[m-rev.] changed "no targets specified" message

[Peter Wang]

On Tue, 22 Nov 2022 23:05:59 +1100 "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> 
> 2022-11-22 17:15 GMT+11:00 "Peter Wang" <novalazy at gmail.com>:
> > How about one of:
> > 
> > mercury_compile: *** Error: no target specified.
> > mercury_compile: *** Error: no target or `MAIN_TARGET' specified.
> > mercury_compile: *** Error: no target specified and `MAIN_TARGET' not defined.
> 
> I am fine with either the second or third, though I don't see the point
> of quoting MAIN_TARGET.

I agree. Patch attached.

> 
> > For other errors, I'd prefer each error message to appear on a single
> > line, even if it might exceed what the compiler *thinks* the window
> > width is. If they happen to be formatted with error_specs then I think
> > they should behave as though --no-max-error-line-width was passed.
> 
> At the moment, there is no way to embed the instruction "ignore the
> max line width" in an error_spec. Adding such a mechanism
> would not be hard, but with the wordings above, it would not
> be needed.

Technically, it could still be wrapped if --max-error-line-width is set
low enough. There are other error messages built with error_specs as
well.

Peter

---

Shorten the "no targets specified" message.

Previously, when mmc --make did not have a target to make
it would print the error message:

** Error: no targets specified and `MAIN_TARGET' not defined.

Since commit c2be36780, it prints:

`mercury_compile': *** Error: no targets specified and `MAIN_TARGET' not
  defined.

Note the line break. This is due to constructing the message with
error_specs, which causes the message to be wrapped to the value of
--max-error-line-width. For various reasons, I find this undesirable.

compiler/make.top_level.m:
    Reword the error message so that it does not exceed the default
    value of --max-error-line-width. (This is far from a complete fix,
    of course.)

    Remove unnecessary quotes.

diff --git a/compiler/make.top_level.m b/compiler/make.top_level.m
index 0c959c3fe..e47b454a5 100644
--- a/compiler/make.top_level.m
+++ b/compiler/make.top_level.m
@@ -170,9 +170,9 @@ get_main_target_if_needed(ProgName, Variables, Targets0, MaybeTargets) :-
                 MaybeTargets = ok1(MainTargets)
             ;
                 MainTargets = [],
-                Pieces = [quote(ProgName), suffix(":"),
-                    words("*** Error: no targets specified and"),
-                    quote("MAIN_TARGET"), words("not defined."), nl],
+                Pieces = [fixed(ProgName), suffix(":"),
+                    words("*** Error: no target or MAIN_TARGET specified."),
+                    nl],
                 Spec = simplest_no_context_spec($pred, severity_error,
                     phase_options, Pieces),
                 MaybeTargets = error1([Spec])
-- 
2.38.0