----- Original Message ----- > From: "Guy Steele" <[email protected]> > To: "John Rose" <[email protected]> > Cc: "Tagir Valeev" <[email protected]>, "Brian Goetz" > <[email protected]>, "amber-spec-experts" > <[email protected]> > Sent: Wednesday, March 13, 2024 9:13:30 PM > Subject: Re: Update on String Templates (JEP 459)
>> On Mar 13, 2024, at 3:33 PM, John Rose <[email protected]> wrote: >> >> On 9 Mar 2024, at 3:48, Tagir Valeev wrote: >> >>> The idea is interesting. There's a thing that disturbs me though. >>> Currently, proc."string" and proc."string \{template}" are uniformly >>> processed, and the processor may not care much about whether it's a string >>> or a template: both can be processed uniformly. After this change, removing >>> the last embedded expression from the template (e.g., after inlining a >>> constant) will implicitly change the type of the literal from >>> StringTemplate to String. This may either cause a compilation error, or >>> silently bind to another overload which may or may not behave like a >>> template overload with a single-fragment-template. For API authors, this >>> means that every method accepting StringTemplate should have a counterpart >>> accepting String. The logic inside both methods would likely be very >>> similar, so probably both will eventually call a third private method. For >>> API user, it could be unclear how to call a method accepting StringTemplate >>> if I have simple string in hands but there's no String method (or it does >>> slightly different thing due to poor API design). Should I use some ugly >>> construct like "This is a string but the API wants a template, so I append >>> an empty embedded expression\{""}"? >> >> This is a huge thread that I hesitate to dive into, but here’s me putting in >> one >> toe: Why do we care so much about no-arg string templates? It’s a small >> corner case! The workarounds (for the no-arg case) are totally >> straightforward >> even if the string template literals (as a syntax) are required to have at >> least one argument. >> >> Can we have a plausible use case, please, for why a ST with no arguments >> would >> be important, so important that we are motived to invent a sigil syntax or >> special type system rules, to avoid requiring the user to invoke a static >> factory? >> >> Also, Tagir’s workaround of adding a fake argument looks like it would work >> just >> fine, of course depending on which processor was eventually used. >> >> And in that vein let me add one new (very bike-sheddy) suggestion before I >> beat >> a hasty retreat: Instead of in (1) a sigil before the quote like Guy’s >> $"hello", put it (1b) after the quote, and in the ST case only. The ST >> syntax >> could explicitly allow that a no-arg string template would be spelled with a >> leading sequence "\{}... which looks like the coder started writing a ST >> argument, but in fact dropped it. So "hello" is a 5-char string, in any >> context. And "\{}hello" is a 5-char no-arg string template, in any context. >> That’s Tagir’s workaround, elevated a bit into a new corner case of >> (existing) >> syntax. >> >> But even that teeny bit of syntax strikes me as overkill, because I don’t see >> the importance of the use cases (no-arg STs) it helps. Just call >> ST.of("hello") and call it a day. >> >> In any case, it seems fine to let the IDE take the lead with no-arg STs, >> helping >> the user decide when and how to disambiguate strings from no-arg STs. >> Putting >> in syntax or type system help for this is surely more expensive than punting >> to >> the IDE, unless there is going to be heavy use of no-arg STs for some use >> cases >> I am not seeing. > > Well, just off the top of my head as a thought experiment, if I had a series > of > SQL commands to process, some with arguments and some not, I would rather > write > > SQL.process($”CREATE TABLE foo;”); > SQL.process($”ALTER TABLE foo ADD name varchar(40);”); > SQL.process($”ALTER TABLE foo ADD title varchar(30);”); > SQL.process($”INSERT INTO foo (name, title) VALUES (‘Guy’, ‘Hacker’);”); > SQL.process($”INSERT INTO foo (name, title) VALUES (\{other name}, \{other > job});”); > > than > > SQL.process(ST.of(”CREATE TABLE foo;”)); > SQL.process(ST.of(”ALTER TABLE foo ADD name varchar(40);”)); > SQL.process(ST.of(”ALTER TABLE foo ADD title varchar(30);”)); > SQL.process(ST.of(”INSERT INTO foo (name, title) VALUES (‘Guy’, ‘Hacker’);”)); > SQL.process(”INSERT INTO foo (name, title) VALUES (\{other name}, \{other > job});”); > > especially if I thought that maybe down the road I might want to change the > constants 30 and 40 and ‘Hacker' to variables. I don't want to have to keep > adding and deleting calls to ST.of as I edit the template strings during > program development to have different numbers of interpolated expressions. Given what Maurizio said and this, i think the only missing piece in the puzzle is what about existing methods taking a String as parameter. We know that for SQL.process(), we do not want process() to take a String but only a StringTemplate. But what about the existing methods that takes a String. Given a method Logger.warning(String), should LOG.warning($”CREATE TABLE foo;”); LOG.warning($”INSERT INTO foo (name, title) VALUES (\{other name}, \{other job});”); be legal ? Is there an auto-conversion (a kind of boxing conversion) from StringTemplate to String ? > > —Guy Rémi
