
print(ode);
Physics:-Latex(s,output = string):
print(ode);

Notice how the derivative changes on its own to using y'(x).  Now compare with latex()

restart;
s:= y = u*x:
ode:=diff(y(x),x)=1:
print(ode);
latex(s,output = string):
print(ode);

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
 

Additional observation

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.

Download latex_issue_2.mw

I am learning Typesetting so I can get better Latex.

I'd like to have all derivatives generated as y'(x) and not dy/dx regardless of what the derivative variable is. (It is more clear this way).

I found I can't even give Maple a list of the variables. But must do it each time one at a time.

I have thousands of ODE's I need to typeset, (they use different variables (depending on the textbook), and not always x or t, but the set of variables is not large).

so having to check and keep changing this setting each time is awkward (but I think is doable, as I know what the independent variable is for each ode so I can call Typesetting at start of each ode processing, once I know what the variable is).   

It wil be much easier if there is a way to tell Maple to do this for all variables. May be there is a good reason why Maple does not seem to allow such an option?

Here is an example

Typesetting:-Settings(usedot=false,prime=t,typesetprime=true):
ode:=diff(y(t),t$2)+diff(y(t),t)+y(t)= 0:
Physics:-Latex(ode);

Which gives the Latex I want

But if the variable was x instead of t, I have to do this

Typesetting:-Settings(usedot=false,prime=x,typesetprime=true):
ode:=diff(y(x),x$2)+diff(y(x),x)+y(x)= 0:
Physics:-Latex(ode);

I tried doing prime=[x,t] but Maple did not like this.

Is there a way or trick to tell Maple to use typesetprime=true for any letter?  I looked at https://fr.maplesoft.com/support/help/Maple/view.aspx?path=Typesetting%2fSettings but do not see a way so far.

Maple 2020.1 with Physics 776

I am trying the new Physics:-Latex command in version 774.

Couple of isssues I found:

1) One test I have failed with this error

Error, (in anonymous procedure called from anonymous procedure called from anonymous procedure called from anonymous procedure called from Physics:-*) invalid boolean expression: NULL
 

Using the normal latex() command works OK. I hope it is not too hard to fix since this new version seems to have fixed the fraction problem in latex(). Please see

restart;
sol:=dsolve(t*(t-2)^2*diff(diff(y(t),t),t)+t*diff(y(t),t)+y(t) = 0,y(t));
latex(sol);  #OK

Physics:-Latex(sol); #error

2) Maple now generates Latex using maple macro, which I do not know what it is.  Comparing

restart;
ode:=t*(t-2)^2*diff(diff(y(t),t),t)+t*diff(y(t),t)+y(t) = 0;
latex(ode)

which gives 

t \left( t-2 \right) ^{2}{\frac {{\rm d}^{2}}{{\rm d}{t}^{2}}}y
 \left( t \right) +t{\frac {\rm d}{{\rm d}t}}y \left( t \right) +y
 \left( t \right) =0

compare to

Physics:-Latex(ode)

which gives

t \left(t -2\right)^{2} \Mapleoverset{\ldots}{y}\left(t \right)
      +t \Mapleoverset{.}{y}\left(t \right)+y \left(t \right) = 0

What is \Mapleoverset ? googling around, these look like part of internal Maple style sheet for Latex?

Does this mean when using the new Physics Latex command, now one needs to use the package maplestd2e.sty?  With the normal latex() command, this was not needed. 

Just trying to understand the new setup.

why   print(lastexception);  gives `[Length of output exceeds limit of 1000000]` while just doing lastexception; gives no problem?

restart;
eq:=x*y*p = y^2+x*(4*x^2+y^2)^(1/2);
try
   sol:= timelimit(20,`assuming`([solve(eq,y)],[real]));
catch:
   print(lastexception);
end try;
lastexception

I know one should use something like

print(StringTools:-FormatMessage( lastexception ))

But I do not know why print(lastexception) gives the length exceeds error. 

whattype(lastexception) gives exprseq

Maple 2020.1

Just wondering why

restart;
x:=2*{};
has(x,{})

Clearly {} is special. But is there a way to make it return true?