I don't visually like ||/&& at start of line, but I can't fault the reasoning, so I'm weakly for it. I don't think it's important enough to change existing code though.
On Thu, Feb 16, 2017 at 1:47 PM, <gsquel...@mozilla.com> wrote: > Question of the day: > When breaking overlong expressions, should &&/|| go at the end or the > beginning of the line? > > TL;DR: Coding style says 'end', I&others think we should change it to > 'beginning' for better clarity, and consistency with other operators. > > > Our coding style reads: > "Break long conditions after && and || logical connectives. See below for the > rule for other operators." [1] > """ > Overlong expressions not joined by && and || should break so the operator > starts on the second line and starts in the same column as the start of the > expression in the first line. This applies to ?:, binary arithmetic operators > including +, and member-of operators (in particular the . operator in > JavaScript, see the Rationale). > > Rationale: operator at the front of the continuation line makes for faster > visual scanning, because there is no need to read to end of line. Also there > exists a context-sensitive keyword hazard in JavaScript; see bug 442099, > comment 19, which can be avoided by putting . at the start of a continuation > line in long member expression. > """ [2] > > > I initially focused on the rationale, so I thought *all* operators should go > at the front of the line. > > But it seems I've been living a lie! > &&/|| should apparently be at the end, while other operators (in some > situations) should be at the beginning. > > > Now I personally think this just doesn't make sense: > - Why the distinction between &&/|| and other operators? > - Why would the excellent rationale not apply to &&/||? > - Pedantically, the style talks about 'expression *not* joined by &&/||, but > what about expression that *are* joined by &&/||? (Undefined Behavior!) > > Based on that, I believe &&/|| should be made consistent with *all* > operators, and go at the beginning of lines, aligned with the first operand > above. > > And therefore I would propose the following changes to the coding style: > - Remove the lonely &&/|| sentence at [1]. > - Rephrase the first sentence at [2] to something like: "Overlong expressions > should break so that the operator starts on the following line, in the same > column as the first operand for that operator. This applies to all binary > operators, including member-of operators (in particular the . operator in > JavaScript, see the Rationale), and extends to ?: where the 2nd and third > operands should be on separate lines and start in the same column as the > first operand." > - Keep the rationale at [2]. > > Also, I think we should add something about where to break expressions with > operators of differing precedences, something like: "Overlong expressions > containing operators of differing precedences should first be broken at the > operator of lowest precedence. E.g.: 'a+b*c' should be split at '+' before > '*'" > > > A bit more context: > Looking at the history of the coding style page, a certain "Brendan" wrote > that section in August 2009 [3], shortly after a discussion here [4] that > seemed to focus on the dot operator in Javascript. In that discussion, &&/|| > appear in examples at the end of lines and nobody talks about that (because > it was not the main subject, and/or everybody agreed with it?) > > Discuss! > > > [1] > https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Coding_Style#Control_Structures > [2] > https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Coding_Style#Operators > [3] > https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Coding_Style$compare?locale=en-US&to=7315&from=7314 > [4] > https://groups.google.com/d/msg/mozilla.dev.platform/Ji9lxlLCYME/zabUmQI9S-sJ > _______________________________________________ > dev-platform mailing list > dev-platform@lists.mozilla.org > https://lists.mozilla.org/listinfo/dev-platform _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
