bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Luca Cartasegna]

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Hello,

breaking lines in variables declaration seems to break the color
syntax.

cat main.f90:
program main
integer :: a, &
     b
end program main

The variable a is correctly colored while the variable b is
not(using continuation lines in other parts of the program, not in the
variable declaration, seems to work fine).

Cheers!

Luca




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bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Lars Ingebrigtsen]

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Luca Cartasegna <cartasegna.luca@gmail.com> writes:

> breaking lines in variables declaration seems to break the color
> syntax.
>
> cat main.f90:
> program main
> integer :: a, &
>      b
> end program main
>
> The variable a is correctly colored while the variable b is
> not(using continuation lines in other parts of the program, not in the
> variable declaration, seems to work fine).

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

I've now fixed this in Emacs 29:


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-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Mattias Engdegård]

> I've now fixed this in Emacs 29: 

Thank you for doing this. Relint complained about this part:

-\\(.*::\\|[ \t]*(.*)\\)?\\([^&!\n]*\\)"
-      (1 font-lock-type-face t) (4 font-lock-variable-name-face t))
+\\(.*::\\|[ \t]*(.*)\\)?\\(\\(?:[^&!\n]*\\(?:&\n\\)?\\)+\\)"
+      (1 font-lock-type-face t) (4 font-lock-variable-name-face append))

More specifically, the

\\(?:[^&!\n]*\\(?:&\n\\)?\\)+

part at the end is a potential empty-string repetition that indicates an ambiguity which we'd like to remove.
What is the desired grammar here? Moving to rx for clarity, the above snippet means

(+ (* (not (in "\n!&")))
  (? "&\n"))

What about rewriting it as

(: (* (not (in "\n!&")))
  (* "&\n"
     (* (not (in "\n!&")))))

which should be equivalent but unambiguous?

However there may be something more fundamentally wrong with the original change, because it only seems to work for me after loading a file, not when writing the code incrementally. More precisely, when I've typed

program main
 integer :: alpha, &&

in a new buffer then everything looks correctly coloured, but if I add

  beta

to the next line then it isn't fontified at all. Saving and reloading the buffer helps. Can you confirm?

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Lars Ingebrigtsen]

Mattias Engdegård <mattiase@acm.org> writes:

> part at the end is a potential empty-string repetition that indicates an ambiguity which we'd like to remove.
> What is the desired grammar here? Moving to rx for clarity, the above snippet means
>
> (+ (* (not (in "\n!&")))
>   (? "&\n"))
>
> What about rewriting it as
>
> (: (* (not (in "\n!&")))
>   (* "&\n"
>      (* (not (in "\n!&")))))
>
> which should be equivalent but unambiguous?

Yes, I think that's correct.

> However there may be something more fundamentally wrong with the original change, because it only seems to work for me after loading a file, not when writing the code incrementally. More precisely, when I've typed
>
> program main
>  integer :: alpha, &&
>
> in a new buffer then everything looks correctly coloured, but if I add
>
>   beta
>
> to the next line then it isn't fontified at all. Saving and reloading the buffer helps. Can you confirm?

Yes.  I had forgotten all about the rules for multiline font locking
(i.e., (elisp)Multiline Font Lock).  So I think my changes here were
basically misguided, and this should be implemented in a totally
different way.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Mattias Engdegård]

17 maj 2022 kl. 19.32 skrev Lars Ingebrigtsen <larsi@gnus.org>:

> Yes.  I had forgotten all about the rules for multiline font locking
> (i.e., (elisp)Multiline Font Lock).  So I think my changes here were
> basically misguided, and this should be implemented in a totally
> different way.

Perhaps this bug should be reopened then since it's not really been satisfactorily resolved, and revert the change?

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Lars Ingebrigtsen]

Mattias Engdegård <mattiase@acm.org> writes:

>> Yes.  I had forgotten all about the rules for multiline font locking
>> (i.e., (elisp)Multiline Font Lock).  So I think my changes here were
>> basically misguided, and this should be implemented in a totally
>> different way.
>
> Perhaps this bug should be reopened then since it's not really been
> satisfactorily resolved, and revert the change?

Now reopened.  I'm not sure about reverting -- the patch doesn't make
things worse.  It just doesn't do it right, either.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Mattias Engdegård]

24 maj 2022 kl. 18.03 skrev Lars Ingebrigtsen <larsi@gnus.org>:

> Now reopened.  I'm not sure about reverting -- the patch doesn't make
> things worse.  It just doesn't do it right, either.

That's fine. I pushed the regexp disambiguating suggestion mentioned earlier; hope it's all right.

bug#17222: 24.3; In f90-mode variables declared in continuation lines are not colored.

[Lars Ingebrigtsen]

Mattias Engdegård <mattiase@acm.org> writes:

> That's fine. I pushed the regexp disambiguating suggestion mentioned
> earlier; hope it's all right.

Sure; looks good.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no